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JCop Manual

Command Line Tools

In the following we describe the usage of the JCop language compiler that is able to compile programs of the JCop and Java programming language. The compiler implements the language as defined in the JCop language specification version 1.0. The language definition has continuously been revised to precisely specify the language including various corner cases and combinations of features. The compiler is an extension to the JastAddJ Java compiler that is implemented based on the JastAdd compiler framework.



jcopc [Options] [file]


The jcopc command compiles JCop and Java source, producing .class files compliant with any Java VM (1.1 or later). The argument after the options specifies the source file to compile. Source files are specified by their full qualified name (package name + type name), separated by a dot (".") (rather than a folder delimiter as for javac).


-classpath <path>

Specify where to find user class files and annotation processors.

-sourcepath <path>

Specify where to find input source files. Only required if the sources aren’t located in the working directory.

jcopc  -sourcepath  src  myPckg.MyMainClass 

-d <directory>

Specify where to place generated class files.

jcopc  -d  bin  -sourcepath  src  myPckg.MyMainClass 

-sourcedump <path>

Dumps Java source files of the compiled classes into the specified folder.

jcopc  -sourcedump  dump  myPckg.MyMainClass 

-agg <path>

Generates a file containing an AGG graph representation of the program’s AST.

jcopc  -agg  output/agg  myPckg.MyMainClass 


Output JCop specific messages about what the compiler is doing.

jcopc  -ctl  myPckg.MyMainClass 
>  copying
>  to  src\jcop\lang
>  ..done
>  compiling:...src\de\uni_potsdam\hpi\swa\Widget.jcop  ..done
>  compiling:jcop\lang\  ..done
>  ..done
>  compile  and  weave  auxilliary  aspect    bin\jcop\lang\JCopAspect.aj
>  ..done
>  compiled  in  3723  millis


Loggs layer activation and composition information at runtime.

jcopc  -rtl  myPckg.MyMainClass
>  INFO:  accessing  base  method  of  getBMI
>  INFO:  accessing  method  getBMI  of  layer  Visualization


Output messages about what the compiler is doing


Print a synopsis of standard options


Output messages about aspect weaving


Print version information.

-xml-outline-path <path>

Generate an outline in XML format (useful for development environments)


Generate an outline in XML format (useful for development environments)

File Names

jcopc accepts source files with either the .java extension or the .jcop extension.

Underlying Java Command

If you encounter any problems using jcopc, you may use the plain Java command. For instance, the command

 jcopc -classpath bin -ctl MyApplication

is equivalent to

 java -jar -ea "%JCOP_HOME%\jcop.jar" -classpath bin -ctl MyApplication



jcop [Options] class [ argument ]


The jcop command launches a JCop or Java application. It does this by starting a Java runtime environment (instrumented with the AspectJ weaver), loading a specified class, and invoking that class's main method. The method declaration must look like a plain Java main method:

public static void main(String args[]) {...}

The method must be declared public and static, it must not return any value, and it must accept a String array as a parameter. By default, the first non-option argument is the name of the class to be invoked. A fully-qualified class name should be used.

The argument after the options specifies the class file to compile and by its full qualified name (package name + type name), separated by a dot (".").


As options all standard Java options are allowed.
If more than one classpath is specified, the entire classpath value must be quotet.

Specifying one classpath:

  jcop -classpath bin Main

Specifying several classpaths:

  jcop -classpath "bin;lib\MyJar.jar" Main

File Names

jcop accepts Java bytecode files with the class extension.

File Names

jcopc accepts source files with either the .java extension or the .jcop extension.

Underlying Java Command

If you encounter any problems using jcop, you may use the plain javacommand. For instance, the command

 jcop -classpath "bin;lib\mylib\" MyApplication

is equivalent to

 java -classpath "%JCOP_HOME%\aspectjweaver.jar;bin;lib\mylib\" "-Djava.system.class.loader=org.aspectj.weaver.loadtime.WeavingURLClassLoader" "-Daj.class.path=%ASPECTPATH%;%CLASSPATH%"   "-Daj.aspect.path=%ASPECTPATH%" MyApplication

Compiler API

The compiler can be executed programatically by invoking the compile method of jcop.compiler.JCopCompiler in the jcop.jar archive. All compiler arguments — including the name of the class to be compiled — must be passed to the String[] argument of this compile method. Note that key-value pairs are to separate elements of this string array. For example, the following command...

jcopc  -sourcepath  D:\example\src  -d  D:\example\bin  MyClass

... can be executed calling:

String[]  args  =
  new  String[]  {"-sourcepath",  "D:\example\src",  "-d",  "D:\example\bin",  "MyClass"};

Restrictions and Limitations

Restrictions to Plain Java Programs

In general, JCop is a superset of Java, thus any Java programs should be compilable and executable using JCop. However, the following limitations need to be considered for plain Java source code.

Primitives and Boxing in Java 5

The underlying JastAddJ compiler is not able to perform type boxing in combination with generics. The following listing describes such an scenario.

Vector<Byte>  bytecode  =  new  Vector<Byte>();
for(byte  bc  :  bytecode)  //  this  will  compile  but  not  run

The above code will compile, however, launching will cause a bytecode verification error similar to the following:

Exception  in  thread  "main"  java.lang.VerifyError:
(class:  Test,  method:  <init>  signature:  ()V)
Register  2  contains  wrong  type
Could  not  find  the  main  class:  Test.    Program  will  exit.

As a workaround, we suggest to consistently use class types instead of primitives in such cases.

Vector<Byte>  bytecode  =  new  Vector<Byte>();for(Byte  bc  :  bytecode)

Reserved Keywords

In addition to Java’s keywords, the following keywords are introduced by JCop and cannot be used as identifiers. This might require identifier renaming in existing Java programs.

after, before, call, context, layer, on, proceed, subject, with, without, when, ".."

Limitations of the JCop Compiler

Default Package

Layer declarations in classes of the default package are not supported, thus those classes must contain a package declaration. However, layer import and (de-)activation statements can be used in the default package.

Nested Class Support

Layers cannot be declared and activated within nested and anonymous classes, yet.

public  class  MyClass  {
  class  MyInnerClass  {
    void  m()  {  ...  }
    layer  MyLayer{  ...  }  //  this  won’t  work
  void  myMethod()  {
    new  MyNestedClass()  {
    layer  MyLayer  {  ...  }  //  this  won’t  work

Context Object Methods

Due to implementation details, context objects must not contain methods of the folloing signature:

  • void initLayers()
  • boolean isActiveFor(String)
  • String jcop_name()

jcop accepts Java bytecode files with the class extension.