通過面向接口編程實現日志輸出
(1)建立一個接口TimeBookInterface,代碼如下
/*******TimeBookInterface.java********/
package com.gc.dao;

public interface TimeBookInterface{

 public void doAuditing(String name);
}
(2)編寫接口實現類,代碼如下
/*******TimeBook.java********/
package com.gc.dao.impl;

public class TimeBook implements TimeBookInterface{

 public void doAuditing(String name){
 
  //審查數據的相關程序
  ......
 }
}
(3)編寫一個代理類,用來實現日志輸出,其代碼如下
/*******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;
 }
 //實際業務處理
 public void doAuditing(String name){
 
  logger.log(Level.INFO,name+"開始審核數據");
  timeBookInterface.doAuditing(name);
  logger.log(Level.INFO,name+"審核數據結束");
 }
}
(4)編寫測試代碼類
......
public static void main(String[] args){
//針對接口進行編程
 TimeBookProxy timeBookProxy = new TimeBookProxy(new TimeBook());
 timeBookProxy.doAuditing("張三");
}

 使用java的代理機制進行日志輸出
(1)編寫一個日志信息的代理類LogProxy,這個代理類實現了接口InvocationHandler,
 可以對任何接口實現日志信息的輸出.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;
//代理類實現了接口InvocationHandler
public class LogProxy implements InvocationHandler{

 private Logger logger = Logger.getLogger(this.getClass().getName());
 private Object delegate;
 //綁定對象
 public Object bing(Object delegate){
  this.delegate = delegate;
  return Proxy.new ProxyInstance(delegate.getClass().getClassLoader(),delegate.getClass().getInterfaces(),this);
 }
 //針對接口編程
 public Object invoke(Object proxy,Mehtod method,Object[] args)throws Throwable{
 
  Object result = null;
  try{
  //在方法調用前后進行日志輸出
   logger.log(Level.INFO,args[0] + "開始審核數據");
   result = method.invoke(delegate,args);
   logger.log(Level.INFO,args[0] + "審核數據結束");
  }
  catch(Exception e){
   logger.log(Level.INFO,e.toString());
  }
  return result;
 }
}
(2)建立一個接口TimeBookInterface,代碼如下
/*******TimeBookInterface.java********/
package com.gc.dao;

public interface TimeBookInterface{

 public void doAuditing(String name);
}
(3)編寫接口實現類,代碼如下
/*******TimeBook.java********/
package com.gc.dao.impl;

public class TimeBook implements TimeBookInterface{

 public void doAuditing(String name){
 
  //審查數據的相關程序
  ......
 }
}
(4)編寫測試代碼類
......
public static void main(String[] args){
 //實現了對日志類的重用
 LogProxy logProxy = new LogProxy();
 TimeBookInterface timeBookInterface = (TimeBookInterface)logProxy.bind(new TimeBook());
 timeBookProxy.doAuditing("張三");
}
代碼來自spring從入門到精通一書