Spring--AOP--面向切面编程

AOP: 面向切面编程. 通过动态代理实现.

AOP就3条线, 2条线给剪断.

实现:动态代理

如果实现interface的话, 用Proxy, InvocationHandler.

不实现interface的话, 用cglib操作二进制码实现.

AOP用在哪里:

性能, 日志, 权限检查, transaction.

项目里如何使用: 声明式事务管理.

 

JDK提供了两个提供动态代理的类: Proxy, InvocationHandler.

UserServiceTest.java:

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 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());		
	}	
}

代理 LogInterceptor.java:

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;
	}
}

UserDAOImpl.java:

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) {	
		System.out.println("user saved!");
	}

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

UserDAO.java:

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

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