Package javassist

Class CtBehavior

java.lang.Object
javassist.CtMember
javassist.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:

  • Method Details

    • getLongName

      public abstract 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:

    • 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:

    • 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:

    • 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:

    • hasAnnotation

      public boolean hasAnnotation(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 Object getAnnotation(Class<?> clz) throws 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:
      ClassNotFoundException
      Since:
      3.11

    • getAnnotations

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

    • getAvailableAnnotations

      public 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:

    • getParameterAnnotations

      public Object[][] getParameterAnnotations() throws 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:
      ClassNotFoundException
      Since:
      3.1
      See Also:

    • getAvailableParameterAnnotations

      public 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:

    • getParameterTypes

      public CtClass[] getParameterTypes() throws NotFoundException
      Obtains parameter types of this method/constructor.
      Throws:
      NotFoundException

    • getSignature

      public 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:

    • getGenericSignature

      public String getGenericSignature()
      Returns the generic signature of the method. It represents parameter types including type variables.
      Specified by:
      getGenericSignature in class CtMember
      Since:
      3.17
      See Also:

    • setGenericSignature

      public void setGenericSignature(String sig)
      Set the generic signature of the method. It represents parameter types including type variables. See CtClass.setGenericSignature(String) for a code sample.
      Specified by:
      setGenericSignature in class CtMember
      Parameters:
      sig - a new generic signature.
      Since:
      3.17
      See Also:

    • 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

    • setExceptionTypes

      public void setExceptionTypes(CtClass[] types) throws NotFoundException
      Sets exceptions that this method/constructor may throw.
      Throws:
      NotFoundException

    • isEmpty

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

    • setBody

      public void setBody(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(String src, String delegateObj, 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(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(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(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:

    • addLocalVariable

      public void addLocalVariable(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:

    • insertParameter

      public void insertParameter(CtClass type) throws CannotCompileException
      Inserts a new parameter, which becomes the first parameter.
      Throws:
      CannotCompileException

    • addParameter

      public void addParameter(CtClass type) throws CannotCompileException
      Appends a new parameter, which becomes the last parameter.
      Throws:
      CannotCompileException

    • instrument

      public void instrument(CodeConverter converter) throws CannotCompileException
      Modifies the method/constructor body.
      Parameters:
      converter - specifies how to modify.
      Throws:
      CannotCompileException

    • instrument

      public void instrument(ExprEditor editor) throws CannotCompileException
      Modifies the method/constructor body.

      While executing this method, only replace() in Expr is available for bytecode modification. Other methods such as insertBefore() may collapse the bytecode because the ExprEditor loses its current position.

      Parameters:
      editor - specifies how to modify.
      Throws:
      CannotCompileException
      See Also:

    • insertBefore

      public void insertBefore(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:

    • insertAfter

      public void insertAfter(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(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(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:

    • addCatch

      public void addCatch(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(String src, CtClass exceptionType, 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, 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

      public int insertAt(int lineNum, boolean modify, 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