动态代理总结

为了实现ocp的原则，需要加一个代理： 类似于AOP的切面的编程思想，扩展性更好。(内部的执行过程至今还搞不懂, 求大神指点)

其实以上代码还是很不好，重复的连接太多，可以这样改进，使用一个listener来连接，然后将conn对象放在application里面。

package com.huxin.dynamic_proxy;import java.lang.reflect.InvocationHandler;import java.lang.reflect.Method;import java.lang.reflect.Proxy;import org.omg.CORBA.SystemException;import org.omg.CORBA.portable.InputStream;import org.omg.CORBA.portable.InvokeHandler;import org.omg.CORBA.portable.OutputStream;import org.omg.CORBA.portable.ResponseHandler;public class LogHandler implements InvocationHandler {    private Object targetObject;     //生成一个动态代理的对象    public Object newDynamicproxy(Object targetObject){this.targetObject = targetObject;    return Proxy.newProxyInstance(targetObject.getClass().getClassLoader(),targetObject.getClass().getInterfaces(),this);    }    public Object invoke(Object proxy, Method method, Object[] args)throws Throwable {Object object = null;System.out.println(method.getName()+"方法开始之前被调用");//这句话才是真正调用它的方法object = method.invoke(this.targetObject, args);System.out.println(method.getName()+"方法开始之后被调用");return object;}}

package com.huxin.dynamic_proxy;public class Client {public static void main(String[] args) {LogHandler lh = new LogHandler();UserService userService = (UserService)lh.newDynamicproxy(new UserServiceImpl());String name = userService.findById("0001");System.out.println(name);}}

package com.huxin.dynamic_proxy;public class UserServiceImpl implements UserService {public void add(String userId, String name) {   System.out.println("add()");}public void modify(String userId, String name) {   System.out.println("modify()");}public String findById(String userId) {  System.out.println("findById()");  return "王八";}}

public interface UserService {   public void add(String userId,String name);   public void modify(String userId,String name);   public String findById(String userId);}

关于Service的启动connection的一个封装。

注意一：不要出现重复提交的问题

注意二：关于异常的处理，它会转换成InvocationTargetException的异常。

import java.lang.reflect.InvocationHandler;import java.lang.reflect.InvocationTargetException;import java.lang.reflect.Method;import java.lang.reflect.Proxy;import java.sql.Connection;import org.omg.CORBA.SystemException;import org.omg.CORBA.portable.InputStream;import org.omg.CORBA.portable.InvokeHandler;import org.omg.CORBA.portable.OutputStream;import org.omg.CORBA.portable.ResponseHandler;public class TransactionHandler implements InvocationHandler {private static TransactionHandler instance = new TransactionHandler();    private Object targetObject; private TransactionHandler(){}public  TransactionHandler getInstance(){return instance;}    //生成一个动态代理的对象    public  Object newDynamicproxy(Object targetObject){this.targetObject = targetObject;    return Proxy.newProxyInstance(targetObject.getClass().getClassLoader(),targetObject.getClass().getInterfaces(),this);    }    public Object invoke(Object proxy, Method method, Object[] args)throws Throwable {Connection conn = null;Object object = null;System.out.println(method.getName()+"方法开始之前被调用");try{conn = DBUtilPromote.getConnection();if(method.getName().startsWith("add")||method.getName().startsWith("del")||method.getName().startsWith("modify")){DBUtilPromote.setAutoCommit(conn, false);}//这句话才是真正调用它的方法object = method.invoke(this.targetObject, args);//注意这里：一定要进行判断，不然有可能重复提交，造成错误System.out.println(method.getName()+"方法开始之后被调用");if(!conn.getAutoCommit()){DBUtilPromote.commit(conn);}//注意：抛异常的时候，它会自动转成 InvocationTargetException，所以永远不会逮到AppException}catch(Exception e){e.printStackTrace();if(e instanceof  InvocationTargetException){InvocationTargetException invocationTargetException = (InvocationTargetException)e;throw invocationTargetException.getTargetException();}throw new RuntimeException("出现错误了");}return object;}}