Mybatis-Plus一对多及分页

Mybatis-Plus一对多及分页

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需求中一个商品对应多个类型的多个图片，由于商品信息和商品相关图片是分表根据商品id关联存的，所以这就涉及到了关联查询。对这个不是很了解，所以网上搜了一圈，说的那叫一个花里胡哨啊，好几种方式以及贴的代码，看的人脑阔疼，尝试出了一种比较简单的方式，分享一下。

首先分享一下我的代码，两个实体类，即代表两张表。一个商品类，一个商品图片类。一个商品对应好多张图片，一对多的关系。采用Mapper.xml实现，看网上有完全基于注解实现的，看了一下比较懵，xml比较熟悉。

商品类（重点看最后两个list类型的字段）：

@Data
@EqualsAndHashCode(callSuper = false)
@Accessors(chain = true)
public class Product implements Serializable {

    private static final long serialVersionUID = 1L;

    /**
     * 用户id
     */
    @TableId(value = "id", type = IdType.AUTO)
    private Long id;

    /**
     * 产品类别，1：原材料，2：设备
     */
    @TableField("type")
    private Integer type;

    /**
     * 产品名称
     */
    @TableField("name")
    private String name;

    /**
     * 品牌
     */
    @TableField("brand")
    private String brand;

    /**
     * 产地
     */
    @TableField("place")
    private String place;

    /**
     * 价格
     */
    @TableField("price")
    private Integer price;

    /**
     * 库存量
     */
    @TableField("stock")
    private Integer stock;

    /**
     * 运费
     */
    @TableField("carriage")
    private Integer carriage;

    /**
     * 销量
     */
    @TableField("sales_volume")
    private Integer salesVolume;

    /**
     * 采购次数
     */
    @TableField("purchase_number")
    private Integer purchaseNumber;
    /**
     * 更新时间
     */
    @TableField("update_time")
    private Date updateTime;

    /**
     * 创建时间
     */
    @TableField("create_time")
    private Date createTime;

    /**
     * 商品展示图列表
     */
    private List showImages;

    /**
     * 商品详情图列表
     */
    private List infoImages;
}

商品图片类：

@Data
@EqualsAndHashCode(callSuper = false)
@Accessors(chain = true)
public class Images implements Serializable {

    private static final long serialVersionUID = 1L;

    /**
     * 图片id
     */
    @TableId(value = "id", type = IdType.AUTO)
    private Integer id;

    /**
     * 图片地址
     */
    @TableField("url")
    private String url;

    /**
     * 图片优先级，从小到大优先级依次减小
     */
    @TableField("url")
    private Integer order;

    /**
     * 图片类型，1：展示图，2：详情图
     */
    @TableField("type")
    private Integer type;
    /**
     * 备注
     */
    @TableField("remark")
    private String remark;

    /**
     * 更新时间
     */
    @TableField("update_time")
    private Date updateTime;

    /**
     * 创建时间
     */
    @TableField("create_time")
    private Date createTime;
}

ProductMapper.java

@Mapper
public interface ProductMapper extends BaseMapper {

//    IPage getProduct(IPage page, @Param("id") Integer id);

    IPage getProduct(IPage page);

    List getShowImages(Long productId);

    List getInfoImages(Long productId);

}

ProductMapper.xml

    
    
        
        
        
        
        
        
        
        
        
        
        
        
        
        
    

    
    
        id, type, name, brand, place, price, stock, carriage, sales_volume, purchase_number
    

    
        select * from mall.product
    


    
        select *from mall.images where product_id = #{productId} and type = 1
    

    
        select *from mall.images where product_id = #{productId} and type = 2
    
    

xml说明：

1. xml上面的映射resultMap中使用collection标签来完成一对多。
2. collection标签中property属性的值跟Product实体类中的最后两个List属性对应，查出的多条图片的数据会映射到Product这两个属性中。
3. collection标签中column属性值为prodcut中的id，要根据这个id去images表中查询图片。
4. collection标签中id属性值为查询图片的sql id。

测试代码

void getProduct() {
        // 构建分页对象
        IPage page = new Page(1, 10);
        IPage product = mapper.getProduct(page);
        System.out.println(JSON.toJSONString(product));
    }

