Package javassist

Class CtBehavior

  • Direct Known Subclasses:
    CtConstructor, CtMethod
    public abstract class CtBehavior
extends CtMember
    CtBehavior represents a method, a constructor, or a static constructor (class initializer). It is the abstract super class of CtMethod and CtConstructor.

    To directly read or modify bytecode, obtain MethodInfo objects.

    See Also:
    getMethodInfo()

    • Method Summary

      All Methods Instance Methods Abstract Methods Concrete Methods 
      Modifier and Type Method Description
      void addCatch​(java.lang.String src, CtClass exceptionType)
      Adds a catch clause that handles an exception thrown in the body.
      void addCatch​(java.lang.String src, CtClass exceptionType, java.lang.String exceptionName)
      Adds a catch clause that handles an exception thrown in the body.
      void addLocalVariable​(java.lang.String name, CtClass type)
      Declares a new local variable.
      void addParameter​(CtClass type)
      Appends a new parameter, which becomes the last parameter.
      java.lang.Object getAnnotation​(java.lang.Class<?> clz)
      Returns the annotation if the class has the specified annotation class.
      java.lang.Object[] getAnnotations()
      Returns the annotations associated with this method or constructor.
      byte[] getAttribute​(java.lang.String name)
      Obtains an attribute with the given name.
      java.lang.Object[] getAvailableAnnotations()
      Returns the annotations associated with this method or constructor.
      java.lang.Object[][] getAvailableParameterAnnotations()
      Returns the parameter annotations associated with this method or constructor.
      CtClass[] getExceptionTypes()
      Obtains exceptions that this method/constructor may throw.
      java.lang.String getGenericSignature()
      Returns the generic signature of the method.
      abstract java.lang.String getLongName()
      Returns the method or constructor name followed by parameter types such as javassist.CtBehavior.stBody(String).
      MethodInfo getMethodInfo()
      Returns the MethodInfo representing this method/constructor in the class file.
      MethodInfo getMethodInfo2()
      Returns the MethodInfo representing the method/constructor in the class file (read only).
      int getModifiers()
      Obtains the modifiers of the method/constructor.
      java.lang.Object[][] getParameterAnnotations()
      Returns the parameter annotations associated with this method or constructor.
      CtClass[] getParameterTypes()
      Obtains parameter types of this method/constructor.
      java.lang.String getSignature()
      Returns the method signature (the parameter types and the return type).
      boolean hasAnnotation​(java.lang.String typeName)
      Returns true if the class has the specified annotation type.
      void insertAfter​(java.lang.String src)
      Inserts bytecode at the end of the body.
      void insertAfter​(java.lang.String src, boolean asFinally)
      Inserts bytecode at the end of the body.
      void insertAfter​(java.lang.String src, boolean asFinally, boolean redundant)
      Inserts bytecode at the end of the body.
      int insertAt​(int lineNum, boolean modify, java.lang.String src)
      Inserts bytecode at the specified line in the body.
      int insertAt​(int lineNum, java.lang.String src)
      Inserts bytecode at the specified line in the body.
      void insertBefore​(java.lang.String src)
      Inserts bytecode at the beginning of the body.
      void insertParameter​(CtClass type)
      Inserts a new parameter, which becomes the first parameter.
      void instrument​(CodeConverter converter)
      Modifies the method/constructor body.
      void instrument​(ExprEditor editor)
      Modifies the method/constructor body.
      abstract boolean isEmpty()
      Returns true if the body is empty.
      void setAttribute​(java.lang.String name, byte[] data)
      Adds an attribute.
      void setBody​(java.lang.String src)
      Sets a method/constructor body.
      void setBody​(java.lang.String src, java.lang.String delegateObj, java.lang.String delegateMethod)
      Sets a method/constructor body.
      void setExceptionTypes​(CtClass[] types)
      Sets exceptions that this method/constructor may throw.
      void setGenericSignature​(java.lang.String sig)
      Set the generic signature of the method.
      void setModifiers​(int mod)
      Sets the encoded modifiers of the method/constructor.
      void useCflow​(java.lang.String name)
      Declares to use $cflow for this method/constructor.

