Abstract
This guide describes how to build and deploy AspectJ programs using the AspectJ tools and facilities. See also The AspectJ Programming Guide, the documentation available with the AspectJ support available for various integrated development environments (e.g., Eclipse AJDT), and the most-recent documentation available from the AspectJ project page, at http://eclipse.org/aspectj.
Table of Contents
List of Tables
List of Examples
Table of Contents
The AspectJ Programming Guide
describes the AspectJ language. This guide describes the AspectJ
tools produced by the AspectJ
team on
http://eclipse.org/aspectj.
The AspectJ tools include
- ajc, the compiler/weaver;
ajdoc, a documentation tool; ajbrowser, a crosscutting code viewer;
Ant support for ajc; and load-time weaving support.
These tools are delivered in the library folder of the AspectJ tools
installation, mainly in aspectjtools.jar
(tools) and
aspectjrt.jar
(runtime).
This guide does not describe the Eclipse AspectJ development tools
(AJDT). That is produced by another team (sharing some members) on
http://eclipse.org/ajdt.
AJDT is delivered as an Eclipse plugin, incorporating the classes in
the AspectJ tools libraries along with the Eclipse plugin interface
classes.
Since AspectJ 1.1, the tools have implemented the AspectJ language using bytecode weaving, which combines aspects and classes to produce .class files that run in a Java VM. There are other ways to implement the language (e.g., compiler preprocessor, VM support); the AspectJ team has always tried to distinguish the language and the implementation so other groups could build alternative implementations of AspectJ. To that end, The AspectJ Programming Guide, Implementation Notes describes how the Java bytecode form affects language semantics. VM- or source-based implementations may be free of these limits or impose limits of their own, but most should be fairly close to what's possible in Java bytecode.
Please be careful not to confuse any description of weaving or of this implementation of the AspectJ language with the AspectJ language semantics. If you do, you might find yourself writing code that doesn't work as expected when you compile or run it on other systems. More importantly, if you think about aspects in terms of weaving or of inserting or merging code, then you can lose many of the design benefits of thinking about an aspect as a single crosscutting module. When the text below introduces an implementation detail, it will warn if users make mistakes by applying it in lieu of the language semantics.
Bytecode weaving takes classes and aspects in .class form and weaves them together to produce binary-compatible .class files that run in any Java VM and implement the AspectJ semantics. This process supports not only the compiler but also IDE's. The compiler, given an aspect in source form, produces a binary aspect and runs the weaver. IDE's can get information about crosscutting in the program by subscribing to information produced by weaver as a side-effect of weaving.
Incremental compilation involves recompiling only what is necessary to bring the binary form of a program up-to-date with the source form in the shortest time possible. Incremental weaving supports this by weaving on a per-class basis. (Some implementations of AOP (including AspectJ 1.0) make use of whole-program analysis that can't be done in incremental mode.) Weaving per-class means that if the source for a pure Java class is updated, only that class needs to be produced. However, if some crosscutting specification may have been updated, then all code potentially affected by it may need to be woven. The AspectJ tools are getting better at minimizing this effect, but it is to some degree unavoidable due to the crosscutting semantics.
Memory usage can seem higher with AspectJ tools. Some aspects are written to potentially affect many classes, so each class must be checked during the process of weaving. Programmers can minimize this by writing the crosscutting specifications as narrowly as possible while maintaining correctness. (While it may seem like more memory, the proper comparison would with with a Java program that had the same crosscutting, with changes made to each code segment. That would likely require more memory and more time to recompile than the corresponding AspectJ program.)
AspectJ introduces two new paths for the binary input to the weaver which you'll find referenced in The ajc Command-line Reference, AspectJ Browser, AspectJ Ant Tasks, and Load-Time Weaving.
As in Java, the classpath
is where the AspectJ
tools resolve types specified in the program. When running an AspectJ
program, the classpath should contain the classes and aspects along with
the AspectJ runtime library, aspectjrt.jar
.
In AspectJ tools, the aspectpath
is where to find binary
aspects. Like the classpath, it can include archives (.jar and .zip files)
and directories containing .class files in a package layout (since
binary aspects are in .class files). These aspects affect other
classes in exactly the same way as source-level aspects, but are themselves
not affected. When deploying programs, the original aspects must be included
on the runtime classpath.
In AspectJ tools, the inpath
is where to find binary
input - aspects and classes that weave and may be woven.
Like the classpath, it can include archives and class directories.
Like the aspectpath, it can include aspects that affect other classes
and aspects.
However, unlike the aspectpath, an aspect on the inpath may itself be
affected by aspects, as if the source were all compiled together.
When deploying aspects that were put on the inpath, only the woven output
should be on the runtime classpath.
Although types in the inpath and the aspectpath need to be resolved by
the AspectJ tools, you usually do not need to place them on the classpath
because this is done automatically by the compiler/weaver. But when using
the WeavingURLClassLoader
, your code must explicitly add the aspects
to the classpath so they can be resolved (as you'll see in the sample
code and the aj.bat
script).
The most common mistake is failing to add
aspectjrt.jar
to the classpath. Also, when
weaving with binary aspects, users forget to deploy the aspect itself
along with any classes it requires. A more subtle mistake is putting a
binary aspect (BA) on the inpath instead of the aspectpath. In this case
the aspect BA might be affected by an aspect, even itself; this can
cause the program to fail, e.g., when an aspect uses exclusion to
avoid infinite recursion but fails to exclude advice in aspect BA.
The latter is one of many ways that mistakes in the build process can affect aspects that are written poorly. Aspects should never rely on the boundaries of the build specification to narrow the scope of their crosscutting, since the build can be changed without notice to the aspect developer. Careful users might even avoid relying on the implementation scope, to ensure their AspectJ code will run on other implementations.
Table of Contents
ajc — compiler and bytecode weaver for the AspectJ and Java languages
ajc
[Options
] [[file...
] | [@file...
] | [-argfile file...
]]
The ajc command compiles and weaves AspectJ and Java source and .class files, producing .class files compliant with any Java VM (1.1 or later). It combines compilation and bytecode weaving and supports incremental builds; you can also weave bytecode at run-time using Load-Time Weaving.
The arguments after the options specify the source file(s) to compile.
To specify source classes, use -inpath
(below).
Files may be listed directly on the command line or in a file.
The -argfile
and file
@
forms
are equivalent, and are interpreted as meaning all the arguments
listed in the specified file.
file
Note: You must explicitly pass ajc all necessary sources. Be sure to include the source not only for the aspects or pointcuts but also for any affected types. Specifying all sources is necessary because, unlike javac, ajc does not search the sourcepath for classes. (For a discussion of what affected types might be required, see The AspectJ Programming Guide, Implementation Appendix.)
To specify sources, you can list source files as arguments or use the
options -sourceroots
or -inpath
.
If there are multiple sources for any type, the result is undefined
since ajc has no way to determine which source is correct. (This
happens most often when users include the destination directory
on the inpath and rebuild.)
JarList
deprecated: since 1.2, use -inpath, which also takes directories.
Path
Accept as source bytecode any .class files in the .jar files or directories on Path. The output will include these classes, possibly as woven with any applicable aspects. Path is a single argument containing a list of paths to zip files or directories, delimited by the platform-specific path delimiter.
Path
Weave binary aspects from jar files and directories on path into all sources. The aspects should have been output by the same version of the compiler. When running the output classes, the run classpath should contain all aspectpath entries. Path, like classpath, is a single argument containing a list of paths to jar files, delimited by the platform- specific classpath delimiter.
File
The file contains a line-delimited list of arguments.
Each line in the file should contain one option, filename, or
argument string (e.g., a classpath or inpath).
Arguments read from the file are inserted into the argument list
for the command. Relative paths in the file are calculated from
the directory containing the file (not the current working directory).
Comments, as in Java, start with //
and
extend to the end of the line. Options specified in argument
files may override rather than extending existing option values,
so avoid specifying options like -classpath
in argument files unlike the argument file is the only build
specification. The form @file
is the same
as specifying -argfile file
.
output.jar
Put output classes in zip file output.jar.
Generate aop.xml file for load-time weaving with default name.
custom/aop.xml
Generate aop.xml file for load-time weaving with custom name.
Run the compiler continuously. After the initial compilation, the compiler will wait to recompile until it reads a newline from the standard input, and will quit when it reads a 'q'. It will only recompile necessary components, so a recompile should be much faster than doing a second compile. This requires -sourceroots.
DirPaths
Find and build all .java or .aj source files under any directory listed in DirPaths. DirPaths, like classpath, is a single argument containing a list of paths to directories, delimited by the platform- specific classpath delimiter. Required by -incremental.
Generate a build .ajsym file into the output directory. Used for viewing crosscutting references by tools like the AspectJ Browser.
Generate .ajesym symbol files for emacs support (deprecated).
Same as -Xlint:warning (enabled by default)
Set default level for messages about potential programming mistakes in crosscutting code. {level} may be ignore, warning, or error. This overrides entries in org/aspectj/weaver/XlintDefault.properties from aspectjtools.jar, but does not override levels set using the -Xlintfile option.
PropertyFile
Specify properties file to set levels for specific crosscutting messages. PropertyFile is a path to a Java .properties file that takes the same property names and values as org/aspectj/weaver/XlintDefault.properties from aspectjtools.jar, which it also overrides.
