[Java知识库]MyBatis分页、注解开发

分页

limit分页：

SELECT * from user limit startIndex,pageSize;

Mybatis分页，基于SQL

1.接口

List<User> getUserByLimit(Map<String, Object> map);

2.mapper

    <select id="getUserByLimit" parameterType="map" resultType="user">
        select * from user limit #{startIndex},#{pageSize}
    </select>

3.测试

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

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

        HashMap<String, Object> map = new HashMap<>();
        map.put("startIndex", 2);
        map.put("pageSize", 2);

        List<User> userByLimit = mapper.getUserByLimit(map);
        for (User user : userByLimit) {
            System.out.println(user);
        }
        sqlSession.close();
    }

RowBounds分页

不再基于SQL，基于JAVA对象实现
1.接口

List<User> getUserByRowBounce(Map<String, Object> map);

2.mapper

    <select id="getUserByRowBounce" resultType="user">
        select * from user
    </select>

3.测试使用：

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

        RowBounds rowBounds = new RowBounds(1, 2);

        List<User> objects = sqlSession.selectList("com.lms.dao.UserMapper.getUserByRowBounce", null, rowBounds);

        for (User object : objects) {
            System.out.println(object);
        }

        sqlSession.close();
    }

注解开发

核心使用反射进行底层实现。
1.注解在接口上实现

    @Select("select * from user")
    List<User> getUsers();

2.核心配置文件绑定

    <mappers>
        <mapper class="com.lms.dao.UserMapper"/>
    </mappers>

3.测试

本质：反射机制
底层：动态代理

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