spring的beans.xml的配置

 <?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">

   <!--接口注入,UserDAOImpl是实现UserDAO的接口类，主要就是实现数据库的操作，根据不同的数据库类型实现不同的类操作。-->
   <bean id="u" class="com.bjsxt.dao.impl.UserDAOImpl">
   </bean>

   <bean id="userService" class="com.bjsxt.service.UserService">
       <!--1、set方法注入，主要用这种方法。-->
       <property name="userDAO" ref="u" />
     <!--2、构造方法注入-->
     <!--
        <constructor-arg>
            <ref bean="u"/>
        </constructor-arg>
      -->
   </bean>
 </beans>

UserDAO.java如下：

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

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

UserDAOImpl.java如下：

 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!");
     }
 }

User.java如下：

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;
    }
}

UserService.java如下：

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

 public class UserService {
     private UserDAO userDAO;
     /*用于beans.xml中构造方法的注入使用的；
     public UserService(UserDAO userDAO){
         this.userDAO=userDAO;
     }
     */
     public void add(User user) {
         userDAO.save(user);
     }
     public UserDAO getUserDAO() {
         return userDAO;
     }
     public void setUserDAO(UserDAO userDAO) {
         this.userDAO = userDAO;
     }
 }

那么如何来使用呢？如下代码是写在测试单元中的：
UserServiceTest.java：

 package com.bjsxt.service;
 import org.junit.Test;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.support.ClassPathXmlApplicationContext;
 import com.bjsxt.model.User;

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

     @Test
     public void testAdd() throws Exception {
         /*读取beans.xml文件ClassPathXmlApplicationContext会把读取的内容放入到bean容器中；*/
         ApplicationContext ctx = new ClassPathXmlApplicationContext("beans.xml");
         /*读取注入*/
         UserService service = (UserService)ctx.getBean("userService");
         User u = new User();
         u.setUsername("zhangsan");
         u.setPassword("zhangsan");
         service.add(u);
     }
 }