Emit information on compiler options and usage
Emit the version of the AspectJ compiler
Path
Specify where to find user class files. Path is a single argument containing a list of paths to zip files or directories, delimited by the platform-specific path delimiter.
Path
Override location of VM's bootclasspath for purposes of evaluating types when compiling. Path is a single argument containing a list of paths to zip files or directories, delimited by the platform-specific path delimiter.
Path
Override location of VM's extension directories for purposes of evaluating types when compiling. Path is a single argument containing a list of paths to directories, delimited by the platform-specific path delimiter.
Directory
Specify where to place generated .class files.
If not specified, Directory
defaults to the current working dir.
[1.1 to 1.5]
Specify classfile target setting (1.1 to 1.5, default is 1.2)
Set compliance level to 1.3 This implies -source 1.3 and -target 1.1.
Set compliance level to 1.4 (default) This implies -source 1.4 and -target 1.2.
Set compliance level to 1.5. This implies -source 1.5 and -target 1.5.
[1.3|1.4|1.5]
Toggle assertions (1.3, 1.4, or 1.5 - default is 1.4).
When using -source 1.3, an assert() statement valid under
Java 1.4 will result in a compiler error.
When using -source 1.4,
treat assert
as a keyword and
implement assertions according to the 1.4 language spec.
When using -source 1.5,
Java 5 language features are permitted.
Emit no warnings (equivalent to '-warn:none')
This does not suppress messages
generated by declare warning
or
Xlint
.
items
Emit warnings for any instances of the comma-delimited list of questionable code (eg '-warn:unusedLocals,deprecation'):
constructorName method with constructor name packageDefaultMethod attempt to override package-default method deprecation usage of deprecated type or member maskedCatchBlocks hidden catch block unusedLocals local variable never read unusedArguments method argument never read unusedImports import statement not used by code in file none suppress all compiler warnings
-warn:none
does not suppress messages
generated by declare warning
or
Xlint
.
Same as -warn:deprecation
Emit no errors for unresolved imports
Keep compiling after error, dumping class files with problem methods
:[lines,vars,source]
debug attributes level, that may take three forms:
-g all debug info ('-g:lines,vars,source') -g:none no debug info -g:{items} debug info for any/all of [lines, vars, source], e.g., -g:lines,source
Preserve all local variables during code generation (to facilitate debugging).
Compute reference information.
format
Specify default source encoding format. Specify custom encoding on a per file basis by suffixing each input source file/folder name with '[encoding]'.
Emit messages about accessed/processed compilation units
Emit messages about weaving
file
Specify a log file for compiler messages.
Show progress (requires -log mode).
Display speed information.
Do not call System.exit(n) at end of compilation (n=0 if no error)
N
Repeat compilation process N times (typically to do performance analysis).
Causes compiler to terminate before weaving
Causes the compiler to calculate and add the SerialVersionUID field to any type implementing Serializable that is affected by an aspect. The field is calculated based on the class before weaving has taken place.
(Experimental - deprecated as now default) Runs weaver in reweavable mode which causes it to create woven classes that can be rewoven, subject to the restriction that on attempting a reweave all the types that advised the woven type must be accessible.
(Experimental) do not inline around advice
file
(Experimental) This works like incremental mode, but using a file rather than standard input to control the compiler. It will recompile each time file is changed and and halt when file is deleted.
(Experimental) Normally it is an error to declare aspects Serializable. This option removes that restriction.
(Experimental) Create class files that can't be subsequently rewoven by AspectJ.
(Experimental) Allows code to be generated that targets a 1.2 or a 1.5 level AspectJ runtime (default 1.5)
ajc accepts source files with either the .java
extension or the .aj
extension. We normally use
.java
for all of our files in an AspectJ system -- files
that contain aspects as well as files that contain classes. However, if
you have a need to mechanically distinguish files that use AspectJ's
additional functionality from those that are pure Java we recommend using
the .aj
extension for those files.
We'd like to discourage other means of mechanical distinction such as
naming conventions or sub-packages in favor of the .aj
extension.
Filename conventions are hard to enforce and lead to awkward names
for your aspects. Instead of TracingAspect.java
we
recommend using Tracing.aj
(or just
Tracing.java
) instead.
Sub-packages move aspects out of their natural place in a system
and can create an artificial need for privileged aspects. Instead of
adding a sub-package like aspects
we recommend using the
.aj
extension and including these files in your existing
packages instead.
AspectJ is a compatible extension to the Java programming language. The AspectJ compiler adheres to the The Java Language Specification, Second Edition and to the The Java Virtual Machine Specification, Second Edition and runs on any Java 2 compatible platform. The code it generates runs on any Java 1.1 or later compatible platform. For more information on compatibility with Java and with previous releases of AspectJ, see AspectJ Version Compatibility.
Example 2.2. An example using -argfile/@
To avoid specifying file names on the command line,
list source files in a line-delimited text argfile.
Source file paths may be absolute or relative to the argfile,
and may include other argfiles by @-reference.
The following file sources.lst
contains absolute and relative files and @-references:
Gui.java /home/user/src/Library.java data/Repository.java data/Access.java @../../common/common.lst @/home/user/src/lib.lst view/body/ArrayView.java
Compile the files using either the -argfile or @ form:
ajc -argfile sources.lst ajc @sources.lst
Argfiles are also supported by jikes and javac, so you can use the files in hybrid builds. However, the support varies:
Only ajc accepts command-line options
Jikes and Javac do not accept internal @argfile references.
Jikes and Javac only accept the @file form on the command line.
Example 2.3. An example using -inpath and -aspectpath
Bytecode weaving using -inpath: AspectJ 1.2 supports weaving .class files in input zip/jar files and directories. Using input jars is like compiling the corresponding source files, and all binaries are emitted to output. Although Java-compliant compilers may differ in their output, ajc should take as input any class files produced by javac, jikes, eclipse, and, of course, ajc. Aspects included in -inpath will be woven into like other .class files, and they will affect other types as usual.
Aspect libraries using -aspectpath: AspectJ 1.1 supports weaving from read-only libraries containing aspects. Like input jars, they affect all input; unlike input jars, they themselves are not affected or emitted as output. Sources compiled with aspect libraries must be run with the same aspect libraries on their classpath.
The following example builds the tracing example in a command-line environment; it creates a read-only aspect library, compiles some classes for use as input bytecode, and compiles the classes and other sources with the aspect library.
The tracing example is in the AspectJ distribution ({aspectj}/doc/examples/tracing). This uses the following files:
aspectj1.1/ bin/ ajc lib/ aspectjrt.jar examples/ tracing/ Circle.java ExampleMain.java lib/ AbstractTrace.java TraceMyClasses.java notrace.lst Square.java tracelib.lst tracev3.lst TwoDShape.java version3/ Trace.java TraceMyClasses.java
Below, the path separator is taken as ";", but file separators are "/". All commands are on one line. Adjust paths and commands to your environment as needed.
Setup the path, classpath, and current directory:
cd examples export ajrt=../lib/aspectjrt.jar export CLASSPATH="$ajrt" export PATH="../bin:$PATH"
Build a read-only tracing library:
ajc -argfile tracing/tracelib.lst -outjar tracelib.jar
Build the application with tracing in one step:
ajc -aspectpath tracelib.jar -argfile tracing/notrace.lst -outjar tracedapp.jar
Run the application with tracing:
java -classpath "$ajrt;tracedapp.jar;tracelib.jar" tracing.ExampleMain
Build the application with tracing from binaries in two steps:
(a) Build the application classes (using javac for demonstration's sake):
mkdir classes javac -d classes tracing/*.java jar cfM app.jar -C classes .
(b) Build the application with tracing:
ajc -inpath app.jar -aspectpath tracelib.jar -outjar tracedapp.jar
Run the application with tracing (same as above):
java -classpath "$ajrt;tracedapp.jar;tracelib.jar" tracing.ExampleMain
Run the application without tracing:
java -classpath "app.jar" tracing.ExampleMain
The AspectJ compiler is implemented completely in Java and can be
called as a Java class. The only interface that should be considered
public are the public methods in org.aspectj.tools.ajc.Main
.
E.g., main(String[] args)
takes the
the standard ajc command line arguments.
This means that an alternative way to run the
compiler is
[java org.aspectj.tools.ajc.Main
option...
] [file...
]
To access compiler messages programmatically, use the methods
setHolder(IMessageHolder holder)
and/or
run(String[] args, IMessageHolder holder)
.
ajc
reports each message to the holder
using IMessageHolder.handleMessage(..)
.
If you just want to collect the messages, use
MessageHandler
as your
IMessageHolder
.
For example, compile and run the following with
aspectjtools.jar
on the classpath:
import org.aspectj.bridge.*; import org.aspectj.tools.ajc.Main; import java.util.Arrays; public class WrapAjc { public static void main(String[] args) { Main compiler = new Main(); MessageHandler m = new MessageHandler(); compiler.run(args, m); IMessage[] ms = m.getMessages(null, true); System.out.println("messages: " + Arrays.asList(ms)); } }
Unlike traditional java compilers, the AspectJ compiler may in certain cases generate classfiles from multiple source files. Unfortunately, the original Java class file format does not support multiple SourceFile attributes. In order to make sure all source file information is available, the AspectJ compiler may in some cases encode multiple filenames in the SourceFile attribute. When the Java VM generates stack traces, it uses this attribute to specify the source file.
