05-mybatis-分页

1.分页的目的

减少数据量

2.分页的方法有几种

• 2.1   第一种：limit分页       sqly语句：select * from user limit(起始下标，每页显示个数)

与Mybatis结合步骤：

创建接口

 //分页
    List<User> getUserByLimit(Map<String,Integer> map);

创建mapper.xml

<mapper namespace="com.neusoft.dao.UserMapper">
    <resultMap id="UserMap" type="User">
        <result column="name" property="username"/>
    </resultMap>
    <select id="getUserByLimit" parameterType="map" resultMap="UserMap">
        select id,name,password,email from users limit #{startIndex},#{pageSize}
    </select>
</mapper>

测试

@Test
    public void test1(){
        SqlSession sqlSession=MybatisUtils.getSqlSession();
        UserMapper mapper=sqlSession.getMapper(UserMapper.class);
        Map<String,Integer> map=new HashMap<String ,Integer>();
        map.put("startIndex",1);
        map.put("pageSize",2);
        List<User> list= mapper.getUserByLimit(map);
        for (User u:list) {
            System.out.println(u);
        }
        sqlSession.close();
    }

• 2.2   第二种：RowBounds类

创建接口

//RowBounds分页
    List<User> getUserByRowBounds();

创建mapper.xml

<select id="getUserByRowBounds" resultMap="UserMap">
        select id,name,password,email from users
    </select>

测试

 @Test
    public void test2(){
        SqlSession sqlSession=MybatisUtils.getSqlSession();
        RowBounds rowBounds=new RowBounds(1,2);
        List<User> userList= sqlSession.selectList("com.neusoft.dao.UserMapper.getUserByRowBounds",null,rowBounds);
        for (User user : userList) {
            System.out.println(user);
        }
        sqlSession.close();
    }

2.3   第三种Mybatis分页插件   pageHelper