Examples of javassist.ClassPool

javassist.ClassPool
A container of CtClass objects. A CtClass object must be obtained from this object. If get() is called on this object, it searches various sources represented by ClassPath to find a class file and then it creates a CtClass object representing that class file. The created object is returned to the caller.
Memory consumption memo:
ClassPool objects hold all the CtClasses that have been created so that the consistency among modified classes can be guaranteed. Thus if a large number of CtClasses are processed, the ClassPool will consume a huge amount of memory. To avoid this, a ClassPool object should be recreated, for example, every hundred classes processed. Note that getDefault() is a singleton factory. Otherwise, detach() in CtClass should be used to avoid huge memory consumption.
ClassPool hierarchy:
ClassPools can make a parent-child hierarchy as java.lang.ClassLoaders. If a ClassPool has a parent pool, get() first asks the parent pool to find a class file. Only if the parent could not find the class file, get() searches the ClassPaths of the child ClassPool. This search order is reversed if ClassPath.childFirstLookup is true. @see javassist.CtClass @see javassist.ClassPath

      // Set up a different classloader to load a different version of the class
      String[] included = new String[]{CAR, CAR_EXT};
      ClassLoader tccl = Thread.currentThread().getContextClassLoader();
      ClassLoader cherryPickCl = new CherryPickClassLoader(included, null, tccl);
      Thread.currentThread().setContextClassLoader(cherryPickCl);
      ClassPool pool = ClassPool.getDefault();
      // Insert a classpath so that Maven does not complain about not finding the class
      pool.insertClassPath(new ClassClassPath(Car.class));
      CtClass carCt = pool.get(CAR);
      try {
         carCt.addField(CtField.make("public int year;", carCt));
         Class carClass = carCt.toClass();
         if (isNewExternalizer) {
            CtClass carExtCt = pool.get(CAR_EXT);
            CtMethod writeObjMeth = carExtCt.getMethod("writeObject",
                  "(Ljava/io/ObjectOutput;Ljava/lang/Object;)V");
            writeObjMeth.setBody("{\n" +
               "$1.writeObject(((" + CAR + ") $2).plateNumber);\n" +
               "$1.writeInt(((" + CAR + ") $2).year);\n" +

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      // Set up a different classloader to load a different version of the class
      String[] included = new String[]{PERSON, PERSON_EXT};
      ClassLoader tccl = Thread.currentThread().getContextClassLoader();
      ClassLoader cherryPickCl = new CherryPickClassLoader(included, null, tccl);
      Thread.currentThread().setContextClassLoader(cherryPickCl);
      ClassPool pool = ClassPool.getDefault();
      CtClass ct = pool.get(PERSON);
      try {
         ct.addField(CtField.make("public String name;", ct));
         Class clazz = ct.toClass();
         if (isNewExternalizer) {
            CtClass extCt = pool.get(PERSON_EXT);
            CtMethod writeObjMeth = extCt.getMethod("writeObject", "(Ljava/io/ObjectOutput;Ljava/lang/Object;)V");
            writeObjMeth.setBody("{\n" +
               "$1.writeInt(((" + PERSON + ") $2).age);\n" +
               "$1.writeObject((("  + PERSON + ") $2).name);\n" +
            "}\n"

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      // Set up a different classloader to load a different version of the class
      String[] included = new String[]{HOUSE, HOUSE_EXT};
      ClassLoader tccl = Thread.currentThread().getContextClassLoader();
      ClassLoader cherryPickCl = new CherryPickClassLoader(included, null, tccl);
      Thread.currentThread().setContextClassLoader(cherryPickCl);
      ClassPool pool = ClassPool.getDefault();
      CtClass ct = pool.get(HOUSE);
      try {
         ct.removeField(ct.getField("number"));
         Class clazz = ct.toClass();
         if (isNewExternalizer) {
            CtClass extCt = pool.get(HOUSE_EXT);
            CtMethod writeObjMeth = extCt.getMethod("writeObject", "(Ljava/io/ObjectOutput;Ljava/lang/Object;)V");
            writeObjMeth.setBody("{\n" +
               "$1.writeInt(0);\n" + // Safe the spot to avoid incompatibility
               "$1.writeObject((("  + HOUSE + ") $2).street);\n" +
            "}\n"