(The AspectJ 1.0 compiler also supports the .class file extensions of JSR-45. These permit compliant debuggers (such as jdb in Java 1.4.1) to identify the right file and line even given many source files for a single class. JSR-45 support is planned for ajc in AspectJ 1.1, but is not in the initial release. To get fully debuggable .class files, use the -XnoInline option.)
Probably the only time you may see this format is when you view stack traces, where you may encounter traces of the format
java.lang.NullPointerException at Main.new$constructor_call37(Main.java;SynchAspect.java[1k]:1030)
where instead of the usual
File:LineNumber
format, you see
File0;File1[Number1];File2[Number2] ... :LineNumber
In this case, LineNumber is the usual offset in lines plus the "start line" of the actual source file. That means you use LineNumber both to identify the source file and to find the line at issue. The number in [brackets] after each file tells you the virtual "start line" for that file (the first file has a start of 0).
In our example from the null pointer exception trace, the virtual start line is 1030. Since the file SynchAspect.java "starts" at line 1000 [1k], the LineNumber points to line 30 of SynchAspect.java.
So, when faced with such stack traces, the way to find the actual source location is to look through the list of "start line" numbers to find the one just under the shown line number. That is the file where the source location can actually be found. Then, subtract that "start line" from the shown line number to find the actual line number within that file.
In a class file that comes from only a single source file, the AspectJ compiler generates SourceFile attributes consistent with traditional Java compilers.
ajdoc
produces JavaDoc-style documentation
including crosscutting information.
ajdoc — generate HTML API documentation, including crosscutting structure
ajdoc
[
-bootclasspath classpathlist
] [
-classpath classpathlist
] [-d path
] [-help] [-package] [-protected] [-private] [-public] [-overview overviewFile
] [
-sourcepath sourcepathlist
] [-verbose] [-version] [[sourcefiles...
] | [packages...
] | [@file...
] | [-argfile file...
]] [
ajc options
]
ajdoc renders HTML documentation for AspectJ constructs as well as the Java constructs that javadoc renders. In addition ajdoc displays the crosscutting nature in the form of links. That means, for example, that you can see everything affecting a method when reading the documentation for the method.
To run ajdoc, use one of the scripts in the
AspectJ bin
directory.
The ajdoc implementation builds on Sun's javadoc
command line tool, and you use it in the same way with many of
the same options
(javadoc options are not documented here;
for more information on javadoc usage, see the
Javadoc homepage.)
As with ajc (but unlike javadoc),
you pass ajdoc all your aspect source files
and any files containing types affected by the aspects;
it's often easiest to just pass all the .java
and .aj
files in your system.
Unlike ajc,
ajdoc will try to find package sources using the
specified sourcepath if you list packages on the command line.
To provide an argfile listing the source files, you can use
use the same argfile (@filename
) conventions
as with ajc.
For example, the following documents all the source files listed
in argfile.lst
, sending the output to
the docDir
output directory.
ajdoc -d docDir @argfile.lst
See the ajc documentation for details on the text file format.
ajdoc honours ajc options. See the ajc documentation for details on these options.
ajdoc currently requires the
tools.jar
from J2SE 1.3 to be on the classpath.
Normally the scripts set this up, assuming that your JAVA_HOME
variable points to an appropriate installation of Java.
You may need to provide this jar when using a different
version of Java or a JRE.
Example 2.4. Documenting Spacewar
Change into the examples
directory.
Type mkdir doc
to create the
destination directory for the documentation.
Type ajdoc -private -d doc spacewar
coordination
to generate the documentation.
(Use -private
to get all members, since
may of the interesting ones in spacewar are not public.)
Type ajdoc -private -d doc @spacewar/demo.lst
to use the argfile associated with Spacewar.
To view the documentation, open the file index.html
in the doc
directory using a web browser.
aj
launches programs,
configuring basic load-time weaving.
aj — command-line launcher for basic load-time weaving
aj
[Options
] [[arg...
]]
The
aj command runs Java programs in Java 1.4 or
later by setting up
WeavingURLClassLoader
as the system class
loader, to do load-time bytecode weaving.
The arguments are the same as those used to launch the Java program.
Users should define the environment variables
CLASSPATH
and
ASPECTPATH
.
For more information and alternatives for load-time weaving, see Load-Time Weaving.
Example 2.5. A simple example
Use ajc to build a library, then weave at load time
REM compile library ${ASPECTJ_HOME}\bin\ajc.bat -outjar lib\aspects.jar @aspects.lst REM run, weaving into application at load-time set ASPECTPATH=lib\aspects.jar set CLASSPATH=app\app.jar ${ASPECTJ_HOME}\bin\aj.bat com.company.app.Main "Hello, World!"
Table of Contents
AJBrowser presents a GUI for compiling programs with ajc and navigating crosscutting structure.
The AspectJ Browser can edit program source files,
compile using the AspectJ compiler ajc
run a program,
and graphically navigate the program's
crosscutting structure.
For more information on ajc
,
see The ajc Command-line Reference.
Launch the browser from the command line either
by typing "ajbrowser" to invoke the script in
{aspectj}/bin
(if AspectJ is installed correctly)
or by using the
aspectjtools.jar
directly,
and specifying no arguments or some number of
build configuration files
(suffix .lst
):
java -jar aspectj1.1/lib/aspectjtools.jar aspectj1.1/doc/examples/spacewar/debug.lst
A build configuration is a set of files to compile for a
program (and optionally some additional compile arguments).
Because ajc
requires all sources to be specified
(at least using the -sourceroots
option),
most users create .lst
files that list
the files to compile (one argument per line, globbing
permitted - for more details, see The ajc Command-line Reference).
To work with a particular program, select the
corresponding ".lst" build configuration file
from the GUI using the File menu, "open" item,
or by using the
"Open Build Configuration" button
().
You can populate the build list from the command line
by passing any number of ".lst" paths.
(However, if you pass in any non-".lst" arguments,
it will run the command-line compiler directly.)
To switch between build configurations, select, add, or remove them using the corresponding toolbar buttons.
Global build options are stored in an
.ajbrowser
file in your HOME directory.
Edit these from the GUI by clicking the "Options" button
or selecting the Tools menu item "Options...".
This is how to set classpath, aspectpath, etc.
The following sections walk through a build.
Select nodes in the program structure by clicking them (see label 2).
If one node is related to one or more other nodes by an association the
name of the association will appear below that node and will be
displayed in italics. Links to other structure nodes appear in blue
below the association. If there is no corresponding source for the
link it will appear light-blue.
Launch ajbrowser
Choose "File -> Open" or click the "Open Build
Configuration" button
() and select the configuration file for debugging
the spacewar example, in
examples/spacewar/debug.lst
.
Click the "Build" button () to
compile. The left pane should fill with a spacewar declaration
tree. If there is a compiler error, the clickable error message
shows up as in label 4.
Note: If you did not set up your classpath, the
compile will fail with a message that you need to install
aspectjrt.jar on your compile classpath. To do that, select "Tools
-> Options" or click the "Options" button
(). Click the
Build Options
tab
to view the Build Paths pane. Edit the classpath entry to use your
install location. For example, if you ran from the base Aspectj
directory, the classpath need only include
lib/aspectjrt.jar
(though the browser may populate
the classpath with the bootclasspath and classpath initially.)
Be sure to use the
lib/aspectjrt.jar
that came with the browser.
>
Different structure views: The structure tree at the left can display different orderings and granularity for structure:
The package hierarchy view shows the traditional hierarchy of package, class, and members.
The inheritance view shows the hierarchy from topmost parent classes through subclasses to members.
The crosscutting view shows the aspect members and the code they affect.
Additional buttons in the pane can be used to change the granularity and filter out items.
Whenever you select an item in the tree view, the source pane scrolls to that item. If you select a leaf item representing another program element, then the tree selection will go to the corresponding node. (See below for how to use two panes to maintain your place.)
When working with aspects, it helps to be able to navigate between different program elements:
When looking at a method, find the advice that affects it.
When looking at a pointcut, find the advice that uses it.
When looking at advice, find what it advises - e.g., method calls or executions, initializers, etc.
When looking at a type, find any aspects that declare members or supertypes of the type, or vice-versa.
You can view the advice on a particular method using the
default, hierarchical view. Navigate to the tree item for
spacewar.Registry.register(SpaceObject)
in the debug.lst
config file. Now, in
the lower, file view, you can see and navigate to the advice
using the subtree whose parent is the method
affected by
relation.
You can also use crosscutting view to see the
advice using a pointcut or the methods affected by advice.
For example, to see what advice uses a particular pointcut,
navigate to the tree item for the pointcut
spacewar.Debug.allConstructorsCut()
in
the debug.lst
config file. You can see
and navigate to the advice that uses the pointcut using the
pointcut used by
relation.
As an example of seeing the methods affected by advice,
while still in the same view, select the first
before
advice in
spacewar.Debug
. It has relation
sub-trees for both uses pointcut
and
affects constructions
. The
affects
relations will list different
kinds of join points - constructor or method calls, etc.
