ajc Man page

ajc General Commands Manual ajc


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 “” >.

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 file and @file
forms are equivalent, and are interpreted as meaning all the arguments
listed in the specified 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 ../progguide/implementa‐
tion.html) .

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.)

-injars JarList
deprecated: since 1.2, use -inpath, which also takes directo‐

-inpath Path
Accept as source bytecode any .class files in the The output
will include these classes, possibly as woven with any appli‐
cable aspects. Path is a single argument containing a list
of paths to zip files or directories, delimited by the plat‐
form-specific path delimiter.

-aspectpath 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 contain‐
ing a list of paths to jar files, delimited by the platform-
specific classpath delimiter.

-argfile 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 argu‐
ment files unlike the argument file is the only build speci‐
fication. The form @file is the same as specifying -argfile

-outjar output.jar
Put output classes in zip file output.jar.

-outxml Generate aop.xml file for load-time weaving with default

-outxmlfile custom/aop.xml
Generate aop.xml file for load-time weaving with custom name.

Run the compiler continuously. After the initial compila‐
tion, 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.

-sourceroots DirPaths
Find and build all .java or .aj source files under any direc‐
tory listed in DirPaths. DirPaths, like classpath, is a sin‐
gle 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

-emacssym Generate .ajesym symbol files for emacs support (deprecated).

-Xlint Same as -Xlint:warning (enabled by default)

Set default level for messages about potential programming
mistakes in crosscutting code. {level} may be ignore, warn‐
ing, or error. This overrides entries in
org/aspectj/weaver/XlintDefault.properties from aspectj‐
tools.jar, but does not override levels set using the -Xlint‐
file option.

-Xlintfile PropertyFile
Specify properties file to set levels for specific crosscut‐
ting 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 aspectj‐
tools.jar, which it also overrides.

-help Emit information on compiler options and usage

-version Emit the version of the AspectJ compiler

-classpath Path
Specify where to find user class files. Path is a single
argument containing a list of paths to zip files or directo‐
ries, delimited by the platform-specific path delimiter.

-bootclasspath Path
Override location of VM’s bootclasspath for purposes of eval‐
uating types when compiling. Path is a single argument con‐
taining a list of paths to zip files or directories, delim‐
ited by the platform-specific path delimiter.

-extdirs Path
Override location of VM’s extension directories for purposes
of evaluating types when compiling. Path is a single argu‐
ment containing a list of paths to directories, delimited by
the platform-specific path delimiter.

-d Directory
Specify where to place generated .class files. If not speci‐
fied, Directory defaults to the current working dir.

-target [1.1 to 1.5] Specify classfile target setting (1.1 to 1.5, default is 1.2)

-1.3 Set compliance level to 1.3 This implies -source 1.3 and
-target 1.1.

-1.4 Set compliance level to 1.4 (default) This implies -source
1.4 and -target 1.2.

-1.5 Set compliance level to 1.5. This implies -source 1.5 and
-target 1.5.

-source [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.

-nowarn Emit no warnings (equivalent to ‘-warn:none’) This does not
suppress messages generated by declare warning or Xlint.

-warn: 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

Same as -warn:deprecation

Emit no errors for unresolved imports

Keep compiling after error, dumping class files with problem

-g:[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.,

Preserve all local variables during code generation (to
facilitate debugging).

Compute reference information.

-encoding format
Specify default source encoding format. Specify custom
encoding on a per file basis by suffixing each input source
file/folder name with ‘[encoding]’.

-verbose Emit messages about accessed/processed compilation units

Emit messages about weaving

-log file Specify a log file for compiler messages.

-progress Show progress (requires -log mode).

-time Display speed information.

-noExit Do not call System.exit(n) at end of compilation (n=0 if no

-repeat N Repeat compilation process N times (typically to do perfor‐
mance 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.

-Xreweavable[:compress] (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

(Experimental) do not inline around advice

-XincrementalFile 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.

-Xajruntimelevel:1.2, ajruntimelevel:1.5
(Experimental) Allows code to be generated that targets a 1.2
or a 1.5 level AspectJ runtime (default 1.5)

File names
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 recom‐
mend 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 Specfication, Second
Edition (BOOK) http://java.sun.com/docs/books/jls/index.html and to
the The Java Virtual Machine Specification, Second Edition (BOOK)
http://java.sun.com/docs/books/vmspec/index.html 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 “” >.

A simple example

Compile two files:

ajc HelloWorld.java Trace.java

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:


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.

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 out‐
put, 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

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 emit‐
ted 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/exam‐
ples/tracing). This uses the following files:


Below, the path separator is taken as “;”, but file separators are “/”.
All commands are on one line. Adjust paths and commands to your envi‐
ronment 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 demonstra‐
tion’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 API
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, IMessage‐
Holder holder). ajc reports each message to the holder using IMessage‐
Holder.handleMessage(..). If you just want to collect the messages,
use MessageHandler as your IMessageHolder. For example, com‐
pile 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));

Stack Traces and the SourceFile attribute
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 Source‐
File attributes. In order to make sure all source file information is
available, the AspectJ compiler may in some cases encode multiple file‐
names 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

at Main.new$constructor_call37(Main.java;SynchAspect.java[1k]:1030)

where instead of the usual


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.