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        return connection.getLastModified();
    }


    private void createSynthComponentClass(String name) throws CannotCompileException, NotFoundException, IOException
    {
        ClassPool pool = new ClassPool();
        // Inside Maven Surefire, the system classpath is not sufficient to find all
        // the necessary files.
        pool.appendClassPath(new LoaderClassPath(extraLoader));


        CtClass ctClass = pool.makeClass(SYNTH_COMPONENT_CLASSNAME);


        ctClass.setSuperclass(pool.get(BasicComponent.class.getName()));


        // Implement method getName()


        CtMethod method = CtNewMethod.make("public String getName() { return \"" + name + "\"; }", ctClass);
        ctClass.addMethod(method);


        ctClass.addInterface(pool.get(Named.class.getName()));


        ctClass.writeFile(extraClasspath.getAbsolutePath());
    }

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    @Test
    public void reload_a_base_class() throws Exception
    {
        createImplementationClass(BASE_CLASS, "initial from base");


        ClassPool pool = new ClassPool(null);


        pool.appendSystemPath();
        pool.appendClassPath(classesDir.getAbsolutePath());


        CtClass ctClass = pool.makeClass(CLASS);


        ctClass.setSuperclass(pool.get(BASE_CLASS));


        ctClass.writeFile(classesDir.getAbsolutePath());


        Registry registry = createRegistry();

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    }


    private void createImplementationClass(String className, String status) throws NotFoundException,
            CannotCompileException, IOException
    {
        ClassPool pool = new ClassPool(null);


        pool.appendSystemPath();


        CtClass ctClass = pool.makeClass(className);


        ctClass.addInterface(pool.get(ReloadableService.class.getName()));


        CtMethod method = new CtMethod(pool.get("java.lang.String"), "getStatus", null, ctClass);


        method.setBody(String.format("return \"%s\";", status));


        ctClass.addMethod(method);

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        ctClass.writeFile(classesDir.getAbsolutePath());
    }


    private void createInvalidImplentationClass() throws Exception
    {
        ClassPool pool = new ClassPool(null);


        pool.appendSystemPath();


        CtClass ctClass = pool.makeClass(CLASS);


        ctClass.setModifiers(Modifier.ABSTRACT | Modifier.PUBLIC);
        ctClass.addInterface(pool.get(ReloadableService.class.getName()));


        CtConstructor constructor = new CtConstructor(new CtClass[0], ctClass);


        constructor.setBody("return $0;");

View Full Code Here

        InternalComponentResources resources = mockInternalComponentResources();


        String componentClassName = StateHolder.class.getName();
        Class asoClass = ReadOnlyBean.class;


        ClassPool pool = new ClassPool();
        ClassLoader contextLoader = Thread.currentThread().getContextClassLoader();
        pool.appendClassPath(new LoaderClassPath(contextLoader));


        Loader loader = new Loader(contextLoader, pool);


        loader.delegateLoadingOf("org.apache.tapestry.");


        CtClass ctClass = pool.get(componentClassName);
        InternalClassTransformation transformation = new InternalClassTransformationImpl(ctClass,
                _contextClassLoader, log, null);


        replay();


        new ApplicationStateWorker(manager).transform(transformation, model);


        verify();


        transformation.finish();


        Class transformedClass = pool.toClass(ctClass, loader);


        Instantiator instantiator = transformation.createInstantiator(transformedClass);


        Object component = instantiator.newInstance(resources);

View Full Code Here

    }


    private void createSynthComponentClass(String name) throws CannotCompileException,
            NotFoundException, IOException
    {
        ClassPool pool = new ClassPool();
        // Inside Maven Surefire, the system classpath is not sufficient to find all
        // the necessary files.
        pool.appendClassPath(new LoaderClassPath(_extraLoader));


        CtClass ctClass = pool.makeClass(SYNTH_COMPONENT_CLASSNAME);


        ctClass.setSuperclass(pool.get(BasicComponent.class.getName()));


        // Implement method getName()


        CtMethod method = CtNewMethod.make(
                "public String getName() { return \"" + name + "\"; }",
                ctClass);
        ctClass.addMethod(method);


        ctClass.addInterface(pool.get(Named.class.getName()));


        ctClass.writeFile(_extraClasspath.getAbsolutePath());
    }

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     * modifying one or more CtClass instances.
     */
    @BeforeMethod
    public void setup_classpool()
    {
        _classPool = new ClassPool();


        _loader = new Loader(_contextClassLoader, _classPool);


        // This ensures that only the classes we explicitly access and modify
        // are loaded by the new loader; everthing else comes out of the common

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