Java Doc for CtNewMethod.java in  » Byte-Code » Javassist » javassist » Java Source Code / Java DocumentationJava Source Code and Java Documentation

"public Object id(Object obj) { return obj; }"

"public Object id(Object obj) { return obj; }"

If the source code includes $proceed(), then it is compiled into a method call on the specified object.
Parameters:
  src - the source text.

The following method is an example of the created method.

int f(int p, int q) {
 return super.f(p, q);
 }

The name of the created method can be changed by setName().
Parameters:
  delegate - the method that the created method forwards to.
Parameters:
  declaring - the class to which the created method isadded.

"public Object id(Object obj) { return obj; }"

"public Object id(Object obj) { return obj; }"

If the source code includes $proceed(), then it is compiled into a method call on the specified object.
Parameters:
  src - the source text.
Parameters:
  declaring - the class to which the created method is added.
Parameters:
  delegateObj - the source text specifying the objectthat is called on by $proceed().
Parameters:
  delegateMethod - the name of the methodthat is called by $proceed().

The body of the created method is a copy of the body of a method specified by body. However, it is wrapped in parameter-conversion code.

The method specified by body must have this singature:

Object method(Object[] params, <type> cvalue)

The type of the cvalue depends on constParam. If constParam is null, the signature must be:

Object method(Object[] params)

The method body copied from body is wrapped in parameter-conversion code, which converts parameters specified by parameterTypes into an array of Object. The returned value is also converted from the Object type to the type specified by returnType. Thus, the resulting method body is as follows:

Object[] params = new Object[] { p0, p1, ... };
 <type> cvalue = <constant-value>;
 ... copied method body ...
 Object result = <returned value>
 return (<returnType>)result;
 

The variables p0, p2, ... represent formal parameters of the created method. The value of cvalue is specified by constParam.

If the type of a parameter or a returned value is a primitive type, then the value is converted into a wrapper object such as java.lang.Integer. If the type of the returned value is void, the returned value is discarded.

Example:

ClassPool pool = ... ;
 CtClass vec = pool.makeClass("intVector");
 vec.setSuperclass(pool.get("java.util.Vector"));
 CtMethod addMethod = pool.getMethod("Sample", "add0");
 CtClass[] argTypes = { CtClass.intType };
 CtMethod m = CtNewMethod.wrapped(CtClass.voidType, "add", argTypes,
 null, addMethod, null, vec);
 vec.addMethod(m);

where the class Sample is as follows:

public class Sample extends java.util.Vector {
 public Object add0(Object[] args) {
 super.addElement(args[0]);
 return null;
 }
 }

This program produces a class intVector:

public class intVector extends java.util.Vector {
 public void add(int p0) {
 Object[] args = new Object[] { p0 };
 // begin of copied body
 super.addElement(args[0]);
 Object result = null;
 // end
 }
 }

Note that the type of the parameter to add() depends only on the value of argTypes passed to CtNewMethod.wrapped(). Thus, it is easy to modify this program to produce a StringVector class, which is a vector containing only String objects, and other vector classes.
Parameters:
  returnType - the type of the returned value.
Parameters:
  mname - the method name.
Parameters:
  parameterTypes - a list of the parameter types.
Parameters:
  exceptionTypes - a list of the exception types.
Parameters:
  body - the method body(must not be a static method).
Parameters:
  constParam - the constant parameter(maybe null).
Parameters:
  declaring - the class to which the created method isadded.