Spring 中Ioc(控制反转) 用例 迎客

IoC全名Inversion of Control，中文称“控制反转”。和AOP一样，是Spring的核心技术。

这里举个例子，这说明一下IoC的应用。

接口 UserDao.java:

package com.springdemo.dao;

 public interface UserDao {
    public void save(String name,String password);
}

类 UserDaoImplForMysql.java:

package com.springdemo.dao;

 public class UserDaoImplForMysql implements UserDao {

    public void save(String name, String password) {
        System.out.println("UserDaoImplForMysql.....");
    }
}

类 UserDaoImplForOrcle.java:

package com.springdemo.dao;

 public class UserDaoImplForOrcle implements UserDao {

    public void save(String name, String password) {
        System.out.println("UserDaoImplForOrcle...");
    }
}

客户端类 Client.java:

package com.springdemo.client;

 import com.springdemo.dao.UserDaoImplForMysql;
 import com.springdemo.manager.UserManagerImpl;

public class Client {
    public static void main(String[] args) {
         UserManagerImpl userManager = new UserManagerImpl();
         userManager.setUserDao(new UserDaoImplForMysql());
         userManager.save("pxl", "pxl123");
    }
}

这里，如果想改用UserDaoImplForOrcle.java类，必须修改客户端代码。

下面引入IoC这重新实现客户。

配置Spring容器 bean.xml:

<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context"
    xmlns:util="http://www.springframework.org/schema/util"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context-3.0.xsd
        http://www.springframework.org/schema/util
        http://www.springframework.org/schema/util/spring-util-3.0.xsd">

    <bean id="UserDaoImplForMysql" class="com.springdemo.dao.UserDaoImplForMysql" />
    <bean id="UserDaoImplForOrcle" class="com.springdemo.dao.UserDaoImplForOrcle" />
    <bean id="UserManagerImpl" class="com.springdemo.manager.UserManagerImpl">
        <property name="userDao" ref="UserDaoImplForMysql"/>
    </bean>

 </beans>

修改客户端类 Client.java:

package com.springdemo.client;

 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.context.support.ClassPathXmlApplicationContext;
 import com.springdemo.manager.UserManagerImpl;

public class Client {
    public static void main(String[] args) {
//         UserManagerImpl userManager = new UserManagerImpl();
//         userManager.setUserDao(new UserDaoImplForMysql());
//         userManager.save("pxl", "pxl123");

        BeanFactory fac = new ClassPathXmlApplicationContext("bean.xml");  
        UserManagerImpl userDao = (UserManagerImpl) fac.getBean("UserManagerImpl");
        userDao.save("pxl", "pxl123");
    }
}

这样若想改用UserDaoImplForOrcle.java类，只须配置一下bean.xml文件即可。