019 品牌的查询

先看看我们要实现的效果：

点击“品牌管理”菜单：

路由路径：/item/brand

根据路由文件知，对应的页面是：src/pages/item/Brand.vue

页面会发送如下请求：

 注意：程序的编写逻辑

01 Dao层--------数据库对应的实体类及mapper映射

02 Service层-------编写具体的查询方法

03 Controller层------接收url发送的参数和调用service方法

 

1.逻辑思路分析

2.后台提供查询接口

(1)分页结果类PageResult

分页结果类PageResult以后可能在其它项目中也有需求，因此我们将其抽取到leyou-common中，提高复用性。

package lucky.leyou.common.domain;

import java.util.List;

public class PageResult<T> {
    private Long total;// 总条数
    private Integer totalPage;// 总页数
    private List<T> items;// 当前页数据

    public Long getTotal() {
        return total;
    }

    public void setTotal(Long total) {
        this.total = total;
    }

    public Integer getTotalPage() {
        return totalPage;
    }

    public void setTotalPage(Integer totalPage) {
        this.totalPage = totalPage;
    }

    public List<T> getItems() {
        return items;
    }

    public void setItems(List<T> items) {
        this.items = items;
    }
}

不要忘记在leyou-item-service工程的pom.xml中引入leyou-common的依赖：

<dependency>
            <groupId>lucky.leyou.common</groupId>
            <artifactId>leyou-common</artifactId>
            <version>1.0-SNAPSHOT</version>
</dependency>

(2)实体类

package lucky.leyou.item.domain;

import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

@Table(name = "tb_brand")
public class Brand {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;// 品牌名称
    private String image;// 品牌图片
    private Character letter;

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getImage() {
        return image;
    }

    public void setImage(String image) {
        this.image = image;
    }

    public Character getLetter() {
        return letter;
    }

    public void setLetter(Character letter) {
        this.letter = letter;
    }
}

(3)mapper

 通用mapper来简化开发：

package lucky.leyou.item.mapper;

import lucky.leyou.item.domain.Category;
import tk.mybatis.mapper.common.Mapper;

public interface BrandMapper extends Mapper<Category> {
}

(4)service及其实现类

接口

package lucky.leyou.item.service;

import lucky.leyou.common.domain.PageResult;
import lucky.leyou.item.domain.Brand;

public interface IBrandService {
    /**
     * 根据查询条件分页并排序查询品牌信息
     * @param key
     * @param page
     * @param rows
     * @param sortBy
     * @param desc
     * @return
     */
    public PageResult<Brand> queryBrandsByPage(String key, Integer page, Integer rows, String sortBy, Boolean desc);
}

实现类

package lucky.leyou.item.service.impl;

import com.github.pagehelper.PageHelper;
import com.github.pagehelper.PageInfo;
import lucky.leyou.common.domain.PageResult;
import lucky.leyou.item.domain.Brand;
import lucky.leyou.item.mapper.BrandMapper;
import lucky.leyou.item.service.IBrandService;
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 BrandServiceImpl implements IBrandService {

    @Autowired
    private BrandMapper brandMapper;

    /**
     * 根据查询条件分页并排序查询品牌信息
     * @param key
     * @param page
     * @param rows
     * @param sortBy
     * @param desc
     * @return
     */
    @Override
    public PageResult<Brand> queryBrandsByPage(String key, Integer page, Integer rows, String sortBy, Boolean desc) {
        //初始化example 对象
        Example example=new Example(Brand.class);
        Example.Criteria criteria=example.createCriteria();

        //根据数据库表字段name或根据数据库表字段letter进行首字母查询
        if(StringUtils.isNotBlank(key)){
            criteria.andLike("name","%"+key+"%").orEqualTo("letter",key);

        }

        //添加分页条件
        PageHelper.startPage(page,rows);

        //添加排序条件
        if(StringUtils.isNotBlank(sortBy)){
            example.setOrderByClause(sortBy+" "+(desc ? "desc" : "asc"));
        }

        List<Brand> brands = this.brandMapper.selectByExample(example);

        //包装成pageInfo,注意：pageInfo为github上开源的分页工具包的工具类
        PageInfo<Brand> pageInfo=new PageInfo<>(brands);

        //包装成分页结果集返回
        return new PageResult<>(pageInfo.getTotal(),pageInfo.getList());
    }
}

(5)controller

package lucky.leyou.item.controller;

import lucky.leyou.common.domain.PageResult;
import lucky.leyou.item.domain.Brand;
import lucky.leyou.item.service.impl.BrandServiceImpl;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Controller;
import org.springframework.util.CollectionUtils;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;

@Controller
@RequestMapping(path = "/brand")
public class BrandController {
    @Autowired
    private BrandServiceImpl brandService;

    /**
     * 根据查询条件分页并排序查询品牌信息
     * @param key
     * @param page
     * @param rows
     * @param sortBy
     * @param desc
     * @return
     */
    @RequestMapping(path = "/page")
    public ResponseEntity<PageResult<Brand>> queryBrandsByPage(
            @RequestParam(value = "key",required = false) String key,
            @RequestParam(value = "page",defaultValue = "1") Integer page,
            @RequestParam(value = "rows",defaultValue = "5") Integer rows,
            @RequestParam(value = "sortBy",required = false) String sortBy,
            @RequestParam(value = "desc",required = false) Boolean desc
    ){
        //01 调用service中的方法进行品牌查询，返回查询结果集
        PageResult<Brand> brandPageResult = this.brandService.queryBrandsByPage(key, page, rows, sortBy, desc);
        //02 判断返回结果集是否为null 或者返回的结果集的子集为空
        if(CollectionUtils.isEmpty(brandPageResult.getItems())){
            //404
            return ResponseEntity.notFound().build();
        }

        //查询成功
        return ResponseEntity.ok(brandPageResult);
    }


}

2.效果图