Note that the AspectJ browser can only display
static structure (whether hierarchical or crosscutting).
That means that dynamicly-determined pointcuts (like
cflow(pointcut)
)
will not be shown as picking out static points in
source code. Displayable pointcuts roughly correspond
to those that can be used in a
declare error
statement.
The browser supports a limited form of running compiled programs. To run programs that have been built, click the run button or select one of the run menu items in the project menu. You can run in the same VM or spawn a new process; the latter is generally better for GUI programs.
Both require that any classpath you set be specified using platform-specific paths and path separators (the compiler might be more tolerant). Output and error streams will be merged into the streams of the browser (using separate threads, so it may take a few seconds for the pipe threads to gain control.) Errors should be detected and displayed in a dialog.
The GUI does not support killing a running program, so if your program might hang, be sure to save your files since you may need to kill the browser itself to kill its child processes.
If you have problems with the browser not solved by the documentation, please try to see if you have the same problems when running ajc directly on the command line.
If the problem occurs on the command line also, then the problem is not in the browser. (It may be in the compiler; please send bug reports.)
If the problem does not occur on the command line, then it may lie in the parameters you are supplying in the build options.
If the build options look correct and the problem only occurs when building from the browser, then please submit a bug report.
For the most up-to-date information on known problems, see the bug database for unresolved compiler bugs or IDE bugs .
Memory and forking: Users email most about the browser task running out of memory. This is not a problem with the browser; some compiles take a lot of memory, often more than similar compiles using javac. The browser does not support forking, so the only solution is to edit the java command line or script that launches the browser to add memory.
Editing build configuration files: this is not currently supported.
The structure model is incomplete after incremental compiles. To get a complete structure model requires a full build.
If you change the output directory, you must do a full build.
The AJBrowser expects the package and directory structure to match. If they do not it will be unable to browse to the corresponding file.
The "Run" feature launches applications in the same VM. As a result, if a Swing application is disposed the AJBrowser will be disposed as well.
You can send email to aspectj-users@dev.eclipse.org. (Do join the list to participate!) We also welcome any bug reports, patches, and feature requests; you can submit them to the bug database at http://bugs.eclipse.org/bugs using the AspectJ product and IDE component.
Table of Contents
AspectJ contains a compiler, ajc
,
that can be run from Ant.
Included in the aspectjtools.jar
are Ant binaries to support three
ways of running the compiler:
AjcTask (iajc), a task to run the AspectJ post-1.1 compiler, which supports all the eclipse and ajc options, including incremental mode.
Ajc11CompilerAdapter (javac), an adapter class to run the new compiler using Javac tasks by setting the build.compiler property
Ajc10 (ajc), a task to run build scripts compatible with the AspectJ 1.0 tasks
This describes how to install and use the tasks and the adapter. For an example Ant script, see examples/build.xml.
Install Jakarta Ant 1.5.1: Please see the official Jakarta Ant website for more information and the 1.5.1 distribution. This release is source-compatible with Ant 1.3 and Ant 1.4, but the task sources must be compiled with those versions of the Ant libraries to be used under those versions of Ant. Sources are available under the Eclipse Public License v. 1.0 at http://eclipse.org/aspectj.
In Ant 1.5, third-party tasks can be declared using a taskdef entry in
the build script, to identify the name and classes.
When declaring a task, include the
aspectjtools.jar
either in the
taskdef classpath or in ${ANT_HOME}/lib
where it will be added
to the system class path by the ant script.
You may specify the task script names directly,
or use the "resource" attribute to specify the default names:
<taskdef resource="org/aspectj/tools/ant/taskdefs/aspectjTaskdefs.properties"/>
The current resource file retains the name "ajc" for the Ajc10 task, and uses "iajc" for the AspectJ post-1.1 task.
In Ant 1.6, third-party tasks are declared in their own namespace
using antlib.xml
. For example, the following
script would build and run the spacewar example, if you put the
script in the examples directory and aspectjtools.jar
in the ${ANT_HOME}/lib
directory.
<project name="aspectj-ant1.6" default="spacewar" xmlns:aspectj="antlib:org.aspectj" basedir="."> <target name="spacewar"> <aspectj:iajc argfiles="spacewar/debug.lst" outjar="spacewar.jar" classpath="../../lib/aspectjrt.jar" /> <java classname="spacewar.Game" classpath="spacewar.jar:../../lib/aspectjrt.jar"/> </target> </project>
For more information on using Ant, please refer to Jakarta's documentation on integrating user-defined Ant tasks into builds.
This task uses the AspectJ post-1.1 compiler ajc. The AspectJ compiler can be used like Javac to compile Java sources, but it can also compile AspectJ sources or weave binary aspects with Java bytecode. It can run in normal "batch" mode or in an "incremental" mode, where it only recompiles files it has to revisit. For more information on ajc, see The ajc Command-line Reference. Unlike Javac or the Javac Ant task, this task always compiles the specified files since aspects can apply to other (updated) files. For a workaround, see Avoiding clean compiles.
Beyond the normal ajc compiler options, this task also supports an experimental option for an incremental "tag" file, and it can copy resources from source directories or input jars to the output jar or directory.
This task is named iajc to avoid conflict with the 1.0 task ajc.
The following tables list the supported parameters. For any parameter specified as a Path, a single path can be specified directly as an attribute, multiple paths can be specified using a nested element of the same name, and a common path can be reused by defining it as a global and passing the id to the corresponding {name}ref attribute. See Path below for more details.
Most attributes and nested elements are optional.
The compiler requires that the same version of
aspectjrt.jar
be specified on the classpath, and that some sources be
be specified
(using one or more of
sourceroots
,
injars
,
inpath
,
argfiles
, and/or
srcdir
(with patterns)).
When in incremental mode, only
sourceroots
may be specified.
Boolean parameters default to false
unless otherwise stated.
AjcTask (iajc) options for specifying sources
Attribute | Description |
---|---|
argfiles, argfilesRef (Path) | An argument file contains a list of arguments read by the compiler. Each line is read into one element of the argument array and may include another argfile by reference. |
sourceRoots, sourceRootsRef (Path) | Directories containing source files (ending with .java or .aj) to compile. |
srcdir (Path) | Base directory of sources to compile, assuming there are nested matches. This approach uses the Ant process for matching .java files and is not compatible with incremental mode. Unless using filters to limit the sources included, use sourceroots instead. |
injars, injarsRef (Path) | Deprecated - use inpath instead. Read .class files for bytecode weaving from zip files (only). |
inpath, inpathRef (Path) | Read .class files for bytecode weaving from directories or zip files (like classpath). |
classpath, classpathRef (Path) |
The classpath used by the sources being compiled.
When compiling aspects, include the same version of the
|
bootclasspath, bootclasspathRef (Path) | The bootclasspath specifies types to use instead of the invoking VM's when seeking types during compilation. |
extDirs, extDirsRef (Path) | The extension directories to use instead of those in the invoking VM when seeking types during compilation. |
aspectPath, aspectPathRef (Path) |
Similar to classpath, aspectpath contains read-only,
binary aspect libraries that are woven into sources
but not included in the output.
|
AjcTask (iajc) options for specifying output
Attribute | Description |
---|---|
destDir |
The directory in which to place the generated class files.
Only one of |
outJar |
The zip file in which to place the generated output class files.
Only one of |
copyInjars | (Deprecated/ignored; ajc does this.) If true, copy all non-.class files from input jar(s) to the output jar or destination directory after the compile (or incremental compile) completes. In forked mode, this copies only after the process completes, not after incremental compiles. |
sourceRootCopyFilter |
When set, copy all files from the sourceroot directories to the output jar
or destination directory except those specified in the filter pattern.
The pattern should be compatible with an Ant fileset excludes filter;
when using this, most developers pass
|
inpathDirCopyFilter |
When set, copy all files from the inpath directories
to the output jar or destination directory except those
specified in the filter pattern. The pattern should be
compatible with an Ant fileset excludes filter; when
using this, most developers pass
|
AjcTask (iajc) options for specifying compiler behavior
Attribute | Description |
---|---|
fork |
Run process in another VM.
This gets the forking classpath either explicitly
from a |
forkclasspath, forkclasspathRef (Path) | Specify the classpath to use for the compiler when forking. |
maxmem | The maximum memory to use for the new VM when fork is true. Values should have the same form as accepted by the VM, e.g., "128m". |
incremental |
incremental mode: Build once, then recompile only required source
files when user provides input.
Requires that source files be specified only using
|
tagfile |
incremental mode: Build once, then recompile only required source
files when the tag file is updated, finally exiting when tag file
is deleted.
