摘要：Spring AOP ，從代理機(jī)制看AOP，動(dòng)態(tài)代理的范例
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在JDK1.3之后加入了可協(xié)助開(kāi)發(fā)動(dòng)態(tài)代理功能的API，你不必為特定對(duì)象與方法編寫特定的代理對(duì)象，使用動(dòng)態(tài)代理，可以使用一個(gè)處理者（Handler）服務(wù)于各個(gè)對(duì)象。
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LogHandler.java
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package com.kela.spring.aop;
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import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
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import org.apache.log4j.Logger;
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public class LogHandler implements InvocationHandler {
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??? private Logger log = Logger.getLogger(this.getClass().getName());
???
??? private Object delegate;
???
??? public Object bind(Object delegate) {
??????? this.delegate = delegate;
??????? return Proxy.newProxyInstance(delegate.getClass().getClassLoader(), delegate.getClass().getInterfaces(), this);
??? }
??? public Object invoke(Object arg0, Method method, Object[] args)
??????????? throws Throwable {
??????? Object result = null;
???????
??????? try {
??????????? log.info("hello
方法開(kāi)始執(zhí)行... ...");
???????????
??????????? result = method.invoke(delegate, args);
???????????
??????????? log.info("hello
方法執(zhí)行完畢");
??????? } catch (Exception e) {
??????????? System.out.println("[ERROR]" + e.getMessage());
??????? }
??????? return result;
??? }
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}
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IHell.java
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package com.kela.spring.aop;
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public interface IHello {
??? public void hello(String name);
}
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HelloSpeaker.java
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package com.kela.spring.aop;
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public class HelloSpeaker implements IHello {
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??? public void hello(String name) {
??????? System.out.println("
你好，" + name);
??? }
}
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ProxyDemo.java
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package com.kela.spring.aop;
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public class ProxyDemo {
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??? public void method_2() {
??????? LogHandler logHandler = new LogHandler();
???????
??????? IHello helloProxy = (IHello)logHandler.bind(new HelloSpeaker());
???????
??????? helloProxy.hello("kela");
??? }
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??? public static void main(String[] args) {
??????? ProxyDemo proxyDemo = new ProxyDemo();
???????
??????? proxyDemo.method_2();
??? }
}
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學(xué)習(xí)小結(jié)
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使用代理對(duì)象將記錄等于業(yè)務(wù)邏輯無(wú)關(guān)的動(dòng)作或任務(wù)提取出來(lái)，設(shè)計(jì)為一個(gè)服務(wù)對(duì)象，如LogHandler和上一小節(jié)中的HelloProxy，這樣的對(duì)象稱之為切面（Aspect）。