Mybatis入门2-动态代理实现CRUD

MyBatis动态代理生成DAO的步骤：

1） 编写数据管理的接口XxxMapper

2） 编写该接口对应的Mapper.xml

a) namespace必须与Mapper接口全名一致

b) statement的id必须和Mapper接口中的对应方法名一致

c) statement的resultType必须和Mapper接口中对应方法返回值一致

3） 通过SqlSession的getMapper(XxxMapper.class)方法来获取动态代理的Mapper实现类对象

开发中运用动态代理的比较多，下面简单的介绍一个简单的案例关于增删改查的测试:

1.编写相应的接口

  public interface UserMapper {
      
      /**根据id查询用户
       * @param id
       * @return
       */
      public User queryUserById(Long id);
      
      /**查询全部的用户
      * @return
      */
     public List<User> queryAll();
     
     /**增加用户
      * @param user
      */
     public void insertUser(User user);
     
     
     /**更新用户
      * @param user
      */
     public void updateUser(User user);
     
     
     /**
      * 删除用户
      * @param id
      */
     public void deleteById(Long id);
 }

2.编写主配置文件

 <?xml version="1.0" encoding="UTF-8" ?>
  <!DOCTYPE configuration
    PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
    "http://mybatis.org/dtd/mybatis-3-config.dtd">
  <configuration>
      <!-- 加载外部配置文件 -->
      <properties resource="jdbc.properties"></properties>
      <settings>
      <!--开启驼峰命名法-->
         <setting name="mapUnderscoreToCamelCase" value="true"/>
     </settings>
     
     <!-- 起别名 -->
     <typeAliases>
       <typeAlias alias="User" type="cn.mybatis.pojo.User"/>
     </typeAliases>
 
   <environments default="development">
     <environment id="development">
       <transactionManager type="JDBC"/>
       <dataSource type="POOLED">
         <property name="driver" value="${jdbc.driver}"/>
         <property name="url" value="${jdbc.url}"/>
         <property name="username" value="${jdbc.username}"/>
         <property name="password" value="${jdbc.password}"/>
       </dataSource>
     </environment>
   </environments>
   
   <!-- 指定mapper的配置文件 -->
   <mappers>
     <mapper resource="mapper.xml"/>
     <mapper resource="usermapper.xml"/>
   </mappers>
 </configuration>

3.编写映射配置文件

<?xml version="1.0" encoding="UTF-8" ?>
  <!DOCTYPE mapper
    PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
    "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
  <mapper namespace="cn.mapper.UserMapper">
  
    <select id="queryUserById" parameterType="java.lang.Long"  resultType="User">
      select * from tb_user where id = #{id}
    </select>
   
   <select id="queryAll"  resultType="User">
     select * from tb_user
   </select>
   
   <insert id="insertUser" parameterType="User">
     INSERT INTO tb_user (
                 id,
                 user_name,
                 password,
                 name,
                 age,
                 sex,
                 birthday,
                 created,
                 updated
             )VALUES(
                 null,
                 #{userName},
                 #{password},
                 #{name},
                 #{age},
                 #{sex},
                 #{birthday},
                 NOW(),
                 NOW()
             );
   </insert>   
   <delete id="deleteById" parameterType="Long">
           DELETE FROM tb_user WHERE id = #{id}
   </delete>      
 </mapper>

4.编写测试类

 package cn.mybatis.junit.test;
  
 import static org.junit.Assert.*;
  
 import java.io.InputStream;
 import java.util.List;
  
 import org.apache.ibatis.io.Resources;
 import org.apache.ibatis.session.SqlSession;
 import org.apache.ibatis.session.SqlSessionFactory;
 import org.apache.ibatis.session.SqlSessionFactoryBuilder;
 import org.junit.Before;
 import org.junit.Test;
 
 public class UserMapperTest {
 
     private UserMapper userMapper;
     
     InputStream inputStream;
     SqlSessionFactory sqlSessionFactory;
     SqlSession sqlSession;
     
     @Before
     public void setUp() throws Exception {
         
         String resource = "mybatis-config.xml";
         
         
         inputStream = Resources.getResourceAsStream(resource);
         
         sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
         
         sqlSession = sqlSessionFactory.openSession();
         
 //        通过动态代理获取
         userMapper = sqlSession.getMapper(UserMapper.class);
         
     }
 
     /**
      * 根据id查询
      */
     @Test
     public void test() {
         User user = userMapper.queryUserById(1L);
         System.out.println(user);
     }
     /**
      * 查询全部
      */
     @Test
     public void test1() {
         List<User> all = userMapper.queryAll();
         
         for (User user2 : all) {
             System.out.println(user2);
         }
     }
     
     /**
      * 插入用户
      */
     @Test
     public void test2() {
         User user = new User();
         user.setAge(22);
         user.setBirthday(null);
         user.setName("jack");
         user.setPassword("123");
         user.setSex(1);
         user.setuserName("pick jack");
         
         userMapper.insertUser(user);
         
         this.sqlSession.commit();
     }
     
     /**
      * 删除
      */
     @Test
     public void test3() {
         this.userMapper.deleteById(12L);
         
         this.sqlSession.commit();
     }
 }