Mybatis Dao开发方法（二）

使用Mapper代理的方式进行开发

Mapper开发的原理

  使用Mybatis的Mapper代理方式进行开发，使用该方式，只需要编写Mapper接口，不再需要编写实现类，由Mybatis框架通过接口定义来自动生成接口的动态代理对象。

Mapper代理开发要遵循的原则

  1. Mapper.xml文件中的namespace要和Mapper接口的类路径相同。
  2. Mapper接口中的方法名称要和Mapper.xml中定义的每个statement的id相同。
  3. Mapper接口的输入参数类型要和Mapper.xml文件中定义的相对应sql的parameterType的类型相同。
  4. Mapper接口的输出参数类型要和Mapper.xml文件中定义的相对应的sql的resultType的类型相同。

Mapper代理开发过程

 1. 创建UserMapper.xml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">
<!--namespace：Mapper接口类的路径-->
<mapper namespace="com.jack.dao.UserMapper">
    <!--根据id查询用户-->
    <select id="findUserById" parameterType="int" resultType="User">
        SELECT * FROM user WHERE id=#{id}
    </select>
    <!--根据用户名模糊查询用户信息-->
    <select id="findUserByName" parameterType="String" resultType="User" >
        SELECT * FROM user WHERE username LIKE '%${value}%'
    </select>
    <!--插入用户信息-->
    <insert id="addUser" parameterType="User">
        <selectKey keyProperty="id" order="AFTER" resultType="Integer">
            SELECT LAST_INSERT_ID()
        </selectKey>
        INSERT INTO user(username,birthday,sex,address) VALUE (#{username},#{birthday},#{sex},#{address})
    </insert>
    <!--根据id修改用户信息-->
    <update id="updateUserById" parameterType="User">
        UPDATE user SET username=#{username},birthday=#{birthday},sex=#{sex},address=#{address} WHERE id=#{id}
    </update>
    <!--根据id删除用户信息-->
    <delete id="deleteUserById" parameterType="int">
        DELETE FROM user WHERE id=#{value}
    </delete>
    </mapper>

 2、编写UserMapper接口文件

public interface UserMapper {
                //根据id查询用户信息
               public User findUserById(int id) throws Exception;
                //根据用户名查询用户
                public List<User> findUserByName(String name) throws Exception;
                //插入用户信息
                public int addUser(User user) throws Exception;
                //根据id修改用户信息
                public  void updateUserById(User user) throws Exception;
                //根据id删除用户信息
                public void deleteUserById(int id) throws Exception;
            }

 3、编写测试代码

public class UserTest {

    public SqlSessionFactory sessionFactory;
    public  SqlSession sqlSession;
    public SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd");

    @Before
    public void setUp() throws IOException {
        String resource = "SqlMapConfig.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        sessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    }

    @Test
    public void findUserById(){
        try {
             sqlSession = sessionFactory.openSession();
            UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
            User user = userMapper.findUserById(1);
            System.out.println("查询成功，信息如下:");
            if(user.getBirthday() != null){
                simpleDateFormat.format(user.getBirthday());
            }
            System.out.println(user);
        }catch (Exception e){
            System.out.println("查询失败");
        }finally {
            sqlSession.close();
        }
    }

    @Test
    public void findUserByName(){
        try {
            sqlSession = sessionFactory.openSession();
            UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
            List<User> list = userMapper.findUserByName("小明");

            System.out.println("查询成功，信息如下:");
            for (User user: list) {
                if(user.getBirthday() != null){
                    simpleDateFormat.format(user.getBirthday());
                }
                System.out.println(user);
            }
        }catch (Exception e){
            System.out.println("查询失败");
        }finally {
            sqlSession.close();
        }
    }

    @Test
    public void addUser(){
        try {
            sqlSession = sessionFactory.openSession();
            UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
            User user = new User();
            user.setUsername("小布");
            user.setBirthday(new Date());
            user.setSex("1");
            user.setAddress("湖北 十堰");
           int id = userMapper.addUser(user);
            System.out.println("插入成功，新插入的用户id为:"+user.getId());
           sqlSession.commit();

        }catch (Exception e){
            System.out.println("插入失败");
        }finally {
            sqlSession.close();
        }
    }

    @Test
    public void updateUserById(){
        try {
            sqlSession = sessionFactory.openSession();
            UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
            User user = new User();
            user.setId(4);
            user.setUsername("小布");
            user.setBirthday(new Date());
            user.setSex("0");
            user.setAddress("湖北 十堰");
            userMapper.updateUserById(user);
            sqlSession.commit();
            System.out.println("id为"+user.getId()+"的用户信息更新成功");
        }catch (Exception e){
            System.out.println("更新失败");
        }finally {
            sqlSession.close();
        }
    }

    @Test
    public void deleteUserById(){
        try {
            sqlSession = sessionFactory.openSession();
            UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
            userMapper.deleteUserById(3);
            sqlSession.commit();
            System.out.println("删除成功");

        }catch (Exception e){
            System.out.println("更新失败");
        }finally {
            sqlSession.close();
        }
    }

其余步骤和原生Dao开发相同

来源：https://www.cnblogs.com/jack1995/p/7242855.html