Requires that source files be specified only using
|
X | Set experimental option(s), using comma-separated list of accepted options Options should not contain the leading X. Some commonly-used experimental options have their own entries. The other permitted ones (currently) are serializableAspects, incrementalFile, lazyTjp, reweavable, notReweavable, noInline, terminateAfterCompilation, ajruntimelevel:1.2, and ajruntimelevel:1.5. Of these, some were deprecated in AspectJ 5 (reweavable, terminateAfterCompilation, etc.). |
XterminateAfterCompilation | Terminates before the weaving process, dumping out unfinished class files. |
AjcTask (iajc) options for specifying compiler side-effects and messages
Attribute | Description |
---|---|
emacssym |
If true, emit |
crossref |
If true, emit |
verbose | If true, log compiler verbose messages as Project.INFO during the compile. |
logCommand | If true, log compiler command elements as Project.INFO (rather than the usual Project.VERBOSE level). |
Xlistfileargs | If true, emit list of file arguments during the compile (but behaves now like verbose). |
version | If true, do not compile - just print AspectJ version. |
help | If true, just print help for the command-line compiler. |
Xlintwarnings |
Same as |
Xlint |
Specify default level of all language usage messages to one of
[ |
XlintFile |
Specify property file containing |
failonerror |
If true, throw BuildException to halt build if there
are any compiler errors.
If false, continue notwithstanding compile errors.
Defaults to |
messageHolderClass |
Specify a class to use as the message holder for the compile process.
The entry must be a fully-qualified name of a class resolveable from
the task classpath complying with the
|
showWeaveInfo |
If true, emit weaver messages.
Defaults to |
AjcTask (iajc) options for specifying Eclipse compiler options
Attribute | Description |
---|---|
nowarn |
If true, same as |
deprecation |
If true, same as |
warn |
One or more comma-separated warning specifications from
[ |
debug |
If true, same as |
debugLevel |
One or more comma-separated debug specifications from
[ |
PreserveAllLocals | If true, code gen preserves all local variables (for debug purposes). |
noimporterror | If true, emit no errors for unresolved imports. |
referenceinfo | If true, compute reference info. |
log | File to log compiler messages to. |
encoding | Default source encoding format (per-file encoding not supported in Ant tasks). |
proceedOnError | If true, keep compiling after errors encountered, dumping class files with problem methods. |
progress | If true, emit progress (requires log). |
time | If true, display speed information. |
target |
Specify target class file format as one of
[ |
source |
Set source compliance level to one of
[ |
source |
Set source assertion mode to one of
[ |
This task forms an implicit FileSet and supports all attributes of
<fileset>
(dir becomes srcdir) as well as
the nested
<include>
,
<exclude>
, and
<patternset>
elements.
These can be used to specify source files.
However, it is better to use sourceroots
to specify source directories unless using filters to exclude
some files from compilation.
Some parameters are path-like structures containing one or more
elements; these are
sourceroots
,
argfiles
,
injars
,
inpath
,
classpath
,
bootclasspath
,
forkclasspath
, and
aspectpath
.
In all cases, these may be specified as nested elements, something
like this:
<iajc {attributes..} /> <{name}> <pathelement path="{first-location}"/> <pathelement path="{second-location}"/> ... <{name}> ... </iajc>
As with other Path-like structures, they may be defined elsewhere and specified using the refid attribute:
<path id="aspect.path"> <pathelement path="${home}/lib/persist.jar"/> <pathelement path="${home}/lib/trace.jar"/> </path> ... <iajc {attributes..} /> <aspectpath refid="aspect.path"/> ... </iajc>
The task also supports an attribute {name}ref
for each such parameter. E.g., for aspectpath
:
<iajc {attributes..} aspectpathref="aspect.path"/>
A minimal build script defines the task and runs it, specifying the sources:
<project name="simple-example" default="compile" > <taskdef resource="org/aspectj/tools/ant/taskdefs/aspectjTaskdefs.properties"> <classpath> <pathelement location="${home.dir}/tools/aspectj/lib/aspectjtools.jar"/> </classpath> </taskdef> <target name="compile" > <iajc sourceroots="${home.dir}/ec/project/src" classpath="${home.dir}/tools/aspectj/lib/aspectjrt.jar"/> </target> </project>
Below is script with most everything in it. The compile process...
Runs in incremental mode, recompiling when the user hits return;
Reads all the source files from two directories;
Reads binary .class files from input jar and directory;
Uses a binary aspect library for persistence;
Outputs to an application jar; and
Copies resources from the source directories and binary input jar and directories to the application jar.
When this target is built, the compiler will build once and then wait for input from the user. Messages are printed as usual. When the user has quit, then this runs the application.
<target name="build-test" > <iajc outjar="${home.dir}/output/application.jar" sourceRootCopyFilter="**/CVS/*,**/*.java" inpathDirCopyFilter="**/CVS/*,**/*.java,**/*.class" incremental="true" > <sourceroots> <pathelement location="${home.dir}/ec/project/src"/> <pathelement location="${home.dir}/ec/project/testsrc"/> </sourceroots> <inpath> <pathelement location="${home.dir}/build/module.jar"/> <pathelement location="${home.dir}/build/binary-input"/> </inpath> <aspectpath> <pathelement location="${home.dir}/ec/int/persist.jar"/> </aspectpath> <classpath> <pathelement location="${home.dir}/tools/aspectj/lib/aspectjrt.jar"/> </classpath> </iajc> <java classname="org.smart.app.Main"> <classpath> <pathelement location="${home.dir}/tools/aspectj/lib/aspectjrt.jar"/> <pathelement location="${home.dir}/ec/int/persist.jar"/> <pathelement location="${home.dir}/output/application.jar"/> </classpath> </java> </target>
For an example of a build script, see ../examples/build.xml.
Unlike javac, the ajc compiler always processes all input because new aspects can apply to updated classes and vice-versa. However, in the case where no files have been updated, there is no reason to recompile sources. One way to implement that is with an explicit dependency check using the uptodate task:
<target name="check.aspects.jar"> <uptodate property="build.unnecessary" targetfile="${aspects.module-jar}" > <srcfiles dir="${src1}" includes="**/*.aj"/> <srcfiles dir="${src2}/" includes="**/*.aj"/> </uptodate> </target> <target name="compile.aspects" depends="prepare,check.aspects.jar" unless="build.unnecessary"> <iajc ...
When using this technique, be careful to verify that binary input jars are themselves up-to-date after they would have been modified by any build commands.
Users may specify a message holder to which the compiler will pass all messages as they are generated. This will override all of the normal message printing, but does not prevent the task from failing if exceptions were thrown or if failonerror is true and the compiler detected errors in the sources.
Handling messages programmatically could be useful when using the compiler to verify code. If aspects consist of declare [error|warning], then the compiler can act to detect invariants in the code being processed. For code to compare expected and actual messages, see the AspectJ testing module (which is not included in the binary distribution).
This CompilerAdapter can be used in javac task calls by setting the
build.compiler
property.
This enables users to to easily switch between the Javac and AspectJ
compilers. However, because there are differences in source file
handling between the Javac task and the ajc compiler, not all
Javac task invocations can be turned over to iajc. However, ajc can
compile anything that Javac can, so it should be possible for any
given compile job to restate the Javac task in a way that can be
handled by iajc/ajc.
To build using the adapter, put the
aspectjtools.jar
on the system/ant classpath (e.g., in
${ANT_HOME}/lib
)
and define the
build.compiler
property as the fully-qualified name of the class,
org.aspectj.tools.ant.taskdefs.Ajc11CompilerAdapter
.
The AspectJ compiler should run for any compile using the Javac task
(for options, see the Ant documentation for the Javac task).
For example, the call below passes all out-of-date source files in the
src/org/aspectj
subdirectories to the
ajc
command along with the destination directory:
-- command: cp aspectj1.1/lib/aspectjtools.jar ant/lib ant/bin/ant -Dbuild.compiler=org.aspectj.tools.ant.taskdefs.Ajc11CompilerAdapter ... -- task invocation in the build script: <javac srcdir="src" includes="org/aspectj/**/*.java" destdir="dest" />
To pass ajc-specific arguments, use a compilerarg entry.
-- command Ant -Dbuild.compiler=org.aspectj.tools.ant.taskdefs.Ajc11CompilerAdapter -- build script <property name="ajc" value="org.aspectj.tools.ant.taskdefs.Ajc11CompilerAdapter"/> <javac srcdir="src" includes="org/aspectj/**/*.java" destdir="dest" > <compilerarg compiler="${ajc}" line="-argfile src/args.lst"/> <javac/>
The Javac task does special handling of source files that
can interfere with ajc. It removes any files that are not out-of-date
with respect to the corresponding .class files. But ajc requires all
source files, since an aspect may affect a source file that is not out
of date. (For a solution to this, see the build.compiler.clean
property described below.) Conversely, developers sometimes specify a source directory
to javac, and let it search for files for types it cannot find.
AspectJ will not do this kind of searching under the source directory
(since the programmer needs to control which sources are affected).
(Don't confuse the source directory used by Javac with the source root
used by ajc; if you specify a source root to ajc, it will compile
any source file under that source root (without exception or filtering).)
To replace source dir searching in Javac, use an Ant filter to specify
the source files.
The adapter supports any ajc command-line option passed using compilerarg, as well as the following options available only in AjcTask. Find more details on the following options in AjcTask (iajc).
-Xmaxmem
:
set maximum memory for forking (also settable in javac).
-Xlistfileargs
:
list file arguments (also settable in javac).
-Xfailonerror
:
throw BuildException on compiler error (also settable in javac).
-Xmessageholderclass
:
specify fully-qualified name of class to use as the message holder.
