Mybatis之Mapper动态代理方式

mybatis属于持久层框架，用它来写dao层开发者只需要编写mapper接口，由Mybatis框架根据接口定义创建接口的动态代理对象。

实体类User

public class User implements Serializable {    private Integer id;    private String username;    private String password;    private Date birthday;    private String address;    public User() {    }    public User(String username, String password, Date birthday, String address) {        this.username = username;        this.password = password;        this.birthday = birthday;        this.address = address;    }    get、set、toString方法}

sql映射文件User.xml中使用上一篇博文mybatis快速入门
中已经写好的，如下：

<?xml version="1.0" encoding="UTF-8" ?><!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd"><!-- namespace：命名空间，用于隔离sql，名称要写对应的mapper接口全路径名 --><!-- 写sql语句 --><mapper namespace="com.scu.mybatis.mapper.UserMapper">    <!-- 插入数据 -->    <insert id="save" parameterType="com.scu.mybatis.entity.User">    <selectKey keyProperty="id" order="AFTER" resultType="int">        SELECT LAST_INSERT_ID()    </selectKey>        INSERT INTO t_user (username,password,birthday,address) VALUES(#{username},#{password},#{birthday},#{address})    </insert>    <!-- 根据id查询数据 -->    <select id="findById" parameterType="int" resultType="com.scu.mybatis.entity.User">        SELECT * FROM t_user u WHERE u.id=#{id}     </select>    <!-- 查询所有用户信息 -->    <select id="findList" resultType="com.scu.mybatis.entity.User">        SELECT * FROM t_user    </select>    <!-- 根据用户名模糊查询,一定要写成value不能写成username -->    <select id="findByName" resultType="com.scu.mybatis.entity.User" parameterType="string">        SELECT * FROM t_user u WHERE u.username LIKE '%${value}%'     </select>    <!-- 修改用户信息 -->    <update id="updateById" parameterType="com.scu.mybatis.entity.User">        UPDATE t_user u SET u.username=#{username},u.password=#{password},            u.birthday=#{birthday},u.address=#{address}        WHERE u.id=#{id}     </update>    <!-- 删除 -->    <deleteid="delete" parameterType="int">        DELETE FROM t_user  WHERE id=#{id}     </delete></mapper>

mapper接口
创建对应于User.xml的mapper接口UserMapper
Mapper接口开发需要遵循以下规范：

1. 方法名要与User.xml中id一致；
2. 返回参数类型要与User.xml中对应语句的返回参数类型(resultType)一致；
3. 形参类型要与 User.xml中对应语句的入参（parameterType）类型一致；
4. 另外，User.xml文件中的namespace要写UserMapper接口的完整路径名。

UserMapper接口如下

public interface UserMapper {    //插入数据    public void save(User user);    //根据id查询数据     public User findById(int id);    //查询所有用户信息    public List<User> findList();    //根据用户名模糊查询    public List<User> findByName(String username);    //修改用户信息    public void updateById(User user);    //删除用户    public void delete(int id);}

分别测试上面6个方法：
1、创建SqlSessionFactoryBuilder；
2、获取SqlSessionFactory；
3、获取SqlSession；
4、获取UserMapper；
5、执行方法；
6、关闭SqlSession和输入流；

/** * 测试Mapper中的crud * @author 12706 * */public class UserMapperTest {    InputStream inputStream;    SqlSession session;    @Before    public void init() throws Exception{        String resource = "sqlMapConfig.xml";        inputStream = Resources.getResourceAsStream(resource);        SqlSessionFactoryBuilder ssfb = new SqlSessionFactoryBuilder();        SqlSessionFactory sqlSessionFactory = ssfb.build(inputStream);        session = sqlSessionFactory.openSession();    }    @After    public void destroy() throws Exception{        inputStream.close();        session.close();    }    @Test    /*     * 添加用户信息     */    public void testSave(){        User user = new User("小雨", "123456", new Date(), "安徽池州市");        //获取Mapper        UserMapper mapper = session.getMapper(UserMapper.class);        //添加用户信息        mapper.save(user);        System.out.println(user.getId());        session.commit();    }}

添加用户后查看数据库t_user表,用户信息成功添加，并且控制台输出了3（新添加的用户id）：

剩下的方法测试结果就不展示了

@Test    /*     * 获取单个对象     */    public void testFindById(){        //获取Mapper        UserMapper mapper = session.getMapper(UserMapper.class);        //根据id查询用户信息        User user = mapper.findById(2);        System.out.println(user);    }    @Test    /*     * 获取对象集合     */    public void testFindList(){        //获取Mapper        UserMapper mapper = session.getMapper(UserMapper.class);        //查询用户列表        List<User> list = mapper.findList();        for (User user : list) {            System.out.println(user);        }    }    @Test    /*     * 模糊查询     */    public void testFindByName(){        //获取Mapper        UserMapper mapper = session.getMapper(UserMapper.class);        //用户名模糊查询用户列表        List<User> list = mapper.findByName("张");        for (User user : list) {            System.out.println(user);        }    }    @Test    /*     * 修改用户信息     */    public void testUpdate(){        //获取Mapper        UserMapper mapper = session.getMapper(UserMapper.class);        User user = mapper.findById(2);        user.setUsername("小红");        user.setAddress("四川省成都市武侯区");        //更新id为2的用户信息        mapper.updateById(user);        session.commit();    }    @Test    /*     * 删除用户信息     */    public void testDelete(){        //获取Mapper        UserMapper mapper = session.getMapper(UserMapper.class);        mapper.delete(2);        session.commit();    }