Mybatis入门笔记(1)——基于原始dao实现CRUD

基于原始dao实现CRUD

需要程序员编写Dao接口和Dao实现类，即就是UserDao接口和UserDaoImpl实现类

原始Dao开发中存在以下问题：

• Dao方法体存在重复代码：通过SqlSessionFactory创建SqlSession，调用SqlSession的数据库操作方法
• 调用sqlSession的数据库操作方法需要指定statement的id，这里存在硬编码，不得于开发维护。

项目结构：

持久层dao接口

UserDao.java

public interface UserDao{
    // 通过ID查询一个用户
    public User findUserById(Integer id);
    // 根据用户名模糊查询用户列表
    public List<User> findUserByUserName(String userName);
    // 添加用户
    public int insertUser(User user);
    // 更新用户
    public void updateUserById(User user);
    // 删除用户
    public void deleteUserById(Integer id);
}

持久层dao接口实现类

UserDaoImpl.java

/**
 * @ClassName: 持久层实现类
 * @author: benjamin
 * @createTime: 2019/07/14/20:22
 */
public class UserDaoImpl implements UserDao{

    private SqlSessionFactory sqlSessionFactory;

    // 通过构造方法注入
    public UserDaoImpl(SqlSessionFactory sqlSessionFactory){
        this.sqlSessionFactory = sqlSessionFactory;
    }


    public User findUserById(Integer id) {
        //sqlSession是线程不安全的，所以它的最佳使用范围在方法体内
        SqlSession sqlSession = sqlSessionFactory.openSession();
        User user = sqlSession.selectOne("test.findUserById",id);
        sqlSession.close();
        return user;
    }

    public List<User> findUserByUserName(String userName) {
        SqlSession sqlSession = sqlSessionFactory.openSession();
        List<User> list = sqlSession.selectList("test.findUserByUsername", userName);
        sqlSession.close();
        return list;
    }
    // 插入用户
    public int insertUser(User user){
        SqlSession sqlSession = sqlSessionFactory.openSession();
        int res = sqlSession.insert("test.insertUser", user);
        sqlSession.commit();
        sqlSession.close();
        return res;
    }

    // 更新用户
    public void updateUserById(User user){
        SqlSession sqlSession = sqlSessionFactory.openSession();
        sqlSession.update("test.updateUserById",user);
        sqlSession.commit();
        sqlSession.close();
    }
    // 删除用户
    public void deleteUserById(Integer id){
        SqlSession sqlSession = sqlSessionFactory.openSession();
        sqlSession.delete("test.deleteUserById",id);
        sqlSession.commit();
        sqlSession.close();
    }
}

持久层映射

<?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：用来区别不同的类的名字 -->
<mapper namespace="test">

    <!-- 通过Id查询一个用户   -->
    <select id="findUserById" parameterType="Integer" resultType="com.ben.domain.User">
        select * from user where id = #{v}
    </select>

    <!-- 根据用户名模糊查询用户列表 -->
    <!--    select * from user where username like '%${value}%'-->
<!-- select * from user where username like "%"#{value}"%"-->
    <select id="findUserByUsername" parameterType="String" resultType="com.ben.domain.User">
        select * from user where username like "%"#{value}"%"
    </select>
    <!--  添加用户  -->
    <insert id="insertUser" parameterType="com.ben.domain.User">
        <selectKey keyProperty="id" resultType="Integer" order="AFTER">
            select LAST_INSERT_ID()
        </selectKey>
        insert into user (username,birthday,address,sex) values(#{username},#{birthday},#{address},#{sex})
    </insert>
    <!-- 更新用户 -->
    <update id="updateUserById" parameterType="com.ben.domain.User">
		update user
		set username = #{username},sex = #{sex},birthday = #{birthday},address = #{address}
		where id = #{id}
	</update>
    <!-- 删除用户   -->
    <delete id="deleteUserById" parameterType="Integer">
		delete from user
		where id = #{vvvvv}
	</delete>
</mapper>

测试类

UserDaoTest.java

/**
 * @ClassName: UserDaoTest
 * @author: benjamin
 * @version: 1.0
 * @description: TODO
 * @createTime: 2019/07/14/20:38
 */

public class UserDaoTest {
    
    private SqlSessionFactory factory;
    private UserDao userdao;
    private InputStream in;
    // 作用：在测试方法前执行这个方法
    @Before
    public void setUp() throws Exception{
        //1.读取配置文件
        in = Resources.getResourceAsStream("SqlMapConfig.xml");
        //2.创建SqlSessionFactory工厂
        factory = new SqlSessionFactoryBuilder().build(in);
    }

    @After//在测试方法执行完成之后执行
    public void destroy() throws IOException {
        in.close();
    }
    //通过Id查询一个用户
    @Test
    public void testFindUserById() throws Exception{
        // 将初始化好的工厂注入到实现类中
        UserDao userdao = new UserDaoImpl(factory);
        User user = userdao.findUserById(34);
        System.out.println(user);
        //User [id=34, username=小小, sex=1, birthday=Mon Jul 15 00:00:00 CST 2019, address=西安市]
    }

    //根据用户名模糊查询用户列表
    @Test
    public void testFindUserByUserName() throws Exception{
        UserDao userdao = new UserDaoImpl(factory);
        List<User> list = userdao.findUserByUserName("王");
        for (User user:list) {
            System.out.println(user);
        }
    }
    //添加用户
    @Test
    public void testInsertUser() throws IOException {
        UserDao userdao = new UserDaoImpl(factory);
        User user = new User();
        user.setUsername("小王");
        user.setBirthday(new Date());
        user.setAddress("sadfsafsafs");
        user.setSex("2");
        int i = userdao.insertUser(user);

        System.out.println("插入id:"+user.getId());//插入id:35
    }
    //更新用户
    @Test
    public void testUpdateUserById() throws IOException {
        UserDao userdao = new UserDaoImpl(factory);

        User user = new User();
        user.setId(35);
        user.setUsername("小小");
        user.setBirthday(new Date());
        user.setAddress("西安市");
        user.setSex("1");
        userdao.updateUserById(user);

        System.out.println(user.getId());
    }
    //删除用户
    @Test
    public void testDeleteUserById() throws IOException {
        UserDao userdao = new UserDaoImpl(factory);
        userdao.deleteUserById(34);
    }
}