RelaxedDuckType.java
上传用户:hengxinggs
上传日期:2008-01-15
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文件大小:2k
- /*
- * 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;
- import java.util.HashMap;
- /**
- * RelaxedDuckType. 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 relaxed DuckType. If a method in the interface is
- * not present on the underlying object, the proxy simply returns null.
- *
- * @author djo
- */
- public class RelaxedDuckType extends DuckType implements InvocationHandler {
- public static Object implement(Class interfaceToImplement, Object object) {
- return Proxy.newProxyInstance(interfaceToImplement.getClassLoader(),
- new Class[] {interfaceToImplement}, new RelaxedDuckType(object));
- }
-
- public static boolean includes(Object object, String method, Class[] args) {
- try {
- Method realMethod = object.getClass().getMethod(method, args);
- } catch (NoSuchMethodException e) {
- return false;
- }
- return true;
- }
-
- private static final HashMap NULL_VALUES = new HashMap(); {
- NULL_VALUES.put(Boolean.TYPE, Boolean.FALSE);
- NULL_VALUES.put(Integer.TYPE, new Integer(0));
- NULL_VALUES.put(Float.TYPE, new Float(0));
- NULL_VALUES.put(Long.TYPE, new Long(0));
- NULL_VALUES.put(Double.TYPE, new Double(0));
- NULL_VALUES.put(Character.TYPE, new Character(' '));
- }
-
- protected RelaxedDuckType(Object object) {
- super(object);
- }
-
- public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
- try {
- Method realMethod = objectClass.getMethod(method.getName(), method.getParameterTypes());
- return realMethod.invoke(object, args);
- } catch (NoSuchMethodException e) {
- return NULL_VALUES.get(method.getReturnType());
- } catch (Throwable t) {
- throw t;
- }
- }
- }