[Java] Spring_1400_AOP_Introduction

13, AOP
  @1, 慎用继承 (因为继承直接就写死了！)
     经常组合代替了继承，组合灵活性更高！
  @2, Spring 解决了单例的问题
   动态代理 jdk 如果想产生动态代理，那么这个类就需要实现一个接口，没有implements接口的类，JDK是给它产生不了动态代理的。 
   jdk proxy invocationhander

package com.bjsxt.aop;

LogInterceptor        很好！很好！写的！

package com.bjsxt.aop;

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

public class LogInterceptor implements InvocationHandler {
	private Object target;
	
	public Object getTarget() {
		return target;
	}

	public void setTarget(Object target) {
		this.target = target;
	}

	public void beforeMethod(Method m) {
		
		System.out.println(m.getName() + " start");
	}

	public Object invoke(Object proxy, Method m, Object[] args)
			throws Throwable {
		beforeMethod(m);
		m.invoke(target, args);
		return null;
	}
}

package com.bjsxt.dao;

interface UserDAO

package com.bjsxt.dao;
import com.bjsxt.model.User;

public interface UserDAO {
	public void save(User user);
	public void delete();
}

package com.bjsxt.dao.impl;

UserDAOImpl

package com.bjsxt.dao.impl;

import com.bjsxt.dao.UserDAO;
import com.bjsxt.model.User;


public class UserDAOImpl implements UserDAO {

	public void save(User user) {
		
		//Hibernate
		//JDBC
		//XML
		//NetWork
		System.out.println("user saved!");
	}

	public void delete() {
		System.out.println("user deteleted");
	}

}

UserDAOImpl2  extends  UserDAOImpl  继承的方式

package com.bjsxt.dao.impl;

import com.bjsxt.model.User;

public class UserDAOImpl2 extends UserDAOImpl {
	@Override
	public void save(User user) {
		
		System.out.println("save start...");
		super.save(user);
		
	}
}

UserDAOImpl3 implements UserDAO  实现接口的方式

package com.bjsxt.dao.impl;

import com.bjsxt.aop.LogInterceptor;
import com.bjsxt.dao.UserDAO;
import com.bjsxt.model.User;

public class UserDAOImpl3 implements UserDAO {
	
	private UserDAO userDAO = new UserDAOImpl();
	
	public void save(User user) {
		
		new LogInterceptor().beforeMethod(null);
		userDAO.save(user);
		
		
	}

	public void delete() {
		// TODO Auto-generated method stub
		
	}
}

packagecom.bjsxt.model;

User  (用户类 ： 具有 名字 和 密码 两个属性)

package com.bjsxt.model;

public class User {
	private String username;
	private String password;
	public String getUsername() {
		return username;
	}
	public void setUsername(String username) {
		this.username = username;
	}
	public String getPassword() {
		return password;
	}
	public void setPassword(String password) {
		this.password = password;
	}
}

package com.bjsxt.service;
UserService  用户服务层

package com.bjsxt.service;

import com.bjsxt.dao.UserDAO;
import com.bjsxt.model.User;

public class UserService {
	private UserDAO userDAO;

	public void add(User user) {
		userDAO.save(user);
	}

	public UserDAO getUserDAO() {
		return userDAO;
	}

	public void setUserDAO(UserDAO userDAO) {
		this.userDAO = userDAO;
	}
}

packagecom.bjsxt.spring;
interface BeanFactory

package com.bjsxt.spring;

public interface BeanFactory {
	public Object getBean(String id);
}

ClassPathXmlApplicationContext

package com.bjsxt.spring;


import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.jdom.Document;
import org.jdom.Element;
import org.jdom.input.SAXBuilder;

public class ClassPathXmlApplicationContext implements BeanFactory {
	
	private Map<String , Object> beans = new HashMap<String, Object>();
	
	
	//IOC Inverse of Control DI Dependency Injection
	public ClassPathXmlApplicationContext() throws Exception {
		SAXBuilder sb=new SAXBuilder();
	    
