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

This factory generates a class that extends the given super class and implements the given interfaces. The calls of the methods inherited from the super class are forwarded and then invoke() is called on the method handler associated with the generated class. The calls of the methods from the interfaces are also forwarded to the method handler.

For example, if the following code is executed,

 ProxyFactory f = new ProxyFactory();
 f.setSuperclass(Foo.class);
 MethodHandler mi = new MethodHandler() {
 public Object invoke(Object self, Method m, Method proceed,
 Object[] args) throws Throwable {
 System.out.println("Name: " + m.getName());
 return proceed.invoke(self, args);  // execute the original method.
 }
 };
 f.setFilter(new MethodFilter() {
 public boolean isHandled(Method m) {
 // ignore finalize()
 return !m.getName().equals("finalize");
 }
 });
 Class c = f.createClass();
 Foo foo = (Foo)c.newInstance();
 ((ProxyObject)foo).setHandler(mi);
 

Then, the following method call will be forwarded to MethodHandler mi and prints a message before executing the originally called method bar() in Foo.

 foo.bar();
 

The last three lines of the code shown above can be replaced with a call to the helper method create, which generates a proxy class, instantiates it, and sets the method handler of the instance:

 :
 Foo foo = (Foo)f.create(new Class[0], new Object[0], mi);
 

To change the method handler during runtime, execute the following code:

 MethodHandler mi2 = ... ;    // another handler
 ((ProxyObject)foo).setHandler(mi2);
 

You can also specify the default method handler:

 ProxyFactory f2 = new ProxyFactory();
 f2.setSuperclass(Foo.class);
 f2.setHandler(mi);            // set the default handler
 Class c2 = f2.createClass();
 

The default handler is implicitly attached to an instance of the generated class c2. Calling setHandler on the instance is not necessary unless another method handler must be attached to the instance.

The following code is an example of method handler. It does not execute anything except invoking the original method:

 class SimpleHandler implements MethodHandler {
 public Object invoke(Object self, Method m,
 Method proceed, Object[] args) throws Exception {
 return proceed.invoke(self, args);
 }
 }
 

A proxy object generated by ProxyFactory is serializable if its super class or interfaces implement a java.io.Serializable. However, a serialized proxy object will not be compatible with future releases. The serialization support should be used for short-term storage or RMI.
See Also:   MethodHandler
since:
   3.1

The value of this field can be updated for changing the default implementation.

Example:

 ProxyFactory.classLoaderProvider = new ProxyFactory.ClassLoaderProvider() {
 public ClassLoader get(ProxyFactory pf) {
 return Thread.currentThread().getContextClassLoader();
 }
 };
 

The default value is null.