Mybatis学习总结第二篇

2024-02-11 18:36:40

Mybatis学习总结第二篇

一、在pom.xml中导入相关依赖

mysql-connector-java
mybatis
junit

二、编写MyBatis配置文件

<configuration>
    <!-- 配置环境：可以配置多个环境，default：配置某一个环境的唯一标识，表示默认使用哪个环境 -->
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <!-- 配置连接信息 -->
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis?characterEncoding=utf-8"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>
    <!-- 配置映射文件：用来配置sql语句和结果集类型等 -->
    <!--每一个Mapper.xml文件都需要在Mybatis核心配置文件中注册-->
    <mappers>
        <mapper resource="mapper/UserMapper.xml"/>
    </mappers>
</configuration>

三、编写工具类MybatisUtils

public class MybatisUtils {
    private static SqlSessionFactory sqlSessionFactory;
    static{
        try {
            //第一步：使用Mybatis获取sqlSessionFactory对象
            String resource = "mybatis-config.xml";
            //创建流
            InputStream inputStream = Resources.getResourceAsStream(resource);
            //加载流
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    //第二步：获取SqlSession实例
    public static SqlSession getSqlSession(){
        return sqlSessionFactory.openSession();
    }
}

四、编写User实体类

有参构造、无参构造、get\set方法以及toString方法省略…

private int id;
private String username;
private String password;
private String sex;
private String address;

五、编写UserMapper接口

查询所有用户
根据id查询用户
添加用户
修改用户
删除用户

public interface UserMapper {
    //查询所有用户
    List<User> getUserList();
    //根据id查询用户(返回值为User)
    User getUserById(int id);
    //添加用户
    int addUser(User user);
    //修改用户
    int updateUser(User user);
    //删除用户
    int deleteUser(int id);

}

六、编写映射文件

注意：要在配置文件中加载映射文件

<mapper namespace="com.dmj.dao.UserMapper">
    <!--id对应Mapper中的方法名字-->
    <select id="getUserList" resultType="com.dmj.entity.User">
       select * from mybatis.user1
    </select>
    
    <!--根据id查询用户-->
    <select id="getUserById" resultType="com.dmj.entity.User">
        select * from mybatis.user1 where id = #{id}
    </select>
    
    <!--添加用户-->
    <insert id="addUser" parameterType="com.dmj.entity.User">
        insert into mybatis.user1 (id, username, password, sex,address) values (#{id},#{username},#{password},#{sex},#{address})
    </insert>
    
    <!--修改用户-->
    <update id="updateUser" parameterType="com.dmj.entity.User">
        update mybatis.user1 set username = #{username},password = #{password},sex = #{sex},address= #{address} where id = #{id} ;
    </update>
    
    <!--删除用户-->
    <delete id="deleteUser" parameterType="com.dmj.entity.User">
        delete from mybatis.user1 where id = #{id}
    </delete>
</mapper>

七、测试（实现增删改查操作）

注意：增删改需要提交事务 sqlSession.commit();

public class UserDaoTest {
    @Test
    //查询所有用户
   public  void test(){
       //获得SqlSession对象
        SqlSession sqlSession = MybatisUtils.getSqlSession();
       //方式一：getMapper(推荐使用)
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List<User> userList = mapper.getUserList();

        //方式二：
        //List<User> userList = sqlSession.selectList("com.dmj.dao.UserMapper.getUserList");
        for (User user : userList) {
            System.out.println(user);
        }
        sqlSession.close();//关闭
   }

   //通过id查询用户
   @Test
   public void getUserById(){
       SqlSession sqlSession = MybatisUtils.getSqlSession();
       UserMapper mapper = sqlSession.getMapper(UserMapper.class);
       User user = mapper.getUserById(2);
       System.out.println(user);
       sqlSession.close();
   }

   //添加用户
    @Test
    public void addUser(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();

        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        int res = mapper.addUser(new User(3,"王五","123456","男","浙江丽水"));
        if (res>0){
            System.out.println("添加成功！");
        }
        //提交事务
        sqlSession.commit();
        sqlSession.close();
    }

    //修改用户
    @Test
    public void updateUser(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        int res = mapper.updateUser(new User(3,"哈哈","654321","女","浙江金华"));
        if (res>0){
            System.out.println("修改成功！");
        }
        //提交事务
        sqlSession.commit();
        sqlSession.close();
    }

    //删除用户
    @Test
    public void deleteUser(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        int res = mapper.deleteUser(3);
        if (res>0){
            System.out.println("删除成功！");
        }
        //提交事务
        sqlSession.commit();
        sqlSession.close();
    }
}