org.jboss.seam.util
Class ProxyFactory

java.lang.Object
  org.jboss.seam.util.ProxyFactory

public class ProxyFactory
extends Object

Factory of dynamic proxy classes.

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.setHandler(mi);
 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();
 

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();
 

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

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

Here 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);
     }
 }
 

Since:

3.1

See Also:

MethodHandler

Field Summary

String

writeDirectory If the value of this variable is not null, the class file of the generated proxy class is written under the directory specified by this variable.

Constructor Summary

ProxyFactory()
Constructs a factory of proxy class.

Method Summary

Object	create(Class[] paramTypes, Object[] args) Creates a proxy class and returns an instance of that class.
Class	createClass() Generates a proxy class.
protected ClassLoader	getClassLoader()
protected ProtectionDomain	getDomain()
void	setFilter(javassist.util.proxy.MethodFilter mf) Sets a filter that selects the methods that will be controlled by a handler.
void	setHandler(javassist.util.proxy.MethodHandler mi) Sets the default invocation handler.
void	setInterfaces(Class[] ifs) Sets the interfaces of a proxy class.
void	setSuperclass(Class clazz) Sets the super class of a proxy class.

Methods inherited from class java.lang.Object

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

Field Detail

writeDirectory

public String writeDirectory

If the value of this variable is not null, the class file of the generated proxy class is written under the directory specified by this variable. For example, if the value is ".", then the class file is written under the current directory. This method is for debugging.

The default value is null.

Constructor Detail

ProxyFactory

public ProxyFactory()

Constructs a factory of proxy class.

Method Detail

setSuperclass

public void setSuperclass(Class clazz)

Sets the super class of a proxy class.

setInterfaces

public void setInterfaces(Class[] ifs)

Sets the interfaces of a proxy class.

setFilter

public void setFilter(javassist.util.proxy.MethodFilter mf)

Sets a filter that selects the methods that will be controlled by a handler.

createClass

public Class createClass()

Generates a proxy class.

getClassLoader

protected ClassLoader getClassLoader()

getDomain

protected ProtectionDomain getDomain()

create

public Object create(Class[] paramTypes,
                     Object[] args)
              throws NoSuchMethodException,
                     IllegalArgumentException,
                     InstantiationException,
                     IllegalAccessException,
                     InvocationTargetException

Creates a proxy class and returns an instance of that class.

Parameters:

paramTypes - parameter types for a constructor.

args - arguments passed to a constructor.

Throws:

NoSuchMethodException

IllegalArgumentException

InstantiationException

IllegalAccessException

InvocationTargetException

setHandler

public void setHandler(javassist.util.proxy.MethodHandler mi)

Sets the default invocation handler. This invocation handler is shared among all the instances of a proxy class unless another is explicitly specified.