7.查询热销商品前四名的实现

1.数据库

CREATE TABLE t_product (
  id int(20) NOT NULL COMMENT '商品id',
  category_id int(20) DEFAULT NULL COMMENT '分类id',
  item_type varchar(100) DEFAULT NULL COMMENT '商品系列',
  title varchar(100) DEFAULT NULL COMMENT '商品标题',
  sell_point varchar(150) DEFAULT NULL COMMENT '商品卖点',
  price bigint(20) DEFAULT NULL COMMENT '商品单价',
  num int(10) DEFAULT NULL COMMENT '库存数量',
  image varchar(500) DEFAULT NULL COMMENT '图片路径',
  status int(1) DEFAULT '1' COMMENT '商品状态  1：上架   2：下架   3：删除',
  priority int(10) DEFAULT NULL COMMENT '显示优先级',
  created_time datetime DEFAULT NULL COMMENT '创建时间',
  modified_time datetime DEFAULT NULL COMMENT '最后修改时间',
  created_user varchar(50) DEFAULT NULL COMMENT '创建人',
  modified_user varchar(50) DEFAULT NULL COMMENT '最后修改人',
  PRIMARY KEY (id)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

2.product实体类

package com.ku.store.entity;

import lombok.Data;

@Data
public class Product extends BaseEntity{
    private Integer id;
    private Integer categoryId;//类别id
    private String itemType;//项目
    private String title;
    private String sellPoint;//销售点
    private Long price;
    private Integer num;
    private String image;
    private Integer status;
    private Integer priority;//优先权
}

3.mapper层

　　3.1.接口实现

/**
     * 查询热销商品前四名
     * @return 热销商品前四名的集合
     */
    List<Product> findHostList();

　　3.2.接口的xml实现

<resultMap id="ProductEntityMap" type="com.ku.store.entity.Product">
        <id column="id" property="id"/>
        <result column="category_id" property="categoryId"/>
        <result column="item_type" property="itemType"/>
        <result column="sell_point" property="sellPoint"/>
        <result column="created_user" property="createdUser"/>
        <result column="created_time" property="createdTime"/>
        <result column="modified_user" property="modifiedUser"/>
        <result column="modified_time" property="modifiedTime"/>
    </resultMap>

    <!-- 查询热销商品的前四名：List<Product> findHostList() -->
    <select id="findHostList" resultMap="ProductEntityMap">
        select
            *
        from
            store.t_product
        where
            status = 1
        order by
            priority desc
            limit 0,4
    </select>

　　3.3.测试接口方法

@Autowired
    ProductMapper productMapper;
    @Test
    public void findHostList(){
        List<Product> hostList = productMapper.findHostList();
        System.out.println("count："+hostList.size());
        for (Product product : hostList) {
            System.out.println(product);
        }
    }

　　3.4.测试结果

4.service层

　　4.1.接口实现

List<Product> getHostList();

　　4.2.接口实现类

@Service
public class ProductServiceImpl implements IProductService {

    @Autowired
    private ProductMapper productMapper;

    @Override
    public List<Product> getHostList() {
        List<Product> list = productMapper.findHostList();
        for (Product product : list) {
            product.setCreatedUser(null);
            product.setCreatedTime(null);
            product.setModifiedUser(null);
            product.setModifiedTime(null);
        }
        return list;
    }
}

　　4.3.实现类测试

@Autowired
    IProductService productService;

    @Test
    public void getHostList(){
        try {
            List<Product> list = productService.getHostList();
            System.out.println("count=" + list.size());
            for (Product item : list) {
                System.out.println(item);
            }
        } catch (ServiceException e) {
            System.out.println(e.getClass().getSimpleName());
            System.out.println(e.getMessage());
        }
    }

　　4.4.测试结果

5.controller层

　　5.1.增强BaseController

　　5.2.实现ProductController

@RestController
@RequestMapping("/products")
public class ProductController extends BaseController{
    @Autowired
    private IProductService productService;

    @GetMapping("hot_list")
    public JsonResult<List<Product>> getHotList(){
        List<Product> data = productService.getHostList();
        return new JsonResult<>(OK, data);
    }
}

　　5.3.postman测试