      • Methods inherited from class java.lang.Object

        equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

    • Method Detail

      • getLongName

        public abstract java.lang.String getLongName()
        Returns the method or constructor name followed by parameter types such as javassist.CtBehavior.stBody(String).
        Since:
        3.5

      • getMethodInfo

        public MethodInfo getMethodInfo()
        Returns the MethodInfo representing this method/constructor in the class file.

        If you modify the bytecode through the returned MethodInfo object, you might have to explicitly rebuild a stack map table. Javassist does not automatically rebuild it for avoiding unnecessary rebuilding.

        See Also:
        MethodInfo.rebuildStackMap(ClassPool)

      • getMethodInfo2

        public MethodInfo getMethodInfo2()
        Returns the MethodInfo representing the method/constructor in the class file (read only). Normal applications do not need calling this method. Use getMethodInfo().

        The MethodInfo object obtained by this method is read only. Changes to this object might not be reflected on a class file generated by toBytecode(), toClass(), etc in CtClass.

        This method is available even if the CtClass containing this method is frozen. However, if the class is frozen, the MethodInfo might be also pruned.

        See Also:
        getMethodInfo(), CtClass.isFrozen(), CtClass.prune()

      • getModifiers

        public int getModifiers()
        Obtains the modifiers of the method/constructor.
        Specified by:
        getModifiers in class CtMember
        Returns:
        modifiers encoded with javassist.Modifier.
        See Also:
        Modifier

      • setModifiers

        public void setModifiers​(int mod)
        Sets the encoded modifiers of the method/constructor.

        Changing the modifiers may cause a problem. For example, if a non-static method is changed to static, the method will be rejected by the bytecode verifier.

        Specified by:
        setModifiers in class CtMember
        See Also:
        Modifier

      • hasAnnotation

        public boolean hasAnnotation​(java.lang.String typeName)
        Returns true if the class has the specified annotation type.
        Specified by:
        hasAnnotation in class CtMember
        Parameters:
        typeName - the name of annotation type.
        Returns:
        true if the annotation is found, otherwise false.
        Since:
        3.21

      • getAnnotation

        public java.lang.Object getAnnotation​(java.lang.Class<?> clz)
                               throws java.lang.ClassNotFoundException
        Returns the annotation if the class has the specified annotation class. For example, if an annotation @Author is associated with this method/constructor, an Author object is returned. The member values can be obtained by calling methods on the Author object.
        Specified by:
        getAnnotation in class CtMember
        Parameters:
        clz - the annotation class.
        Returns:
        the annotation if found, otherwise null.
        Throws:
        java.lang.ClassNotFoundException
        Since:
        3.11

      • getAnnotations

        public java.lang.Object[] getAnnotations()
                                  throws java.lang.ClassNotFoundException
        Returns the annotations associated with this method or constructor.
        Specified by:
        getAnnotations in class CtMember
        Returns:
        an array of annotation-type objects.
        Throws:
        java.lang.ClassNotFoundException
        Since:
        3.1
        See Also:
        getAvailableAnnotations()

      • getAvailableAnnotations

        public java.lang.Object[] getAvailableAnnotations()
        Returns the annotations associated with this method or constructor. If any annotations are not on the classpath, they are not included in the returned array.
        Specified by:
        getAvailableAnnotations in class CtMember
        Returns:
        an array of annotation-type objects.
        Since:
        3.3
        See Also:
        getAnnotations()

      • getParameterAnnotations

        public java.lang.Object[][] getParameterAnnotations()
                                             throws java.lang.ClassNotFoundException
        Returns the parameter annotations associated with this method or constructor.
        Returns:
        an array of annotation-type objects. The length of the returned array is equal to the number of the formal parameters. If each parameter has no annotation, the elements of the returned array are empty arrays.
        Throws:
        java.lang.ClassNotFoundException
        Since:
        3.1
        See Also:
        getAvailableParameterAnnotations(), getAnnotations()

      • getAvailableParameterAnnotations

        public java.lang.Object[][] getAvailableParameterAnnotations()
        Returns the parameter annotations associated with this method or constructor. If any annotations are not on the classpath, they are not included in the returned array.
        Returns:
        an array of annotation-type objects. The length of the returned array is equal to the number of the formal parameters. If each parameter has no annotation, the elements of the returned array are empty arrays.
        Since:
        3.3
        See Also:
        getParameterAnnotations(), getAvailableAnnotations()

      • getSignature

        public java.lang.String getSignature()
        Returns the method signature (the parameter types and the return type). The method signature is represented by a character string called method descriptor, which is defined in the JVM specification. If two methods/constructors have the same parameter types and the return type, getSignature() returns the same string (the return type of constructors is void).

