java对于接口和抽象类的代理实现，不需要有具体实现类

原文链接：http://www.javaarch.net/jiagoushi/835.htm

 

java对于接口和抽象类的代理实现，不需要有具体实现类

在某些场景下，可能我们只需要定义接口或者抽象类，而具体实现或者可以从接口的annotation就可以知道具体实现，后者具体实现由其他动态语言实现，或者需要实现AOP的一些其他功能，我们不需要具体实现，那么我们有哪些方法可以来实现这样的功能呢？

1.使用java.lang.reflect.Proxy代理类

 

	import java.awt.event.ActionListener;
	import java.lang.reflect.InvocationHandler;
	import java.lang.reflect.Method;
	import java.lang.reflect.Proxy;


	public class ProxyTest {

		public static void main(String[] args) {

			ClassLoader cl = ProxyTest.class.getClassLoader();
			Class[] interfaces = new Class[]{ ActionListener.class };
			
			Object object = Proxy.newProxyInstance(cl, interfaces, new InvocationHandler() {

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

					String name = method.getName();

					if(name.equals("toString")) {
						
						return "toString was called";
					}
					else if(name.equals("actionPerformed")) {
						
						System.out.println("actionPerformed was called");
						
						return null;
					}

					throw new RuntimeException("no method found");
				}
			});
			
		((ActionListener) object).actionPerformed(null);
		}
	}

输出：
   actionPerformed was called


2.通过javassist的javassist.util.proxy.ProxyFactory来实现

 

 

public class Test {

		public static void main(String[] args) throws Exception {

			ProxyFactory factory = new ProxyFactory();
		
				factory.setInterfaces(new Class[] { ActionListener.class });

				factory.setHandler(new MethodHandler() {
				
			public Object invoke(Object arg0, Method method, Method arg2, Object[] arg3) throws Throwable {
				
						String name = method.getName();

						if(name.equals("toString")) {
						
							return "toString was called";
						}
						else if(name.equals("actionPerformed")) {
						
						System.out.println("actionPerformed was called");
						
						return null;
						}

						throw new RuntimeException("no method found");
			}
			});
			
			Class c = factory.createClass();

			Object object = c.newInstance();
			 
			((ActionListener) object).actionPerformed(null);
		}
	}

这里主要的不同是factory.setSuperclass(MouseAdapter.class);这是设置抽象类接口


对于之前我们描述的http://blog.youkuaiyun.com/zhongweijian/article/details/8475086 利用spring AOP和Annotation来简化DAO实现就可以使用这种方式了。