Package mondrian.util

Class DelegatingInvocationHandler

java.lang.Object

mondrian.util.DelegatingInvocationHandler

All Implemented Interfaces:

InvocationHandler

Direct Known Subclasses:

SqlStatement.MyDelegatingInvocationHandler

public abstract class DelegatingInvocationHandler
extends Object
implements InvocationHandler

A class derived from DelegatingInvocationHandler handles a method call by looking for a method in itself with identical parameters. If no such method is found, it forwards the call to a fallback object, which must implement all of the interfaces which this proxy implements.

It is useful in creating a wrapper class around an interface which may change over time.

Example:

import java.sql.Connection;
 Connection connection = ...;
 Connection tracingConnection = (Connection) Proxy.newProxyInstance(
     null,
     new Class[] {Connection.class},
     new DelegatingInvocationHandler() {
         protected Object getTarget() {
             return connection;
         }
         Statement createStatement() {
             System.out.println("statement created");
             return connection.createStatement();
         }
     });

Author:

jhyde

Constructor Summary

Constructors

Constructor	Description
DelegatingInvocationHandler()

Method Summary

Modifier and Type	Method	Description
protected Object	getTarget()	Returns the object to forward method calls to, should the derived class not implement the method.
Object	invoke(Object proxy, Method method, Object[] args)

Methods inherited from class java.lang.Object

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

Constructor Detail

DelegatingInvocationHandler

public DelegatingInvocationHandler()

Method Detail

invoke

public Object invoke(Object proxy,
                     Method method,
                     Object[] args)
              throws Throwable

Specified by:

invoke in interface InvocationHandler

Throws:

Throwable

getTarget

protected Object getTarget()
                    throws InvocationTargetException

Returns the object to forward method calls to, should the derived class not implement the method. Generally, this object will be a member of the derived class, supplied as a parameter to its constructor.

The default implementation returns null, which will cause the invoke(Object, java.lang.reflect.Method, Object[]) method to throw an UnsupportedOperationException if the derived class does not have the required method.

Returns:

object to forward method calls to

Throws:

InvocationTargetException - if there is an error acquiring the target