        Note that the returned string is not the type signature contained in the SignatureAttirbute. It is a descriptor.

        Specified by:
        getSignature in class CtMember
        See Also:
        Descriptor, getGenericSignature()

      • getExceptionTypes

        public CtClass[] getExceptionTypes()
                            throws NotFoundException
        Obtains exceptions that this method/constructor may throw.
        Returns:
        a zero-length array if there is no throws clause.
        Throws:
        NotFoundException

      • isEmpty

        public abstract boolean isEmpty()
        Returns true if the body is empty.

      • setBody

        public void setBody​(java.lang.String src)
             throws CannotCompileException
        Sets a method/constructor body.
        Parameters:
        src - the source code representing the body. It must be a single statement or block. If it is null, the substituted body does nothing except returning zero or null.
        Throws:
        CannotCompileException

      • setBody

        public void setBody​(java.lang.String src,
                    java.lang.String delegateObj,
                    java.lang.String delegateMethod)
             throws CannotCompileException
        Sets a method/constructor body.
        Parameters:
        src - the source code representing the body. It must be a single statement or block. If it is null, the substituted body does nothing except returning zero or null.
        delegateObj - the source text specifying the object that is called on by $proceed().
        delegateMethod - the name of the method that is called by $proceed().
        Throws:
        CannotCompileException

      • getAttribute

        public byte[] getAttribute​(java.lang.String name)
        Obtains an attribute with the given name. If that attribute is not found in the class file, this method returns null.

        Note that an attribute is a data block specified by the class file format. It is not an annotation. See AttributeInfo.

        Specified by:
        getAttribute in class CtMember
        Parameters:
        name - attribute name

      • setAttribute

        public void setAttribute​(java.lang.String name,
                         byte[] data)
        Adds an attribute. The attribute is saved in the class file.

        Note that an attribute is a data block specified by the class file format. It is not an annotation. See AttributeInfo.

        Specified by:
        setAttribute in class CtMember
        Parameters:
        name - attribute name
        data - attribute value

      • useCflow

        public void useCflow​(java.lang.String name)
              throws CannotCompileException
        Declares to use $cflow for this method/constructor. If $cflow is used, the class files modified with Javassist requires a support class javassist.runtime.Cflow at runtime (other Javassist classes are not required at runtime).

        Every $cflow variable is given a unique name. For example, if the given name is "Point.paint", then the variable is indicated by $cflow(Point.paint).

        Parameters:
        name - $cflow name. It can include alphabets, numbers, _, $, and . (dot).
        Throws:
        CannotCompileException
        See Also:
        Cflow

      • addLocalVariable

        public void addLocalVariable​(java.lang.String name,
                             CtClass type)
                      throws CannotCompileException
        Declares a new local variable. The scope of this variable is the whole method body. The initial value of that variable is not set. The declared variable can be accessed in the code snippet inserted by insertBefore(), insertAfter(), etc.

        If the second parameter asFinally to insertAfter() is true, the declared local variable is not visible from the code inserted by insertAfter().

        Parameters:
        name - the name of the variable
        type - the type of the variable
        Throws:
        CannotCompileException
        See Also:
        insertBefore(String), insertAfter(String)

      • insertBefore

        public void insertBefore​(java.lang.String src)
                  throws CannotCompileException
        Inserts bytecode at the beginning of the body.

        If this object represents a constructor, the bytecode is inserted before a constructor in the super class or this class is called. Therefore, the inserted bytecode is subject to constraints described in Section 4.8.2 of The Java Virtual Machine Specification (2nd ed). For example, it cannot access instance fields or methods although it may assign a value to an instance field directly declared in this class. Accessing static fields and methods is allowed. Use insertBeforeBody() in CtConstructor.

