技术篇-分页查询

1. boot的分页查询

使用PageHelper的starter

1. 在pom.xml中引入依赖

   <dependency>
       <groupId>com.github.pagehelper</groupId>
       <artifactId>pagehelper-spring-boot-starter</artifactId>
       <version>1.2.10</version>
   </dependency>
   
   <dependency>
           <groupId>com.github.pagehelper</groupId>
           <artifactId>pagehelper</artifactId>
           <version>4.1.3</version>
   </dependency>
   

2. 在application.properties或者application.yml格式配置pagehelper的属性

   #pagehelper分页插件配置
   pagehelper.helper-dialect=mysql
   pagehelper.reasonable=true
   pagehelper.support-methods-arguments=true
   pagehelper.params=count=countSql
   

   #分页配置
   pagehelper:
     helper-dialect: mysql
     reasonable: true
     support-methods-arguments: true
     params: count=countSql
   

3. 使用 ：最后就是使用pagehelper进行分页了，其中最重要的一句就是PageHelper.startPage(pageNum,pageSize);pageNum：当前页数 pageSize：当前页需要显示的数量

   @GetMapping("/selectPage")
   @ApiOperation("页查询")
   public ResultPage<String> selectPage(@RequestParam(value = "pageNum", defaultValue = "1") Integer pageNum,
                                        @RequestParam(value = "pageSize", defaultValue = "10") Integer pageSize) {
       PageInfo pageInfo = businessService.selectPage(pageNum, pageSize);
       return new ResultPage<Docker>(ResultCodeEnum.SUCCESS.getCode(), "信息查询成功",
                   pageInfo.getPageNum(),pageInfo.getPages(), pageInfo.getTotal(),pageInfo.getPageSize(), pageInfo.getList());    }
   

   用page.getPages()和getTotal()获取页数和记录总数

    @Override
   public PageInfo selectPage(Integer pageNum, Integer pageSize) {
       PageHelper.startPage(pageNum, pageSize);
       List<String> StringList = businessInformationDao.selectAllStoreNumber();
       PageInfo<String> pageInfo = new PageInfo<>(StringList);
       return pageInfo;
   }
   

2.mongodb的分页查询

前端传递参数的时候会传递页的参数：

page: {pageSize: 15, currentPage: 1, totalRecord: 0}
	currentPage: 1
	pageSize: 15
	totalRecord: 0

后端代码：主要通过参数，调用skip方法和limit方法实现分页查询

//分页
  if (page != null) {
      query2.skip(page.getPageNum());
      query2.limit(page.getPageSize());
  }
//查询实例
  List<Map> maps = mongoTemplate.find(query2, Map.class, "dynamic_collection");

3. 页类

public class Page {

    private Integer currentPage;

    private Integer pageSize;

    private Long totalRecord;

    public Page(Integer currentPage, Integer pageSize, Long totalRecord) {
        this.currentPage = currentPage;
        this.pageSize = pageSize;
        this.totalRecord = totalRecord;
    }

    public Page() {
    }

    public Integer getPageNum() {
        return (currentPage - 1) * pageSize;
    }
}