-Xcopyinjars
:
copy resources from any input jars to output
(default behavior since 1.1.1)
-Xsourcerootcopyfilter {filter}
:
copy resources from source directories to output (minus files specified in filter)
-Xtagfile {file}
:
use file to control incremental compilation
-Xsrcdir {dir}
:
add to list of ajc source roots (all source files will be included).
Special considerations when using Javac and compilerarg:
The names above may differ slightly from what you might expect from AjcTask; use these forms when specifying compilerarg.
By default the adapter will mimic the Javac task's copying of resource
files by specifying
"**/CVS/*,**/*.java,**/*.aj"
for the sourceroot copy filter.
To change this behavior, supply your own value
(e.g., "**/*"
to copy nothing).
Warning - define the system property
build.compiler.clean
to compile all files,
when available.
Javac prunes the source file list of "up-to-date" source files
based on the timestamps of corresponding .class files,
and will not compile if no sources are out of date.
This is wrong for ajc which requires all the files for each compile
and which may refer indirectly to sources using argument files.
To work around this, set the global property
build.compiler.clean
.
This tells the compiler adapter to delete all .class files
in the destination directory and re-execute the javac
task so javac can recalculate the list of source files. e.g.,
Ant -Dbuild.compiler=org.aspectj.tools.ant.taskdefs.Ajc11CompilerAdapter -Dbuild.compiler.clean=anything ...
Caveats to consider when using this global
build.compiler.clean
property:
If javac believes there are no out-of-date source files, then the adapter is never called and cannot clean up, and the "compile" will appear to complete successfully though it did nothing.
Cleaning will makes stepwise build processes fail if they depend on the results of the prior compilation being in the same directory, since cleaning deletes all .class files.
This clean process only permits one compile process at a time for each destination directory because it tracks recursion by writing a tag file to the destination directory.
When running incrementally, the clean happens only before the initial compile.
This task handles the same arguments as those used by the AspectJ 1.0 task.
This should permit those with existing build scripts using the Ajc Ant
task to continue using the same scripts when compiling with 1.1.
This will list any use of options no longer supported in 1.1
(e.g., lenient, strict, workingdir, preprocess, usejavac
,...),
and does not provide access to the new features of AspectJ 1.1.
(Developers using AspectJ 1.1 only should upgrade their scripts
to use AjcTask instead. This will not work for AspectJ 1.2 or later.)
Most attributes and nested elements are optional.
The compiler requires that the same version of
aspectjrt.jar
be specified on the classpath, and that some sources be
be specified
(using one or more of
argfiles
and
srcdir
(with patterns)).
Boolean parameters default to false
unless otherwise stated.
Table 4.1. AjcTask (ajc) options for specifying sources
Attribute | Description |
---|---|
srcdir | The base directory of the java files. See |
destdir | The target directory for the output .class files |
includes | Comma-separated list of patterns of files that must be included. No files are included when omitted. |
includesfile | The path to a file containing include patterns. |
excludes | Comma-separated list of patterns of files that must be excluded. No files (except default excludes) are excluded when omitted. |
excludesfile | The path to a file containing exclude patterns. |
defaultexcludes |
If true, then default excludes are used.
Default excludes are used when omitted
(i.e., defaults to |
classpath, classpathref | The classpath to use, optionally given as a reference to a classpath Path element defined elsewhere. |
bootclasspath, bootclasspathref | The bootclasspath to use, optionally given as a reference to a bootclasspath Path element defined elsewhere. |
extdirs | Paths to directories containting installed extensions. |
debug | If true, emit debug info in the .class files. |
deprecation | If true, emit messages about use of deprecated API. |
verbose | Emit compiler status messages during the compile. |
version | Emit version information and quit. |
failonerror |
If true, throw BuildException to halt build if there
are any compiler errors.
If false, continue notwithstanding compile errors.
Defaults to |
source |
Value of -source option - ignored unless |
Table 4.2. Parameters ignored by the old ajc taskdef, but now supported or buggy
Attribute | Description | Supported? |
---|---|---|
encoding | Default encoding of source files. | yes |
optimize | Whether source should be compiled with optimization. | yes? |
target |
Generate class files for specific VM version, one of
[ | yes |
depend | Enables dependency-tracking. | no |
includeAntRuntime | Whether to include the Ant run-time libraries. | no |
includeJavaRuntime | Whether to include the run-time libraries from the executing VM. | no |
threads | Multi-threaded compilation | no |
The following table shows that many of the unique parameters in AspectJ 1.0 are no longer supported.
Table 4.3. Parameters unique to ajc
Attribute | Description | |
---|---|---|
X | deprecated X options include reweavable (on by default) reweavable:compress (compressed by default) | |
emacssym | Generate symbols for Emacs IDE support. | |
argfiles | A comma-delimited list of argfiles that contain a line-delimited list of source file paths (absolute or relative to the argfile). |
An argument file is a file (usually {file}.lst
)
containing a list of source file paths
(absolute or relative to the argfile).
You can use it to specify all source files to be compiled,
which ajc requires to avoid searching every possible source file
in the source path when building aspects.
If you specify an argfile to the ajc task, it will not include all
files in any specified source directory (which is the default
behavior for the Javac task when no includes are specified).
Conversely, if you specify excludes, they will be removed from
the list of files compiled even if they were specified
in an argument file.
The compiler also accepts arguments that are not source files, but the IDE support for such files varies, and Javac does not support them. Be sure to include exactly one argument on each line.
This task forms an implicit FileSet and supports all attributes of
<fileset>
(dir becomes srcdir) as well as
the nested
<include>
,
<exclude>
, and
<patternset>
elements.
These can be used to specify source files.
ajc
's
srcdir
,
classpath
,
bootclasspath
,
extdirs
, and
jvmarg
attributes are path-like structures and can also be set via nested
<src>
,
<classpath>
,
<bootclasspath>
,
<extdirs>
, and
<jvmargs>
elements, respectively.
Following is a declaration for the ajc task and a sample invocation
that uses the ajc compiler to compile the files listed in
default.lst
into the dest dir:
<project name="example" default="compile" > <taskdef name="ajc" classname="org.aspectj.tools.ant.taskdefs.Ajc10" > <!-- declare classes needed to run the tasks and tools --> <classpath> <pathelement location="${home.dir}/tools/aspectj/lib/aspectjtools.jar"/> </classpath> </taskdef> <target name="compile" > <mkdir dir="dest" /> <ajc destdir="dest" argfiles="default.lst" > <!-- declare classes needed to compile the target files --> <classpath> <pathelement location="${home.dir}/tools/aspectj/lib/aspectjrt.jar"/> </classpath> </ajc> </target> </project>
This build script snippet
<ajc srcdir="${src}" destdir="${build}" argfiles="demo.lst" />
compiles all .java files specified in the demo.lst and stores the .class files in the ${build} directory. Unlike the Javac task, the includes attribute is empty by default, so only those files specified in demo.lst are included.
This next example
<ajc srcdir="${src}" destdir="${build}" includes="spacewar/*,coordination/*" excludes="spacewar/Debug.java" />
compiles .java files under the ${src}
directory in the
spacewar and coordination packages, and stores the .class files in the
${build}
directory.
All source files under spacewar/ and coordination/ are used, except Debug.java.
See ../examples/build.xml for an example build script.
If you have problems with the tasks not solved by the documentation, please try to see if you have the same problems when running ajc directly on the command line.
If the problem occurs on the command line also, then the problem is not in the task. (It may be in the tools; please send bug reports.)
If the problem does not occur on the command line, then it may lie in the parameters you are supplying in Ant or in the task's handling of them.
If the build script looks correct and the problem only occurs when building from Ant, then please send a report (including your build file, if possible).
For the most up-to-date information on known problems, see the bug database for unresolved compiler bugs or taskdef bugs .
When running Ant build scripts under Eclipse 2.x variants, you will get a VerifyError because the Eclipse Ant support fails to isolate the Ant runtime properly. To run in this context, set up iajc to fork (and use forkclasspath). Eclipse 3.0 will fork Ant processes to avoid problems like this.
Memory and forking: Users email most often about the ajc task running out of memory. This is not a problem with the task; some compiles take a lot of memory, often more than similar compiles using javac.
Forking is now supported in both the Ajc11CompilerAdapter (javac) and AjcTask (iajc), and you can set the maximum memory available. You can also not fork and increase the memory available to Ant (see the Ant documentation, searching for ANT_OPTS, the variable they use in their scripts to pass VM options, e.g., ANT_OPTS=-Xmx128m).
For questions, you can send email to aspectj-users@dev.eclipse.org. (Do join the list to participate!) We also welcome any bug reports, patches, and features; you can submit them to the bug database at http://bugs.eclipse.org/bugs using the AspectJ product and Ant component.
Table of Contents
The AspectJ weaver takes class files as input and produces class files as output. The weaving process itself can take place at one of three different times: compile-time, post-compile time, and load-time. The class files produced by the weaving process (and hence the run-time behaviour of an application) are the same regardless of the approach chosen.
Compile-time weaving is the simplest approach. When you have the source code for an application, ajc will compile from source and produce woven class files as output. The invocation of the weaver is integral to the ajc compilation process. The aspects themselves may be in source or binary form. If the aspects are required for the affected classes to compile, then you must weave at compile-time. Aspects are required, e.g., when they add members to a class and other classes being compiled reference the added members.
