SSM框架学习之路-Mybatis（七）分页

程序员文章站 2022-07-12 22:30:44

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7、分页

**思考：**为什么要使用分页？

减少数据处理量

使用Limit分页

-- 语法： select * from mybatis.user limit startIndex, pageSize;
select * from mybatis.user limit 3; -- [0, n]

使用Mybatis分页，核心SQL

接口

// 分页获取用户
public List<User> getUserByLimit(Map<String, Integer> map);

Mapper.xml

<!--分页-->
<select id="getU serByLimit" parameterType="map" resultMap="userMap">
    select * from mybatis.user limit #{startIndex}, #{pageSize}
</select>

测试

@Test
public void getUserByLimit() {
    SqlSession sqlSession = MybatisUtils.getSqlSession();
    UserMapper mapper = sqlSession.getMapper(UserMapper.class);
    Map<String, Integer> map = new HashMap<String, Integer>();
    map.put("startIndex", 0);
    map.put("pageSize", 2);
    List<User> userList = mapper.getUserByLimit(map);
    for (User user : userList) {
        System.out.println(user);
    }
    sqlSession.close();
}

7.2、RowBounds分页

不再使用SQL实现分页

接口

// 分页2
public List<User> getUserByRowBounds();

Mapper.xml

<!--分页2-->
<select id="getUserByRowBounds" resultMap="userMap">
    select * from mybatis.user
</select>

测试

@Test
public void getUserByRowBounds() {
    SqlSession sqlSession = MybatisUtils.getSqlSession();
    // RowBounds实现
    RowBounds rowBounds = new RowBounds(1, 2);
    // 通过java代码层实现分页
    List<User> users = sqlSession.selectList("com.wsw.dao.UserMapper.getUserByRowBounds", null, rowBounds);
    for (User user : users) {
        System.out.println(user);
    }
    sqlSession.close();
}