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);
    }
}