org.hotswap.agent.javassist

Class CtBehavior

java.lang.Object

org.hotswap.agent.javassist.CtMember

org.hotswap.agent.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:

getMethodInfo()

Field Summary

Fields

Modifier and Type	Field and Description
protected MethodInfo	methodInfo

Fields inherited from class org.hotswap.agent.javassist.CtMember

declaringClass

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	CtBehavior(CtClass clazz, MethodInfo minfo)

Method Summary

Modifier and Type	Method and Description
void	addCatch(String src, CtClass exceptionType) Adds a catch clause that handles an exception thrown in the body.
void	addCatch(String src, CtClass exceptionType, String exceptionName) Adds a catch clause that handles an exception thrown in the body.
void	addLocalVariable(String name, CtClass type) Declares a new local variable.
void	addParameter(CtClass type) Appends a new parameter, which becomes the last parameter.
protected void	extendToString(StringBuffer buffer) Invoked by CtMember.toString() to add to the buffer and provide the complete value.
Object	getAnnotation(Class clz) Returns the annotation if the class has the specified annotation class.
Object[]	getAnnotations() Returns the annotations associated with this method or constructor.
byte[]	getAttribute(String name) Obtains an attribute with the given name.
Object[]	getAvailableAnnotations() Returns the annotations associated with this method or constructor.
Object[][]	getAvailableParameterAnnotations() Returns the parameter annotations associated with this method or constructor.
CtClass[]	getExceptionTypes() Obtains exceptions that this method/constructor may throw.
String	getGenericSignature() Returns the generic signature of the method.
abstract 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.
Object[][]	getParameterAnnotations() Returns the parameter annotations associated with this method or constructor.
CtClass[]	getParameterTypes() Obtains parameter types of this method/constructor.
String	getSignature() Returns the method signature (the parameter types and the return type).
boolean	hasAnnotation(String typeName) Returns true if the class has the specified annotation type.
void	insertAfter(String src) Inserts bytecode at the end of the body.
void	insertAfter(String src, boolean asFinally) Inserts bytecode at the end of the body.
int	insertAt(int lineNum, boolean modify, String src) Inserts bytecode at the specified line in the body.
int	insertAt(int lineNum, String src) Inserts bytecode at the specified line in the body.
void	insertBefore(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(String name, byte[] data) Adds an attribute.
void	setBody(String src) Sets a method/constructor body.
void	setBody(String src, String delegateObj, String delegateMethod) Sets a method/constructor body.
void	setExceptionTypes(CtClass[] types) Sets exceptions that this method/constructor may throw.
void	setGenericSignature(String sig) Set the generic signature of the method.
void	setModifiers(int mod) Sets the encoded modifiers of the method/constructor.
void	useCflow(String name) Declares to use $cflow for this method/constructor.

Methods inherited from class org.hotswap.agent.javassist.CtMember

getDeclaringClass, getName, hasAnnotation, toString, visibleFrom

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

methodInfo

protected MethodInfo methodInfo

Constructor Detail

CtBehavior

protected CtBehavior(CtClass clazz,
                     MethodInfo minfo)

Method Detail

extendToString

protected void extendToString(StringBuffer buffer)

Description copied from class: CtMember

Invoked by CtMember.toString() to add to the buffer and provide the complete value. Subclasses should invoke this method, adding a space before each token. The modifiers for the member are provided first; subclasses should provide additional data such as return type, field or method name, etc.

Specified by:

extendToString in class CtMember

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:

javassist.bytecode.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(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()

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:

getAnnotations()

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(), getAnnotations()

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:

getParameterAnnotations(), getAvailableAnnotations()

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:

javassist.bytecode.Descriptor, getGenericSignature()

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:

SignatureAttribute.toMethodSignature(String)

setGenericSignature

public void setGenericSignature(String sig)

Set the generic signature of the method. It represents parameter types including type variables. See javassist.CtClass#setGenericSignature(String) for a code sample.

Specified by:

setGenericSignature in class CtMember

Parameters:

sig - a new generic signature.

Since:

3.17

See Also:

javassist.bytecode.SignatureAttribute.MethodSignature#encode()

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 javassist.bytecode.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 javassist.bytecode.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:

javassist.runtime.Cflow

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:

insertBefore(String), insertAfter(String)

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:

javassist.expr.Expr#replace(String), insertBefore(String)

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:

CtConstructor.insertBeforeBody(String)

insertAfter

public void insertAfter(String src)
                 throws CannotCompileException

Inserts bytecode at the end of the body. The bytecode is inserted just before every return insturction. 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 insturction.

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

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(int,boolean,String)

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