关于mybatis:Mybatis入门之CRUD

xml 元素

• namespace
  xml 中的 namespace 与 dao 接口的包名统一
• id
  xml 中的 id 与 dao 接口的办法名统一
• resultType
  sql 语句执行的返回值
• parameterType
  参数类型

select

1. 编写接口

// 查问全副用户
List<User> getUserList();

2. 编写 sql 语句

<!--select 查问语句 -->
<select id="getUserList" resultType="com.sunfl.pojo.User">
    select * from mybatis.user
</select>

3. 测试

@Test
public void test(){
    // 取得 SqlSession 对象
    SqlSession sqlSession = MybatisUtils.getSqlSession();
    // 形式一：执行 SQL  举荐
    UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
    List<User> userList = userMapper.getUserList();

    // 形式二：//        List<User> userList = sqlSession.selectList("com.sunfl.dao.UserDao.getUserList");

    for (User user : userList) {System.out.println(user);
    }

    // 敞开 sqlSession
    sqlSession.close();}

insert

1. 编写接口

// 新增一个用户
int addUser(User user);

2. 编写 sql 语句

<insert id="addUser" parameterType="com.sunfl.pojo.User">
    insert into mybatis.user (id, name, pwd) values (#{id},#{name},#{pwd});
</insert>

3. 测试

@Test
public void addUser(){SqlSession sqlSession = MybatisUtils.getSqlSession();

    UserMapper mapper = sqlSession.getMapper(UserMapper.class);

    mapper.addUser(new User(4, "哈哈哈", "12323"));
    sqlSession.commit();
    sqlSession.close();}

update

1. 编写接口

// 更新一个用户
int updateUser(User user);

2. 编写 sql 语句

<update id="updateUser" parameterType="com.sunfl.pojo.User">
    update mybatis.user set name=#{name},pwd=#{pwd} where id=#{id};
</update>

3. 测试

@Test
public void updateUser(){SqlSession sqlSession = MybatisUtils.getSqlSession();

    UserMapper mapper = sqlSession.getMapper(UserMapper.class);

    mapper.updateUser(new User(4,"嘿嘿","1111"));
    sqlSession.commit();
    sqlSession.close();}

delete

1. 编写接口

// 删除一个用户
int deleteUser(int id);

2. 编写 sql 语句

<delete id="deleteUser" parameterType="int">
    delete from mybatis.user where id = #{id};
</delete>

3. 测试

@Test
public void deleteUser(){SqlSession sqlSession = MybatisUtils.getSqlSession();

    UserMapper mapper = sqlSession.getMapper(UserMapper.class);

    mapper.deleteUser(4);
    sqlSession.commit();
    sqlSession.close();}