org.codehaus.groovy.runtime.ConversionHandler Maven / Gradle / Ivy
/*
* Copyright 2003-2007 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.codehaus.groovy.runtime;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
/**
* This class is a general adapter to map a call to an Java interface
* to a given delegate.
*
* @author Ben Yu
* @author Jochen Theodorou
*/
public abstract class ConversionHandler implements InvocationHandler {
private Object delegate;
/**
* Creates a ConversionHandler with an deleagte.
* @param delegate the delegate
* @throws IllegalArgumentException if the given delegate is null
*/
public ConversionHandler(Object delegate) {
if (delegate==null) throw new IllegalArgumentException("delegate must not be null");
this.delegate = delegate;
}
/**
* gets the delegate.
* @return the delegate
*/
public Object getDelegate(){
return delegate;
}
/**
* This method is a default implementation for the invoke method
* given in Invocationhandler. Any call to an method with an
* declaring class that is not Object is redirected to invokeCustom.
* Methods like tostring, equals and hashcode are called on the class
* itself instead of the delegate. It is better to overwrite the
* invokeCustom method where the Object related methods are filtered out.
*
* @see #invokeCustom(Object, Method, Object[])
* @see InvocationHandler#invoke(java.lang.Object, java.lang.reflect.Method, java.lang.Object[])
*
* @param proxy the proxy
* @param method the method
* @param args the arguments
* @return the result of the invocation by method or delegate
* @throws Throwable any exception caused by the delegate or the method
*/
public Object invoke(Object proxy, Method method, Object[] args)
throws Throwable {
if(!isObjectMethod(method)){
return invokeCustom(proxy,method,args);
}
try {
return method.invoke(this, args);
} catch (InvocationTargetException ite) {
throw ite.getTargetException();
}
}
/**
* This method is called for all Methods not defined on Object.
* The delegate should be called here.
*
* @param proxy the proxy
* @param method the method
* @param args the arguments
* @return the result of the invocation of the delegate
* @throws Throwable any exception causes by the delegate
* @see #invoke(Object, Method, Object[])
* @see InvocationHandler#invoke(java.lang.Object, java.lang.reflect.Method, java.lang.Object[])
*
*/
public abstract Object invokeCustom(Object proxy, Method method, Object[] args) throws Throwable;
/**
* Indicates whether some other object is "equal to" this one.
* The delegate is used if the class of the parameter and the
* current class are equal. In other cases the method will return
* false. The exact class is here used, if inheritance is needed,
* this method must be overwritten.
*
* @see java.lang.Object#equals(java.lang.Object)
*/
public boolean equals(Object obj) {
if (obj instanceof Proxy){
obj = Proxy.getInvocationHandler(obj);
}
if (obj instanceof ConversionHandler){
return (((ConversionHandler)obj).getDelegate()).equals(delegate);
} else {
return false;
}
}
/**
* Returns a hash code value for the delegate.
* @see java.lang.Object#hashCode()
*/
public int hashCode() {
return delegate.hashCode();
}
/**
* Returns a String version of the delegate.
* @see java.lang.Object#toString()
*/
public String toString() {
return delegate.toString();
}
private static boolean isObjectMethod(Method mtd){
return mtd.getDeclaringClass().equals(Object.class);
}
}