Post-compile weaving (also sometimes called binary weaving) is used to weave existing class files and JAR files. As with compile-time weaving, the aspects used for weaving may be in source or binary form, and may themselves be woven by aspects.
Load-time weaving (LTW) is simply binary weaving defered until the point that a class loader loads a class file and defines the class to the JVM. To support this, one or more "weaving class loaders", either provided explicitly by the run-time environment or enabled through a "weaving agent" are required.
You may also hear the term "run-time weaving". We define this as the weaving of classes that have already been defined to the JVM (without reloading those classes). AspectJ 5 does not provide explicit support for run-time weaving although simple coding patterns can support dynamically enabling and disabling advice in aspects.
As of AspectJ 5 aspects (code style or annotation style) and woven classes are
reweavable by default. If you are developing AspectJ applications that are to be used
in a load-time weaving environment with an older version of the compiler you
need to specify the -Xreweavable
compiler option when building
them. This causes AspectJ to save additional state in the class files that is used
to support subsequent reweaving.
All load-time weaving is done in the context of a class loader, and hence the set of aspects used for weaving and the types that can be woven are affected by the class loader delegation model. This ensures that LTW complies with the Java 2 security model. The following rules govern the interaction of load-time weaving with class loading:
All aspects to be used for weaving must be defined to the weaver before any types to be woven are loaded. This avoids types being "missed" by aspects added later, with the result that invariants across types fail.
All aspects visible to the weaver are usable. A visible aspect is one defined by the weaving class loader or one of its parent class loaders. All concrete visible aspects are woven and all abstract visible aspects may be extended.
A class loader may only weave classes that it defines. It may not weave classes loaded by a delegate or parent class loader.
New in AspectJ 5 are a number of mechanisms to make load-time weaving easy to use. The load-time weaving mechanism is chosen through JVM startup options. Configuration files determine the set of aspects to be used for weaving and which types will be woven. Additional diagnostic options allow the user to debug the configuration and weaving process.
AspectJ 5 supports several ways of enabling load-time weaving for an application: agents, a command-line launch script, and a set of interfaces for integration of AspectJ load-time weaving in custom environments.
AspectJ 5 ships with a number of load-time weaving agents that enable load-time weaving. These agents and their configuration are execution environment dependent. Configuration for the supported environments is discussed later in this chapter.
Using Java 5 JVMTI you can specify the -javaagent:pathto/aspectjweaver.jar
option
to the JVM.
Using BEA JRockit and Java 1.3/1.4, the very same behavior can be obtained using BEA JRockit JMAPI features with
the -Xmanagement:class=org.aspectj.weaver.loadtime.JRockitAgent
aj
The aj command runs Java programs in Java 1.4 or
later by setting up WeavingURLClassLoader
as the
system class loader.
For more information, see aj.
The aj5 command runs Java programs in Java 5
by using the -javaagent:pathto/aspectjweaver.jar
option
described above.
For more information, see aj.
A public interface is provided to allow a user written class loader
to instantiate a weaver and weave classes after loading and before
defining them in the JVM. This enables load-time weaving to be supported in
environments where no weaving agent is available. It also allows the
user to explicitly restrict by class loader which classes can be woven.
For more information, see aj and the
API documentation and source for
WeavingURLClassLoader
and
WeavingAdapter
.
The weaver is configured using one or more META-INF/aop.xml
files located on the class loader search path. Each file may declare a list of
aspects to be used for weaving, type patterns describing which types
should woven, and a set of options to be passed to the weaver. In addition AspectJ 5
supports the definition of concrete aspects in XML. Aspects defined in this way
must extend an abstract aspect visible to the weaver. The abstract aspect
may define abstract pointcuts (but not abstract
methods). The following example shows a simple aop.xml file:
<aspectj> <aspects> <!-- declare two existing aspects to the weaver --> <aspect name="com.MyAspect"/> <aspect name="com.MyAspect.Inner"/> <!-- define a concrete aspect inline --> <concrete-aspect name="com.xyz.tracing.MyTracing" extends="tracing.AbstractTracing" precedence="com.xyz.first, *"> <pointcut name="tracingScope" expression="within(org.maw.*)"/> </concrete-aspect> <!-- Of the set of aspects declared to the weaver use aspects matching the type pattern "com..*" for weaving. --> <include within="com..*"/> <!-- Of the set of aspects declared to the weaver do not use any aspects with the @CoolAspect annotation for weaving --> <exclude within="@CoolAspect *"/> </aspects> <weaver options="-verbose"> <!-- Weave types that are within the javax.* or org.aspectj.* packages. Also weave all types in the foo package that do not have the @NoWeave annotation. --> <include within="javax.*"/> <include within="org.aspectj.*"/> <include within="(!@NoWeave foo.*) AND foo.*"/> <!-- Do not weave types within the "bar" pakage --> <exclude within="bar.*"/> <!-- Dump all types within the "com.foo.bar" package to the "./_ajdump" folder on disk (for diagnostic purposes) --> <dump within="com.foo.bar.*"/> <!-- Dump all types within the "com.foo.bar" package and sub-packages, both before are after they are woven, which can be used for byte-code generated at runtime <dump within="com.foo.bar..*" beforeandafter="true"/> </weaver> </aspectj>
The DTD defining the format of this file is available here: http://www.eclipse.org/aspectj/dtd/aspectj.dtd.
An aop.xml file contains two key sections: aspects
defines one
or more aspects to the weaver and controls which aspects are to be
used in the weaving process; weaver
defines weaver options and which
types should be woven.
The simplest way to define an aspect to the weaver is to
specify the fully-qualified name of the aspect type in an aspect element.
You can also
declare (and define to the weaver) aspects inline in the aop.xml file.
This is done using the concrete-aspect
element. A concrete-aspect
declaration must provide a pointcut definition for every abstract
pointcut in the abstract aspect it extends. This mechanism is a
useful way of externalizing configuration for infrastructure and
auxiliary aspects where the pointcut definitions themselves can be
considered part of the configuration of the service.
Refer to the next section for more details.
The aspects
element may optionally contain one or more include
and
exclude
elements (by default, all defined aspects are used for weaving).
Specifying include or exclude elements restricts the set of defined
aspects to be used for weaving to those that are matched by an include
pattern, but not by an exclude pattern. The within
attribute accepts
a type pattern of the same form as a within pcd, except that &&
and || are replaced by 'AND' and 'OR'.
Note that include
and exclude
elements affect all aspects
declared to the weaver including those in other aop.xml files. To help avoid unexpected
behaviour a lint warning is issued
if an aspect is not declared as a result of of applying these filters.
Also note aspect
and concrete-aspect
elements
must be used to declare aspects to the weaver i.e. include
and exclude
elements cannot be used find aspects on the class loader search path.
The weaver
element is used to pass options to the weaver and to specify
the set of types that should be woven. If no include elements are specified
then all types visible to the weaver will be woven. In addition the dump
element can be used capture on disk byte-code of woven classes for diagnostic purposes both before,
in the case of those generated at runtime, and after the weaving process.
When several configuration files are visible from a given weaving class loader
their contents are conceptually merged.
The files are merged in the order they are
found on the search path (with a regular getResourceAsStream
lookup)
according to the following rules:
The set of available aspects is the set of all
declared and defined aspects (aspect
and
concrete-aspect
elements of the aspects
section).
The set of aspects used for weaving is the subset of the available aspects that are matched by at least one include statement and are not matched by any exclude statements. If there are no include statements then all non-excluded aspects are included.
The set of types to be woven are those types matched by at
least one weaver include
element and not matched by any
weaver exclude
element. If there are no weaver include
statements then all non-excluded types are included.
The weaver options are derived by taking the union of the
options specified in each of the weaver options attribute specifications. Where an
option takes a value e.g. -warn:none
the most recently defined value
will be used.
It is not an error for the same aspect to be defined to the weaver in
more than one visible META-INF/aop.xml
file.
However, if the same concrete aspect
is defined in more than one aop.xml file then an error will be issued.
A concrete aspect
defined in this way will be used to weave types loaded by the
class loader that loaded the aop.xml file in which it was defined.
A META-INF/aop.xml
can be generated by
using either the -outxml
or -outxmlfile
options of the AspectJ compiler.
It will simply contain a (possibly empty) set of aspect elements; one for
each abstract or concrete aspect defined.
When used in conjuction with the -outjar
option
a JAR is produced that can be used
with the aj5 command or a load-time weaving environment.
It is possible to make an abstract aspect concrete by means of the META-INF/aop.xml
file. This is useful way to implement abstract pointcuts at deployment time, and also gives control
over precedence through the precedence
attribute of the
concrete-aspect
XML element.
Consider the following:
package mypack; @Aspect public abstract class AbstractAspect { // abstract pointcut: no expression is defined @Pointcut abstract void scope(); @Before("scope() && execution(* *..doSome(..))") public void before(JoinPoint jp) { .... } }
This aspect is equivalent to the following in code style:
package mypack; public abstract aspect AbstractAspect { // abstract pointcut: no expression is defined abstract pointcut scope(); before() : scope() && execution(* *..doSome(..)) { .... } }
This aspect (in either style) can be made concrete using META-INF/aop.xml
.