	    Document doc=sb.build(this.getClass().getClassLoader().getResourceAsStream("beans.xml")); //构造文档对象
	    Element root=doc.getRootElement(); //获取根元素HD
	    List list=root.getChildren("bean");//取名字为disk的所有元素
	    for(int i=0;i<list.size();i++){
	       Element element=(Element)list.get(i);
	       String id=element.getAttributeValue("id");
	       String clazz=element.getAttributeValue("class");
	       Object o = Class.forName(clazz).newInstance();
	       System.out.println(id);
	       System.out.println(clazz);
	       beans.put(id, o);
	       
	       for(Element propertyElement : (List<Element>)element.getChildren("property")) {
	    	   String name = propertyElement.getAttributeValue("name"); //userDAO
	    	   String bean = propertyElement.getAttributeValue("bean"); //u
	    	   Object beanObject = beans.get(bean);//UserDAOImpl instance
	    	   
	    	   String methodName = "set" + name.substring(0, 1).toUpperCase() + name.substring(1);
	    	   System.out.println("method name = " + methodName);
	    	   
	    	   Method m = o.getClass().getMethod(methodName, beanObject.getClass().getInterfaces()[0]);
	    	   m.invoke(o, beanObject);
	       }
	       
	       
	    }  
	  
	}



	public Object getBean(String id) {
		return beans.get(id);
	}

}

beans.xml

<beans>
	<bean id="u" class="com.bjsxt.dao.impl.UserDAOImpl" >
		
	</bean>
	<bean id="userService" class="com.bjsxt.service.UserService" >
		<property name="userDAO" bean="u"/>
	</bean>
	
</beans>

Test 目录

package com.bjsxt.service;

package com.bjsxt.service;
import java.lang.reflect.Proxy;

import org.junit.Test;

import com.bjsxt.aop.LogInterceptor;
import com.bjsxt.dao.UserDAO;
import com.bjsxt.dao.impl.UserDAOImpl;
import com.bjsxt.model.User;
import com.bjsxt.spring.BeanFactory;
import com.bjsxt.spring.ClassPathXmlApplicationContext;


public class UserServiceTest {

	@Test
	public void testAdd() throws Exception {
		BeanFactory applicationContext = new ClassPathXmlApplicationContext();
		
		
		UserService service = (UserService)applicationContext.getBean("userService");
			
		
		User u = new User();
		u.setUsername("zhangsan");
		u.setPassword("zhangsan");
		service.add(u);
	}
	
	@Test
	public void testProxy() {
		UserDAO userDAO = new UserDAOImpl();
		LogInterceptor li = new LogInterceptor();
		li.setTarget(userDAO);
		UserDAO userDAOProxy = (UserDAO)Proxy.newProxyInstance(userDAO.getClass().getClassLoader(), userDAO.getClass().getInterfaces(), li);
		System.out.println(userDAOProxy.getClass());
		userDAOProxy.delete();
		userDAOProxy.save(new User());
		
	}
	
	/*class $Proxy4 implements UserDAO 
	 * {
	 * 	save(User u) {
	 * 	Method m = UserDAO.getclass.getmethod 
	 * li.invoke(this, m, u)
	 * }
	 * }
	 */

}

14, 
  UserDAO userDAO = new UserDAOImpl();
  LogInterceptor li = new LogInterceptor();
  li.setTarget(userDAO);
  UserDAO userDAOProxy = (UserDAO)Proxy.newProxyInstance(userDAO.getClass().getClassLoader(), userDAO.getClass().getInterfaces(), li);
(1), 产生的代理对象的 classLoader 和 被代理对象的 classLoader 要一样，因为代理对象中有一个 被代理对象，所以需要互相访问。
(2), userDAO.getClass().getInterfaces() 代理类(对象) 要实现这个接口。
(3), 第三个参数，代理用哪一个 Handler 进行处理。
(4), 因为代理类实现了 UserDAO 接口，抽象主题，所以进行强制转换。(UserDAO)
  System.out.println(userDAOProxy.getClass());
  userDAOProxy.delete();
  userDAOProxy.save(new User());
  写程序推荐，面向接口编程。