Mybatis实现增删查改

接上篇：Mybatis入门

这里的所有测试没有使用注解

1. 查询

上篇使用了查询语句

<mapper namespace="cn.sjcup.Mapper.UserMapper">
    <select id="getUserList" resultType="cn.sjcup.pojo.User">
        select * from mybatis.user
    select>
mapper>

• namespace中的包名要和mapper接口的包名一致
• id：对应的namespace的方法名
• resultType：sql语句执行的返回值类型
• parameterType：参数类型

根据id查询用户

增加了一个需求，在本示例中，只需要修改三处代码，对应三步操作：1.编写接口；2.编写mapper中的sql语句；3.测试

UserMapper

public interface UserMapper {
    //查询全部用户
    List<User> getUserList();

    //根据id查询用户
    User getUserById(int id);
}

UserMapper.xml

<select id="getUserById" parameterType="int" resultType="cn.sjcup.pojo.User">
    select * from mybatis.user where id =#{id}
select>

Test

@Test
public void getUserById(){

    //1.获取sqlSession对象
    SqlSession sqlSession = MybatisUtils.getSqlSession();
    //2.执行sql
    UserMapper mapper = sqlSession.getMapper(UserMapper.class);
    User user1 = mapper.getUserById(1);

    System.out.println(user1);

    //3.关闭sqlsession
    sqlSession.close();
}

输出结果：

> User{id=1, name='张三', pwd='123456'}

2. 插入

增、删、改需要添加事务的提交

UserMapper

//插入一个用户
int addUser(User user);

UserMapper.xml

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

Test

//增删改需要提交事务
@Test
public void addUser(){
    //1.获取sqlSession对象
    SqlSession sqlSession = MybatisUtils.getSqlSession();
    //2.执行sql
    UserMapper mapper = sqlSession.getMapper(UserMapper.class);
    int result = mapper.addUser(new User(4, "小明", "124578"));

    //3. 提交事务
    sqlSession.commit();

    //4.关闭sqlsession
    sqlSession.close();
}

3. 修改

UserMapper

//修改一个用户
int updateUser(User user);

UserMapper.xml

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

Test

@Test
public void updateUser(){
    //1.获取sqlSession对象
    SqlSession sqlSession = MybatisUtils.getSqlSession();
    //2.执行sql
    UserMapper mapper = sqlSession.getMapper(UserMapper.class);
    mapper.updateUser(new User(2, "小红", "789"));

    //3. 提交事务
    sqlSession.commit();

    //4.关闭sqlsession
    sqlSession.close();
}

4. 删除

UserMapper

//删除一个用户
int deleteUser(int id);

UserMapper.xml

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

Test

@Test
public void deleteUser(){
    //1.获取sqlSession对象
    SqlSession sqlSession = MybatisUtils.getSqlSession();
    //2.执行sql
    UserMapper mapper = sqlSession.getMapper(UserMapper.class);
    mapper.deleteUser(4);

    //3. 提交事务
    sqlSession.commit();

    //4.关闭sqlsession
    sqlSession.close();
}

5. map

在上述增删查改的测试中，使用到了User类，这些也可以使用map，相比而言，使用map更加灵活，但也后期维护需要了解每个参数代表的含义，增加了维护成本。

修改

UserMapper

int updateUser2(Map<String, Object> map);

UserMapper.xml

<update id="updateUser2" parameterType="map">
    update mybatis.user set pwd=#{password}  where id=#{id};
update>

Test

//测试map
@Test
public void updateUser2(){
    //1.获取sqlSession对象
    SqlSession sqlSession = MybatisUtils.getSqlSession();
    //2.执行sql
    UserMapper mapper = sqlSession.getMapper(UserMapper.class);

    Map<String, Object> map = new HashMap<String, Object>();
    map.put("id", 2);
    map.put("password", 11111);

    mapper.updateUser2(map);

    //3. 提交事务
    sqlSession.commit();

    //4.关闭sqlsession
    sqlSession.close();
}