利用java.lang.reflect包中的InvocationHandler、Proxy實現代理(攔截已有方法)

本來想自己寫一個日志的，發現有位老兄寫的很好，我就不用費事，直接貼過來做筆記好了。
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[轉自： http://publishblog.blogdriver.com/blog/tb.b?diaryID=842351 ]

[Java]使用Proxy和InvocationHandler實現代理器模式

• 元對象(被代理對象):

package com.zj.gof.proxy;

public interface StudentInfoService {
?void findInfo(String studentName);
}

package com.zj.gof.proxy;

public class StudentInfoServiceImpl implements StudentInfoService {
?public void findInfo(String name) {
??System.out.println("你目前輸入的名字是:" + name);
?}
}

• 代理對象:

package com.zj.gof.proxy;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;

import org.apache.log4j.Logger;

public class LogHandler implements InvocationHandler {
? private Object proxyObj;
? private static Logger log=Logger.getLogger(LogHandler.class);
?
? public Object bind(Object obj){
?? this.proxyObj=obj;
?? return Proxy.newProxyInstance(obj.getClass().getClassLoader(),obj.getClass().getInterfaces(),this);
? }
?
? public Object invoke(Object proxy,Method method,Object[] args) throws Throwable{
?? Object result=null;
?? try{
??? //請在這里插入代碼，在方法前調用
??? log.info("調用log日志方法"+method.getName());
??? result=method.invoke(proxyObj,args); //原方法
??? //請在這里插入代碼，方法后調用
?? }catch(Exception e){
??? e.printStackTrace();
?? }
?? return result;
? }

}

注意:通過InvocationHandler接口實現的代理器只能代理接口方法. (這點在InvocationHandler的注解中有說明)

• 代理工廠:

package com.zj.gof.proxy;

public class LogFactory {
?private static Object getClassInstance(String clzName) {
??Object obj = null;
??try {
???Class cls = Class.forName(clzName);
???obj = (Object) cls.newInstance();
??} catch (ClassNotFoundException cnfe) {
???System.out.println("ClassNotFoundException:" + cnfe.getMessage());
??} catch (Exception e) {
???e.printStackTrace();
??}
??return obj;
?}

?public static Object getAOPProxyedObject(String clzName) {
??Object proxy = null;
??LogHandler handler = new LogHandler();
??Object obj = getClassInstance(clzName);
??if (obj != null) {
???proxy = handler.bind(obj);
??} else {
???System.out.println("Can't get the proxyobj");
???//throw
??}
??return proxy;
?}

}

• 客戶端調用:

package com.zj.gof.proxy;

public class MainTest {

?public static void main(String[] args) {
??//??PropertyConfigurator.configure("d:/log4j.properties");
??BasicConfigurator.configure();
??StudentInfoService studentInfo = (StudentInfoService) LogFactory
????.getAOPProxyedObject("com.zj.gof.proxy.StudentInfoServiceImpl");
??studentInfo.findInfo("阿飛");
?}
}

• 運行結果:

0 [main] INFO root? - 調用log日志方法findInfo
你目前輸入的名字是:阿飛

posted on 2007-09-18 17:45 心硯 閱讀(2681) 評論(0)  編輯  收藏 所屬分類: Java