        Parameters:
        src - the source code representing the inserted bytecode. It must be a single statement or block.
        Throws:
        CannotCompileException
        See Also:
        CtConstructor.insertBeforeBody(String)

      • insertAfter

        public void insertAfter​(java.lang.String src)
                 throws CannotCompileException
        Inserts bytecode at the end of the body. The bytecode is inserted just before every return instruction. It is not executed when an exception is thrown.
        Parameters:
        src - the source code representing the inserted bytecode. It must be a single statement or block.
        Throws:
        CannotCompileException

      • insertAfter

        public void insertAfter​(java.lang.String src,
                        boolean asFinally)
                 throws CannotCompileException
        Inserts bytecode at the end of the body. The bytecode is inserted just before every return instruction.
        Parameters:
        src - the source code representing the inserted bytecode. It must be a single statement or block.
        asFinally - true if the inserted bytecode is executed not only when the control normally returns but also when an exception is thrown. If this parameter is true, the inserted code cannot access local variables.
        Throws:
        CannotCompileException

      • insertAfter

        public void insertAfter​(java.lang.String src,
                        boolean asFinally,
                        boolean redundant)
                 throws CannotCompileException
        Inserts bytecode at the end of the body. The bytecode is inserted just before every return instruction.
        Parameters:
        src - the source code representing the inserted bytecode. It must be a single statement or block.
        asFinally - true if the inserted bytecode is executed not only when the control normally returns but also when an exception is thrown. If this parameter is true, the inserted code cannot access local variables.
        redundant - if true, redundant bytecode will be generated. the redundancy is necessary when some compilers (Kotlin?) generate the original bytecode. The other insertAfter methods calls this method with false for this parameter. A tip is to pass this.getDeclaringClass().isKotlin() to this parameter.
        Throws:
        CannotCompileException
        Since:
        3.26
        See Also:
        CtClass.isKotlin(), CtMember.getDeclaringClass()

      • addCatch

        public void addCatch​(java.lang.String src,
                     CtClass exceptionType)
              throws CannotCompileException
        Adds a catch clause that handles an exception thrown in the body. The catch clause must end with a return or throw statement.
        Parameters:
        src - the source code representing the catch clause. It must be a single statement or block.
        exceptionType - the type of the exception handled by the catch clause.
        Throws:
        CannotCompileException

      • addCatch

        public void addCatch​(java.lang.String src,
                     CtClass exceptionType,
                     java.lang.String exceptionName)
              throws CannotCompileException
        Adds a catch clause that handles an exception thrown in the body. The catch clause must end with a return or throw statement.
        Parameters:
        src - the source code representing the catch clause. It must be a single statement or block.
        exceptionType - the type of the exception handled by the catch clause.
        exceptionName - the name of the variable containing the caught exception, for example, $e.
        Throws:
        CannotCompileException

      • insertAt

        public int insertAt​(int lineNum,
                    java.lang.String src)
             throws CannotCompileException
        Inserts bytecode at the specified line in the body. It is equivalent to:
        insertAt(lineNum, true, src)
        See this method as well.
        Parameters:
        lineNum - the line number. The bytecode is inserted at the beginning of the code at the line specified by this line number.
        src - the source code representing the inserted bytecode. It must be a single statement or block.
        Returns:
        the line number at which the bytecode has been inserted.
        Throws:
        CannotCompileException
        See Also:
        insertAt(int,boolean,String)

      • insertAt

        public int insertAt​(int lineNum,
                    boolean modify,
                    java.lang.String src)
             throws CannotCompileException
        Inserts bytecode at the specified line in the body.

        If there is not a statement at the specified line, the bytecode might be inserted at the line including the first statement after that line specified. For example, if there is only a closing brace at that line, the bytecode would be inserted at another line below. To know exactly where the bytecode will be inserted, call with modify set to false.

        Parameters:
        lineNum - the line number. The bytecode is inserted at the beginning of the code at the line specified by this line number.
        modify - if false, this method does not insert the bytecode. It instead only returns the line number at which the bytecode would be inserted.
        src - the source code representing the inserted bytecode. It must be a single statement or block. If modify is false, the value of src can be null.
        Returns:
        the line number at which the bytecode has been inserted.
        Throws:
        CannotCompileException