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Groovy: A powerful, dynamic language for the JVM
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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 groovy.lang.GroovyObject;
import groovy.lang.GroovyRuntimeException;
import groovy.lang.GroovySystem;
import groovy.lang.MetaClass;
import org.codehaus.groovy.runtime.metaclass.MetaClassRegistryImpl;
import org.codehaus.groovy.vmplugin.VMPlugin;
import org.codehaus.groovy.vmplugin.VMPluginFactory;
import java.io.Serializable;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.lang.reflect.Proxy;
import java.util.concurrent.ConcurrentHashMap;
/**
* This class is a general adapter to map a call to a Java interface
* to a given delegate.
*
* @author Ben Yu
* @author Jochen Theodorou
*/
public abstract class ConversionHandler implements InvocationHandler, Serializable {
private final Object delegate;
private static final long serialVersionUID = 1162833717190835227L;
private final ConcurrentHashMap handleCache;
{
if (VMPluginFactory.getPlugin().getVersion() >= 7) {
handleCache = new ConcurrentHashMap(16, 0.9f, 2);
} else {
handleCache = null;
}
}
private MetaClass metaClass;
/**
* Creates a ConversionHandler with an delegate.
*
* @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;
}
/**
* Returns 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 a method with a declaring class that is
* not Object, excluding toString() and default methods is redirected to invokeCustom.
*
* Methods like equals and hashcode are called on the class itself instead
* of the delegate because they are considered fundamental methods that should
* not be overwritten. The toString() method gets special treatment as it is
* deemed to be a method that you might wish to override when called from Groovy.
* Interface default methods from Java 8 on the other hand are considered being
* default implementations you don't normally want to change. So they are called
* directly too
*
* In many scenarios, it is better to overwrite the invokeCustom method where
* the core Object related methods are filtered out.
*
* @param proxy the proxy
* @param method the method
* @param args the arguments
* @return the result of the invocation by method or delegate
* @throws Throwable if caused by the delegate or the method
* @see #invokeCustom(Object, Method, Object[])
* @see InvocationHandler#invoke(java.lang.Object, java.lang.reflect.Method, java.lang.Object[])
*/
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
if (handleCache != null && isDefaultMethod(method)) {
VMPlugin plugin = VMPluginFactory.getPlugin();
Object handle = handleCache.get(method);
if (handle == null) {
handle = plugin.getInvokeSpecialHandle(method, proxy);
handleCache.put(method, handle);
}
return plugin.invokeHandle(handle, args);
}
if (!checkMethod(method)) {
try {
if (method.getDeclaringClass() == GroovyObject.class) {
if ("getMetaClass".equals(method.getName())) {
return getMetaClass(proxy);
} else if ("setMetaClass".equals(method.getName())) {
return setMetaClass((MetaClass) args[0]);
}
}
return invokeCustom(proxy, method, args);
} catch (GroovyRuntimeException gre) {
throw ScriptBytecodeAdapter.unwrap(gre);
}
}
try {
return method.invoke(this, args);
} catch (InvocationTargetException ite) {
throw ite.getTargetException();
}
}
protected boolean isDefaultMethod(Method method) {
return ((method.getModifiers() & (Modifier.ABSTRACT | Modifier.PUBLIC | Modifier.STATIC)) ==
Modifier.PUBLIC) && method.getDeclaringClass().isInterface();
}
protected boolean checkMethod(Method method) {
return isCoreObjectMethod(method);
}
/**
* 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();
}
/**
* Checks whether a method is a core method from java.lang.Object.
* Such methods often receive special treatment because they are
* deemed fundamental enough to not be tampered with.
*
* @param method the method to check
* @return true if the method is deemed to be a core method
*/
public static boolean isCoreObjectMethod(Method method) {
return Object.class.equals(method.getDeclaringClass());
}
private MetaClass setMetaClass(MetaClass mc) {
metaClass = mc;
return mc;
}
private MetaClass getMetaClass(Object proxy) {
MetaClass mc = metaClass;
if (mc == null) {
mc = ((MetaClassRegistryImpl) GroovySystem.getMetaClassRegistry()).getMetaClass(proxy);
metaClass = mc;
}
return mc;
}
}