前言
在使用Mybatis时，最头痛的就是写分页了，需要先写一个查询count的select语句，然后再写一个真正分页查询的语句，当查询条件多了之后，会发现真的不想花双倍的时间写 count 和 select，幸好我们有 pagehelper 分页插件，pagehelper 是一个强大实用的 MyBatis 分页插件，可以帮助我们快速的实现MyBatis分页功能，而且pagehelper有个优点是，分页和Mapper.xml完全解耦，并以插件的形式实现，对Mybatis执行的流程进行了强化，这有效的避免了我们需要直接写分页SQL语句来实现分页功能。
现在我把自己在项目中实现分页的方法总结如下：
1.导入Maven依赖
<!--分页插件-->
<!-- https://mvnrepository.com/artifact/com.github.pagehelper/pagehelper-spring-boot-starter -->
<dependency>
<groupId>com.github.pagehelper</groupId>
<artifactId>pagehelper-spring-boot-starter</artifactId>
<version>1.3.0</version>
</dependency>
2.controller中分页方法
/**
* @Description: 分页查询
* @Param: waterloggingPreventionDto
* @return com.graphsafe.api.msg.RestMessage(封装的返回值信息)
* @author songwp
* @date 2021/11/2 15:00
*/
@PostMapping(value = "getListForPage", produces = "application/json;charset=UTF-8")
public RestMessage getListForPage(@RequestBody WaterloggingPreventionDto waterloggingPreventionDto){
WaterloggingPreventionVo result = new WaterloggingPreventionVo();
List<WaterloggingPrevention> list = waterloggingPreventionService.getListForPage(waterloggingPreventionDto);
result.setWaterloggingPreventionList(list);
if (null != waterloggingPreventionDto.getCount()){
result.setTotal(waterloggingPreventionDto.getCount().intValue());
}
return new RestMessage(result);
}
3.service业务方法的实现
@Override
public List<WaterloggingPrevention> getListForPage(WaterloggingPreventionDto waterloggingPreventionDto) {
List<WaterloggingPrevention> list = new ArrayList<>();
if (waterloggingPreventionDto.getPage() != null && waterloggingPreventionDto.getLimit() != null){
PageHelper.startPage(waterloggingPreventionDto.getPage(),waterloggingPreventionDto.getLimit());
list = waterloggingPreventionMapper.getListForPage(waterloggingPreventionDto);
PageInfo<WaterloggingPrevention> pageInfo = new PageInfo<>(list);
waterloggingPreventionDto.setCount(pageInfo.getTotal());
}else {
list = waterloggingPreventionMapper.getListForPage(waterloggingPreventionDto);
}
return list;
}
4.serviceye业务方法接口
/**
* @Description:
* @ClassName: WaterloggingPreventionService
* @Author: songwp
* @Date: 2021/10/16 13:35
*/
public interface WaterloggingPreventionService {
List<WaterloggingPrevention> getListForPage(WaterloggingPreventionDto waterloggingPreventionDto);
}
5.Mapper方法接口
/**
* @Description:
* @ClassName: WaterloggingPreventionMapper
* @Author: songwp
* @Date: 2021/10/16 13:30
*/
@Mapper
public interface WaterloggingPreventionMapper {
List<WaterloggingPrevention> getListForPage(WaterloggingPreventionDto waterloggingPreventionDto);
}
6.参数实体类
/**
* @author songwp
* @Description:
* @date 2021/10/29:47
*/
@Data
public class WaterloggingPreventionDto {
@ApiModelProperty(value = "名称")
private String name;
//分页
@ApiModelProperty(value = "当前页码")
private Integer page; //当前页第一页是0
@ApiModelProperty(value = "每页条数")
private Integer limit;//每页步长
@ApiModelProperty(value = "总条数")
private Long count;//总条数
}