简单的分页查询的实现接口

package com.leyou.controller;

import com.leyou.PageResult;
import com.leyou.service.BrandService;
import com.pojo.Brand;
import org.apache.commons.lang.StringUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("brand")
public class BrandController {

    @Autowired
    private BrandService brandService;
    @GetMapping("page")
    public ResponseEntity<PageResult<Brand>> queryBrand(@RequestParam(value ="page",required = false,defaultValue = "1")int page
    ,@RequestParam(value ="rows",defaultValue = "5",required = false)int rows,
     @RequestParam(value = "sortBy",required = false)String sortBy,
     @RequestParam(value = "desc",required = false) boolean desc,
     @RequestParam(value = "key",required = false) String key
    ){

     //使用service来进行分页查询
    PageResult<Brand>  list=  this.brandService.queryBrandByPage(page,rows,sortBy,desc,key);

    //得到查询的结果进行判断再返回
        if(list==null){
            //如果查询结果是空的话，则可以返回404
         return ResponseEntity.notFound().build();
        }

        return ResponseEntity.ok(list);



    }
}

 

 

 

package com.leyou.service;

import com.github.pagehelper.Page;
import com.github.pagehelper.PageHelper;
import com.leyou.PageResult;
import com.leyou.mapper.BrandMapper;
import com.pojo.Brand;
import org.apache.commons.lang.StringUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import tk.mybatis.mapper.entity.Example;

import java.util.List;

@Service
public class BrandService {
    @Autowired
    private BrandMapper brandMapper;


    public PageResult<Brand> queryBrandByPage(int page, int rows, String sortBy, boolean desc, String key) {
        //使用分页助手来实现分页查询
        //开启分页,第一个参数是当前页数，第二个参数是每页的条数
        PageHelper.startPage(page,rows);

        //使用eaample对象进行查询，则创建一个与需要查询类关联的example对象
        Example example = new Example(Brand.class);

        //实现对查询条件的拼接


        if(StringUtils.isNotBlank(key)){
            //如果key存在，则实现在查询的后面添上模糊查询
            example.createCriteria().andLike("name","%"+key+"%").orEqualTo("letter",key);

        }

        if(StringUtils.isNotBlank(sortBy)){
            //如果排序对象存在，则需要在后面添上按照传递过来的sortBy和desc进行排序排序
            //分页查询的条件就是mysql后面查询条件的拼接
           String orderBYclause=sortBy+( desc ? "DESC":"ASC");
           example.setOrderByClause(orderBYclause);

        }





        //执行查询
        //查询出来的结果可以用page<T>来进行封装,可以得到查询的所有结果
        Page<Brand> brands = (Page<Brand>) this.brandMapper.selectByExample(example);

           //返回的结果是pageResult类型
        return new PageResult<>(brands.getTotal(),brands);

    }
}