ajc
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# ajc

## Name

ajc — compiler and bytecode weaver for the AspectJ and Java languages

## Synopsis

`ajc` [`Options`] [`file...` | @`file...` | -argfile `file...`]

## Description

The ajc command compiles AspectJ and Java language files, weaving aspects as necessary to produce .class files compliant with any Java VM (1.1 or later). To do bytecode weaving, it also accepts input classes or aspects in binary form.

The arguments after the options specify the source file(s) to compile. (Specify source classes using the `-injars` or `-inpath` options, below.) Files may be listed directly on the command line, or listed in a file. The `-argfile `file`` and `@`file`` forms are equivalent, and are interpreted as meaning all the files listed in the specified file. Each line in these files should contain one option or filename. Comments, as in Java, start with `//` and extend to the end of the line.

NB: You must explicitly pass ajc all sources necessary for the compilation. When compiling source files containing aspects or pointcuts, be sure to include the source files for any types affected by the aspects or picked out by the pointcuts. (To exclude types from the scope affected by the aspect, change the corresponding pointcut or declaration.) This is necessary because, unlike javac, ajc does not search the sourcepath for classes. You may use the `-sourceroots` option to specify as source all the .aj and .java files in a set of directory trees.

### Options

-injars `JarList`

  deprecated: since 1.2, use -inpath, which also takes directories.

-inpath `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.

-aspectpath `JarList`

  Weave binary aspects from JarList zip files into all sources. The aspects should have been output by the same version of the compiler. To run the output classes requires putting all the aspectpath entries on the run classpath. JarList, like classpath, is a single argument containing a list of paths to jar files, delimited by the platform- specific classpath delimiter.

-argfile `File`

  The file is a line-delimited list of arguments. These arguments are inserted into the argument list.

-outjar `output.jar`

  Put output classes in zip file output.jar.

-incremental

  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.

-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.

-emacssym

  Generate .ajesym symbol files for emacs support

-Xlint

  Same as -Xlint:warning (enabled by default)

-Xlint:{level}

  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.

-Xlintfile `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.

-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 directories, delimited by the platform-specific path delimiter.

-bootclasspath `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.

-extdirs `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.

-d `Directory`

  Specify where to place generated .class files. If not specified, `Directory` defaults to the current working dir.

-target `[1.1 to 1.4]`

  Specify classfile target setting (1.1 to 1.4, default is 1.2)

-1.3

  Set compliance level to 1.3

-1.4

  Set compliance level to 1.4 (default)

-source `[1.3|1.4]`

  Toggle assertions (1.3 or 1.4, default is 1.3). 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.

-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 `Xlint`.
-deprecation

  Same as -warn:deprecation

-noImportError

  Emit no errors for unresolved imports

-proceedOnError

  Keep compiling after error, dumping class files with problem methods

-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.,
                     -g:lines,source

-preserveAllLocals

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

-referenceInfo

  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

-showWeaveInfo

  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 error)

-repeat `N`

  Repeat compilation process N times (typically to do performance analysis).

-Xnoweave

  (Experimental) produce unwoven class files for input using -injars.

-Xreweavable[:compress]

  (Experimental) 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.

-XnoInline

  (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.

-XserializableAspects

  (Experimental) Normally it is an error to declare aspects Serializable. This option removes that restriction.

### 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 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.

### Compatibility

AspectJ is a compatible extension to the Java programming language. The AspectJ compiler adheres to the The Java Language Specfication, 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.

### Examples

Example 1. A simple example

Compile two files:

            ajc HelloWorld.java Trace.java

Example 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 3. An example using -injars and -aspectpath

Bytecode weaving using -injars: AspectJ 1.1 supports weaving from input zip or jar files containing class files. 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 -injars will be woven into like other .class files, but they will specify any crosscutting code (i.e., they will not be woven into other types). To use aspects in their binary form to specify crosscutting, see -aspectpath below.

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 -injars 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, IMessageHolder holder)`.

### 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 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.

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