Examples of javassist.expr.ExprEditor

javassist.expr.ExprEditor
A translator of method bodies.
The users can define a subclass of this class to customize how to modify a method body. The overall architecture is similar to the strategy pattern.
If instrument() is called in CtMethod, the method body is scanned from the beginning to the end. Whenever an expression, such as a method call and a new expression (object creation), is found, edit() is called in ExprEdit. edit() can inspect and modify the given expression. The modification is reflected on the original method body. If edit() does nothing, the original method body is not changed.
The following code is an example:
This code inspects all method calls appearing in the method represented by cm and it prints the names and the line numbers of the methods declared in class Point. This code does not modify the body of the method represented by cm. If the method body must be modified, call replace() in MethodCall. @see javassist.CtClass#instrument(ExprEditor) @see javassist.CtMethod#instrument(ExprEditor) @see javassist.CtConstructor#instrument(ExprEditor) @see MethodCall @see NewExpr @see FieldAccess @see javassist.CodeConverter

  public void threadLocalBoolean(CtClass ctClass, Map<String, String> attributes) throws CannotCompileException {
    final String field = attributes.get("field");
    final String threadLocalField = attributes.get("threadLocalField");
    final IntHolder done = new IntHolder();
    for (CtConstructor ctConstructor : ctClass.getDeclaredConstructors()) {
      ctConstructor.instrument(new ExprEditor() {
        @Override
        public void edit(FieldAccess e) throws CannotCompileException {
          if (e.getFieldName().equals(field)) {
            if (e.isWriter()) {
              e.replace("{ }");
              done.value++;
            }
          }
        }
      });
    }
    ctClass.instrument(new ExprEditor() {
      @Override
      public void edit(FieldAccess e) throws CannotCompileException {
        if (e.getFieldName().equals(field)) {
          if (e.isReader()) {
            e.replace("{ $_ = ((Boolean) " + threadLocalField + ".get()).booleanValue(); }");

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    final String className = className_;
    final String field = attributes.get("field");
    final int index = Integer.valueOf(index_);
    final IntHolder replaced = new IntHolder();


    ctBehavior.instrument(new ExprEditor() {
      private int currentIndex = 0;


      @Override
      public void edit(MethodCall methodCall) throws CannotCompileException {
        if ((className == null || methodCall.getClassName().equals(className)) && (method.isEmpty() || methodCall.getMethodName().equals(method)) && (index == -1 || currentIndex++ == index)) {

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    if (!contains) {
      ctMethod.setName(newName);
      return;
    }
    final String methodName = ctMethod.getName();
    ctMethod.instrument(new ExprEditor() {
      @Override
      public void edit(MethodCall methodCall) throws CannotCompileException {
        if (methodName.equals(methodCall.getMethodName()) && superClassNames.contains(methodCall.getClassName())) {
          methodCall.replace("$_ = super." + newName + "($$);");
        }

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    final String className = className_;
    final String field = attributes.get("field");
    final int index = Integer.valueOf(index_);
    final IntHolder replaced = new IntHolder();


    ctBehavior.instrument(new ExprEditor() {
      private int currentIndex = 0;


      @Override
      public void edit(MethodCall methodCall) throws CannotCompileException {
        if ((className == null || methodCall.getClassName().equals(className)) && (method.isEmpty() || methodCall.getMethodName().equals(method)) && (index == -1 || currentIndex++ == index)) {

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  public static void findUnusedFields(CtClass ctClass) {
    final Set<String> readFields = new HashSet<String>();
    final Set<String> writtenFields = new HashSet<String>();
    try {
      ctClass.instrument(new ExprEditor() {
        @Override
        public void edit(FieldAccess fieldAccess) {
          if (fieldAccess.isReader()) {
            readFields.add(fieldAccess.getFieldName());
          } else if (fieldAccess.isWriter()) {

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  {
    // index method calls
    final BehaviorEntry behaviorEntry = BehaviorEntryFactory.create( behavior );
    try
    {
      behavior.instrument( new ExprEditor( )
      {
        @Override
        public void edit( MethodCall call )
        {
          String className = Descriptor.toJvmName( call.getClassName() );

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    // get all the called methods
    final List<MethodCall> methodCalls = Lists.newArrayList();
    try
    {
      method.instrument( new ExprEditor( )
      {
        @Override
        public void edit( MethodCall call )
        {
          methodCalls.add( call );

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    // collect all the field accesses, constructor calls, and method calls
    final List<FieldAccess> illegalFieldWrites = Lists.newArrayList();
    final List<ConstructorCall> constructorCalls = Lists.newArrayList();
    try
    {
      constructor.instrument( new ExprEditor( )
      {
        @Override
        public void edit( FieldAccess fieldAccess )
        {
          if( fieldAccess.isWriter() && constructorCalls.isEmpty() )

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          break;
        }
      }
      
      // update hash with method and field accesses
      behavior.instrument( new ExprEditor( )
      {
        @Override
        public void edit( MethodCall call )
        {
          updateHashWithString( digest, scrubClassName( call.getClassName() ) );

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