DuckType.java
上传用户:hengxinggs
上传日期:2008-01-15
资源大小:212k
文件大小:3k
- /*
- * Copyright (C) 2005 db4objects Inc. http://www.db4o.com
- *
- * All rights reserved. This program and the accompanying materials
- * are made available under the terms of the Eclipse Public License v1.0
- * which accompanies this distribution, and is available at
- * http://www.eclipse.org/legal/epl-v10.html
- *
- * Contributors:
- * db4objects - Initial API and implementation
- */
- package org.eclipse.jface.examples.databinding.compositetable.reflect;
- import java.lang.reflect.InvocationHandler;
- import java.lang.reflect.Method;
- import java.lang.reflect.Proxy;
- /**
- * DuckType. Implements Duck Typing for Java. ("If it walks like a duck,
- * quacks like a duck, it..."). Essentially allows programs to treat
- * objects from separate hierarchies as if they were designed with common
- * interfaces as long as they adhere to common naming conventions.
- * <p>
- * This version is the strict DuckType. All methods present in
- * interfaceToImplement must be present on the target object.
- *
- * @author djo
- */
- public class DuckType implements InvocationHandler {
- /**
- * Causes object to implement the interfaceToImplement and returns
- * an instance of the object implementing interfaceToImplement even
- * if interfaceToImplement was not declared in object.getClass()'s
- * implements declaration.<p>
- *
- * This works as long as all methods declared in interfaceToImplement
- * are present on object.
- *
- * @param interfaceToImplement The Java class of the interface to implement
- * @param object The object to force to implement interfaceToImplement
- * @return object, but now implementing interfaceToImplement
- */
- public static Object implement(Class interfaceToImplement, Object object) {
- return Proxy.newProxyInstance(interfaceToImplement.getClassLoader(),
- new Class[] {interfaceToImplement}, new DuckType(object));
- }
-
- /**
- * Indicates if object is a (DuckType) instace of intrface. That is,
- * is every method in intrface present on object.
- *
- * @param intrface The interface to implement
- * @param object The object to test
- * @return true if every method in intrface is present on object. false otherwise
- */
- public static boolean instanceOf(Class intrface, Object object) {
- final Method[] methods = intrface.getMethods();
- Class candclass=object.getClass();
- for (int methodidx = 0; methodidx < methods.length; methodidx++) {
- Method method=methods[methodidx];
- try {
- candclass.getMethod(method.getName(), method.getParameterTypes());
- } catch (NoSuchMethodException e) {
- return false;
- }
- }
- return true;
- }
-
- protected DuckType(Object object) {
- this.object = object;
- this.objectClass = object.getClass();
- }
- protected Object object;
- protected Class objectClass;
-
- public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
- Method realMethod = objectClass.getMethod(method.getName(), method.getParameterTypes());
- return realMethod.invoke(object, args);
- }
- }