Spring学习-4-手动实现AOP编程

AOP面向切面编程

AOP可以实现“业务代码”和“关注点代码”完全分离

  @Override
    public List<Message> findAllMessage() {

        Session session = null;  //关注点代码
        Transaction tx = null;

        try{

            session = HibernateUtils.getSession();

            tx = session.beginTransaction();  //关注点代码

            Query q = session.createQuery("from Message order by write_time desc "); //业务代码

            return q.list();  //业务代码

        }catch (Exception e){

            throw new RuntimeException(e);  //关注点代码
        }finally {

            tx.commit();
            session.close();  //关注点代码

        }

    }

分析：

关注点代码，就是指重复执行的代码。

业务代码和关注点代码分离，好处？

--关注点代码写一次即可

--开发者只需要关注核心业务

--运行期间，执行业务代码的时候动态的植入关注点代码;(代理实现)

如何分离

过程式/对象式/代理模式分离

手动实现aop编程实例一:

package aop;

import org.springframework.stereotype.Component;

/**
 * Created by cxspace on 16-8-10.
 */

@Component //加入ioc容器

public class Aop {
    //重复执行的代码
    public void begin(){
        System.out.println("开始事务");
    }

    public void commite(){
        System.out.println("提交事务");
    }

}

package aop;

/**
 * Created by cxspace on 16-8-10.
 */
public interface IUserDao {
    public void save();
}

package aop;

import org.springframework.stereotype.Component;

import javax.annotation.Resource;

/**
 * Created by cxspace on 16-8-10.
 */

@Component
public class UserDao implements IUserDao{

    @Resource
    private Aop aop;

    @Override
    public void save() {
        aop.begin();
        System.out.println("保存数据！");
        aop.commite();
    }
}

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:p="http://www.springframework.org/schema/p"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="
        http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context.xsd">

    <!--开启注解扫描-->
    <context:component-scan base-package="aop"></context:component-scan>

</beans>

package aop;

import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * Created by cxspace on 16-8-10.
 */
public class App {

    ApplicationContext ac = new ClassPathXmlApplicationContext("aop/bean.xml");

    @Test
    public void test(){

        IUserDao userDao = (IUserDao)ac.getBean("userDao");
        userDao.save();

    }
}

手动实现AOP编程实例二（代理）

package aopProxy;

/**
 * Created by cxspace on 16-8-10.
 */
public interface IUserDao {
    public void save();
}

package aopProxy;

import org.springframework.stereotype.Component;

/**
 * Created by cxspace on 16-8-10.
 */

@Component
public class UserDao implements IUserDao {

    @Override
    public void save() {

        System.out.println("保存数据！");

    }
}

package aopProxy;

import org.springframework.stereotype.Component;

/**
 * Created by cxspace on 16-8-10.
 */

@Component //加入ioc容器

public class Aop {
    //重复执行的代码
    public void begin(){
        System.out.println("开始事务");
    }

    public void commite(){
        System.out.println("提交事务");
    }

}

package aopProxy;

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

/**
 * Created by cxspace on 16-8-10.
 */
public class ProxyFactory {

    //目标对象
    private static Object target;

    private static Aop aop;

    //生成代理对象方法
    public static Object getProxyInstance(Object target_,Aop aop_){

        target = target_;
        aop = aop_;

        return Proxy.newProxyInstance(
                target.getClass().getClassLoader(),
                target.getClass().getInterfaces(),
                new InvocationHandler() {
                    @Override
                    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {

                        aop.begin();

                        Object returnValue = method.invoke(target,args);

                        aop.commite();

                        return returnValue;
                    }
                }
        );

    }
}

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:p="http://www.springframework.org/schema/p"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="
        http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context.xsd">

    <!--开启注解扫描-->
    <context:component-scan base-package="aopProxy"></context:component-scan>

    <!--调用工厂方法,返回UserDao代理后的对象-->
    <bean id="userDao_proxy" class="aopProxy.ProxyFactory" factory-method="getProxyInstance">
        <constructor-arg index="0" ref="userDao"></constructor-arg>
        <constructor-arg index="1" ref="aop"></constructor-arg>
    </bean>

</beans>

package aopProxy;

import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * Created by cxspace on 16-8-10.
 */
public class App {

    ApplicationContext ac = new ClassPathXmlApplicationContext("aopProxy/bean.xml");

    @Test
    public void test(){

        IUserDao userDao = (IUserDao)ac.getBean("userDao_proxy");

        System.out.println(userDao.getClass());

        userDao.save();

    }

}