Mybatis分页查询同时查询数据和总数量

分页查询时，一次性查询分页数据和总数量，而不是分两次查询。

1,Mapper.xml文件配置

    <resultMap id="beanMap" type="com.gx.pojo.DeptVo">
        <result column="deptNo" property="deptNo"></result>
        <result column="deptName" property="deptName"></result>
    </resultMap>
    <resultMap id="count" type="java.lang.Integer">
        <result column="total"/>
    </resultMap>
    <select id="getAll" parameterType="java.util.Map" resultMap="beanMap,count">
        select SQL_CALC_FOUND_ROWS * from dept order by deptNo limit #{pageStart},#{pageSize};
        select FOUND_ROWS() as total;
    </select>

sql语句上使用SQL_CALC_FOUND_ROWS和SELECT FOUND_ROWS AS total，可以查询数据列表的同时查询总数。

2,Dao代码

public interface DeptMapper {
    List<Object> getAll(Map<String,Object> map);
}

3，测试

    @Test
    public void getDeptList(){

        DeptMapper mapper = sqlSession.getMapper(DeptMapper.class);
        Map<String,Object> map=new HashMap<>();
        map.put("pageStart",0);
        map.put("pageSize",3);
        List<Object> all = mapper.getAll(map);
        List<DeptVo> list =(List<DeptVo>) all.get(0);
        Integer total =(Integer)((List<Object>)all.get(1)).get(0);
        list.forEach(System.out::println);
        System.out.println(total);
        sqlSession.close();
    }

3，需要注意的是在mysql连接字符串url上需配置allowMultiQueries=true