通过面向接口编程实现日志输出
(1)建立一个接口TimeBookInterface,代码如下
/*******TimeBookInterface.java********/
package com.gc.dao;

public interface TimeBookInterface{

 public void doAuditing(String name);
}
(2)编写接口实现类,代码如下
/*******TimeBook.java********/
package com.gc.dao.impl;

public class TimeBook implements TimeBookInterface{

 public void doAuditing(String name){
 
  //审查数据的相关程序
  ......
 }
}
(3)编写一个代理类,用来实现日志输出,其代码如下
/*******TimeBookProxy.java********/
package com.gc.dao.impl;

import org.apache.log4j.Level;
import org.apache.log4j.Logger;

public class TimeBookProxy{

 private Logger logger = Logger.getLogger(this.getClass().getName());
 private TimeBookInterface timeBookInterface;
 public TimeBookProxy(TimeBookInterface timeBookInterface){
 
  this.timeBookInterface = timeBookInterface;
 }
 //实际业务处理
 public void doAuditing(String name){
 
  logger.log(Level.INFO,name+"开始审核数据");
  timeBookInterface.doAuditing(name);
  logger.log(Level.INFO,name+"审核数据结束");
 }
}
(4)编写测试代码类
......
public static void main(String[] args){
//针对接口进行编程
 TimeBookProxy timeBookProxy = new TimeBookProxy(new TimeBook());
 timeBookProxy.doAuditing("张三");
}

 使用java的代理机制进行日志输出
(1)编写一个日志信息的代理类LogProxy,这个代理类实现了接口InvocationHandler,
 可以对任何接口实现日志信息的输出.其代理如下
package com.gc.dao;

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

import org.apache.log4j.Level;
import org.apache.log4j.Logger;
//代理类实现了接口InvocationHandler
public class LogProxy implements InvocationHandler{

 private Logger logger = Logger.getLogger(this.getClass().getName());
 private Object delegate;
 //绑定对象
 public Object bing(Object delegate){
  this.delegate = delegate;
  return Proxy.new ProxyInstance(delegate.getClass().getClassLoader(),delegate.getClass().getInterfaces(),this);
 }
 //针对接口编程
 public Object invoke(Object proxy,Mehtod method,Object[] args)throws Throwable{
 
  Object result = null;
  try{
  //在方法调用前后进行日志输出
   logger.log(Level.INFO,args[0] + "开始审核数据");
   result = method.invoke(delegate,args);
   logger.log(Level.INFO,args[0] + "审核数据结束");
  }
  catch(Exception e){
   logger.log(Level.INFO,e.toString());
  }
  return result;
 }
}
(2)建立一个接口TimeBookInterface,代码如下
/*******TimeBookInterface.java********/
package com.gc.dao;

public interface TimeBookInterface{

 public void doAuditing(String name);
}
(3)编写接口实现类,代码如下
/*******TimeBook.java********/
package com.gc.dao.impl;

public class TimeBook implements TimeBookInterface{

 public void doAuditing(String name){
 
  //审查数据的相关程序
  ......
 }
}
(4)编写测试代码类
......
public static void main(String[] args){
 //实现了对日志类的重用
 LogProxy logProxy = new LogProxy();
 TimeBookInterface timeBookInterface = (TimeBookInterface)logProxy.bind(new TimeBook());
 timeBookProxy.doAuditing("张三");
}
代码来自spring从入门到精通一书