尚学堂Spring视频教程（二）：Spring控制反转

用Spring来实现IOC

在上节中我们自定义了一个接口BeanFactory和类ClassPathXmlApplicationContext来模拟Spring，其实它们在Spring中确实是存在的，下面我们具体来看看Spring的控制反转是如何操作的

其他代码一样，只是配置文件和单元测试的代码有点不同，注意引用其他bean配置的是"ref"属性

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
           http://www.springframework.org/schema/beans/spring-beans-2.5.xsd">

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

  </bean>

</beans>

配置文件

package com.bjsxt.service;
import org.junit.Test;

import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.xml.XmlBeanFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.core.io.ClassPathResource;

import com.bjsxt.model.User;

//Dependency Injection
//Inverse of Control
public class UserServiceTest {

    @Test
    public void testAdd() throws Exception {
        BeanFactory ctx = new ClassPathXmlApplicationContext("beans.xml");

        UserService service = (UserService)ctx.getBean("userService");

        User u = new User();
        u.setUsername("zhangsan");
        u.setPassword("zhangsan");
        service.add(u);
    }

}

测试代码

注：ClassPathXmlApplicationContext继承ApplicationContext，ApplicationContext又继承BeanFactory，所以也可以这样写ApplicationContext ctx = new ClassPathXmlApplicationContext("beans.xml");推荐使用这种写法。其构造函数也可以传入String数组，适用于多个配置文件的情况