It defines the abstract pointcut scope()
. When using this mechanism the
following rules apply:
The parent aspect must be abstract. It can be an @AspectJ or a regular code style aspect.
Only a simple abstract pointcut can be implemented i.e. a pointcut that doesn't expose
state (through args(), this(), target(), if()
). In @AspectJ syntax
as illustrated in this sample, this means the method that hosts the pointcut must be abstract,
have no arguments, and return void.
The concrete aspect must implement all inherited abstract pointcuts.
The concrete aspect may not implement methods so the abstract aspect it extends may not contain any abstract methods.
A limitation of the implementation of this feature in AspectJ 1.5.0 is that aspects defined using aop.xml are not exposed to the weaver. This means that they are not affected by advice and ITDs defined in other aspects. Support for this capability will be considered in a future release.
If more complex aspect inheritance is required use regular aspect inheritance instead of XML. The following XML definition shows a valid concrete sub-aspect for the abstract aspects above:
<aspectj> <aspects> <concrete-aspect name="mypack.__My__AbstractAspect" extends="mypack.AbstractAspect"> <pointcut name="scope" expression="within(yourpackage..*)"/> </concrete-aspect> <aspects> </aspectj>
It is important to remember that the name
attribute in the
concrete-aspect
directive defines the fully qualified name that will be given to the
concrete aspect. It must a valid class name because the aspect will be generated on the fly by the weaver.
You must
also ensure that there are no name collisions. Note that the concrete aspect will be
defined at the classloader level for which the aop.xml is visible. This implies that if you need
to use the aspectof
methods to access the aspect instance(s) (depending on the perclause
of the aspect it extends) you have to use the helper API org.aspectj.lang.Aspects.aspectOf(..)
as in:
// exception handling omitted Class myConcreteAspectClass = Class.forName("mypack.__My__AbstractAspect"); // here we are using a singleton aspect AbstractAspect concreteInstance = Aspects.aspectOf(myConcreteAspectClass);
As described in the previous section, the concrete-aspect
element in
META-INF/aop.xml
gives the option to declare the precedence, just as
@DeclarePrecedence
or declare precedence
do in
aspect source code.
Sometimes it is necessary to declare precedence without extending any abstract aspect.
It is therefore possible to use the concrete-aspect
element without the extends
attribute and without any
pointcut
nested elements, just a precedence
attribute.
Consider the following:
<aspectj> <aspects> <concrete-aspect name="mypack.__MyDeclarePrecedence" precedence="*..*Security*, Logging+, *"/> </aspects> </aspectj>
This deployment time definitions is only declaring a precedence rule. You have to remember
that the name
attribute must be a valid fully qualified class name
that will be then reserved for this concrete-aspect and must not conflict with other classes
you deploy.
The table below lists the AspectJ options supported by LTW. All other options will be ignored and a warning issued.
Option | Purpose |
---|---|
-verbose
| Issue informational messages about the weaving process. Messages issued while the weaver is being
bootstrapped are accumulated until all options are parsed. If the messages are required to be output
immediately you can use the option -Daj.weaving.verbose=true on the JVM startup command line.
|
-debug
|
Issue a messages for each class passed to the weaver
indicating whether it was woven, excluded or ignored.
Also issue messages for classes
defined during the weaving process such as around advice
closures and concrete aspects defined in
META-INF/aop.xml .
|
-showWeaveInfo
|
Issue informational messages whenever the weaver touches a class file.
This option may also be enabled using the System property
-Dorg.aspectj.weaver.showWeaveInfo=true .
|
-Xlintfile:pathToAResource
| Configure lint messages as specified in the given resource (visible from this aop.xml file' classloader) |
-Xlint:default, -Xlint:ignore, ...
| Configure lint messages, refer to documentation for meaningfull values |
-nowarn, -warn:none
| Suppress warning messages |
-Xreweavable
| Produce class files that can subsequently be rewoven |
-XnoInline
| Don't inline around advice. |
-XmessageHandlerClass:...
| Provide alternative output destination to stdout/stderr for all weaver messages.
The given value must be the full qualified class name of a class that implements the
org.aspectj.bridge.IMessageHandler interface
and is visible to the classloader with which the weaver being configured is associated.
Exercise caution when packaging a custom message handler with an application that is to
be woven. The handler (as well as classes on which it depends) cannot itself be woven
by the aspects that are declared to the same weaver.
|
The following classes are not exposed to the LTW infrastructure regardless of
the aop.xml
file(s) used:
All org.aspectj.*
classes (and subpackages) - as those are needed by the infrastructure itself
All java.*
and javax.*
classes (and subpackages)
All sun.reflect.*
classes - as those are JDK specific classes used when reflective calls occurs
Despite these restrictions, it is perfectly possible to match call join points for calls to these types providing the calling class is exposed to the weaver. Subtypes of these excluded types that are exposed to the weaver may of course be woven.
Note that dynamic proxy representations are exposed to the LTW infrastructure and are not considered a special case.
Some lint options behave differently when used under load-time weaving. The adviceDidNotMatch
won't be handled as a warn (as during compile time) but as an info message.
To use LTW the aspectjweaver.jar
library must be added to the
classpath. This contains the AspectJ 5 runtime, weaver, weaving class loader and
weaving agents. It also contains the DTD for parsing XML weaving configuration files.
When using Java 5 the JVMTI agent can be used by starting the JVM with the following option (adapt according to the path to aspectjweaver.jar):
-javaagent:pathto/aspectjweaver.jar
Table of Contents
Systems, code, and build tools change over time, often not in step. Generally, later versions of the build tools understand earlier versions of the code, but systems should include versions of the runtime used to build the AspectJ program.
AspectJ programs can run on any Java VM of the required version. The AspectJ tools produce Java bytecode .class files that run on Java compatible VM's. If a Java class is changed by an aspect, the resulting class is binary compatible (as defined in the Java Language Specification). Further, the AspectJ compiler and weaving do all the exception checking required of Java compilers by the Java specifications.
Like other Java compilers,
the AspectJ compiler can target particular Java versions. Obviously, code
targeted at one version cannot be run in a VM of a lesser version. The
aspectjrt.jar
is designed to take advantage
of features available in Java 2 or Java 5, but will run in a JDK 1.1.x
environment, so you can use AspectJ to target older or restricted
versions of Java. However, there may be restricted variants of
JDK 1.1.x that do not have API's used by the AspectJ runtime. If
you deploy to one of those, you can email
aspectj-dev@eclipse.org
or download the runtime code to modify it for your environment.
Aside from the runtime, running the AspectJ tools themselves will require a more recent version of Java. You might use Java 5 to run the AspectJ compiler to produce code for Java 1.1.8.
When deploying AspectJ programs, include on the classpath the
classes, aspects, and the AspectJ runtime library
(aspectjrt.jar
). Use the version of the
runtime that came with the tools used to build the program. If the
runtime is earlier than the build tools used, it's very likely to
fail. If the runtime is later than the build tools used, it's possible
(but not guaranteed) that it will work.
Given that, three scenarios cause problems. First, you deploy new
aspects into an an existing system that already has aspects that were
built with a different version. Second, the runtime is already
deployed in your system and cannot be changed (e.g., some
application servers put aspectjrt.jar
on the
bootclasspath). Third, you (unintentionally) deploy two versions
of the runtime, and the one loaded by a parent loader is used).
In earlier versions of AspectJ, these problems present in obscure ways (e.g., unable to resolve a class). In later versions, a stack trace might even specify that the runtime version is out of sync with an aspect. To find out if the runtime you deployed is the one actually being used, log the defining class loader for the aspects and runtime.
Generally, binary aspects can be read by later versions of the weaver if the aspects were built by version 1.2.1 or later. (Some future weavers might have documented limitations in how far back they go.) If a post-1.2.1 weaver reads an aspect built by a later version, it will emit a message. If the weaver reads in a binary aspect and writes it out again, the result will be in the form produced by that weaver, not the original form of the aspect (just like other weaver output).
With unreleased or development versions of the tools, there are no guarantees for binary compatibility, unless they are stated in the release notes. If you use aspects built with development versions of the weaver, be careful to rebuild and redeploy with the next released version.
Generally, AspectJ source files can be read by later versions of the compiler. Language features do not change in dot releases (e.g., from 1.2.1 to 1.2.2). In some very rare cases, a language feature will no longer be supported or may change its meaning; these cases are documented in the release notes for that version. Some changes like this were necessary when moving to binary weaving in the 1.1 release, but at this time we don't anticipate more in the future. You might also find that the program behaves differently if you relied on behavior specific to that compiler/weaver, but which is not specified in the Semantics appendix to the Programming Guide.
Let's say your program behaves differently after being built with a new version of the AspectJ tools. It could be a bug that was introduced by the tools, but often it results from relying on behavior that was not guaranteed by the compiler. For example, the order of advice across two aspects is not guaranteed unless there is a precedence relationship between the aspects. If the program implicitly relies on a certain order that obtains in one compiler, it can fail when built with a different compiler.
Another trap is deploying into the same system, when the
aspectjrt.jar
has not been changed
accordingly.
Finally, when updating to a version that has new language features, there is a temptation to change both the code and the tools at the same time. It's best to validate the old code with the new tools before updating the code to use new features. That distinguishes problems of new engineering from those of new semantics.