注：使用mybatis-plus分页功能记得加入分页拦截器，否则分页不会生效。

测试结果：

{
    "current": 1,
    "pages": 1,
    "records": [
        {
            "id": 1,
            "infoImages": [{
                "createTime": 1583231923000,
                "id": 2,
                "order": 2,
                "remark": "q",
                "type": 2,
                "updateTime": 1583231923000,
                "url": "b"
            }],
            "name": "test",
            "showImages": [{
                "createTime": 1583231918000,
                "id": 1,
                "order": 1,
                "remark": "q",
                "type": 1,
                "updateTime": 1583231918000,
                "url": "a"
            }],
            "updateTime": 1583231907000
        },
        {
            "id": 2,
            "infoImages": [{
                "createTime": 1583235037000,
                "id": 4,
                "order": 2,
                "remark": "b",
                "type": 2,
                "updateTime": 1583235030000,
                "url": "d"
            }],
            "name": "test2",
            "showImages": [{
                "createTime": 1583235033000,
                "id": 3,
                "order": 1,
                "remark": "q",
                "type": 1,
                "updateTime": 1583235028000,
                "url": "d"
            }],
            "updateTime": 1583234967000
        }
    ],
    "searchCount": true,
    "size": 10,
    "total": 2
}

测试日志：

2020-03-03 19:46:41.997 DEBUG [,,,] 14776 --- [           main]     : ==>  Preparing: SELECT COUNT(1) FROM mall.product 
2020-03-03 19:46:42.033 DEBUG [,,,] 14776 --- [           main]     : ==> Parameters: 
2020-03-03 19:46:42.078 DEBUG [,,,] 14776 --- [           main]     : ==>  Preparing: select * from mall.product LIMIT ?,? 
2020-03-03 19:46:42.089 DEBUG [,,,] 14776 --- [           main]     : ==> Parameters: 0(Long), 10(Long)
2020-03-03 19:46:42.110 DEBUG [,,,] 14776 --- [           main]     : ====>  Preparing: select *from mall.images where product_id = ? and type = 1 
2020-03-03 19:46:42.113 DEBUG [,,,] 14776 --- [           main]     : ====> Parameters: 1(Long)
2020-03-03 19:46:42.129 DEBUG [,,,] 14776 --- [           main]     : <====      Total: 1
2020-03-03 19:46:42.130 DEBUG [,,,] 14776 --- [           main]     :  Time：20 ms - ID：com.angsi.lianlian.mapper.ProductMapper.getShowImagesExecute SQL：select *from mall.images where product_id = 1 and type = 1
2020-03-03 19:46:42.133 DEBUG [,,,] 14776 --- [           main]     : ====>  Preparing: select *from mall.images where product_id = ? and type = 2 
2020-03-03 19:46:42.135 DEBUG [,,,] 14776 --- [           main]     : ====> Parameters: 1(Long)
2020-03-03 19:46:42.150 DEBUG [,,,] 14776 --- [           main]     : <====      Total: 1
2020-03-03 19:46:42.151 DEBUG [,,,] 14776 --- [           main]     :  Time：16 ms - ID：com.angsi.lianlian.mapper.ProductMapper.getInfoImagesExecute SQL：select *from mall.images where product_id = 1 and type = 2
2020-03-03 19:46:42.152 DEBUG [,,,] 14776 --- [           main]     : ====>  Preparing: select *from mall.images where product_id = ? and type = 1 
2020-03-03 19:46:42.155 DEBUG [,,,] 14776 --- [           main]     : ====> Parameters: 2(Long)
2020-03-03 19:46:42.169 DEBUG [,,,] 14776 --- [           main]     : <====      Total: 1
2020-03-03 19:46:42.170 DEBUG [,,,] 14776 --- [           main]     :  Time：14 ms - ID：com.angsi.lianlian.mapper.ProductMapper.getShowImagesExecute SQL：select *from mall.images where product_id = 2 and type = 1
2020-03-03 19:46:42.170 DEBUG [,,,] 14776 --- [           main]     : ====>  Preparing: select *from mall.images where product_id = ? and type = 2 
2020-03-03 19:46:42.173 DEBUG [,,,] 14776 --- [           main]     : ====> Parameters: 2(Long)
2020-03-03 19:46:42.187 DEBUG [,,,] 14776 --- [           main]     : <====      Total: 1
2020-03-03 19:46:42.188 DEBUG [,,,] 14776 --- [           main]     :  Time：16 ms - ID：com.angsi.lianlian.mapper.ProductMapper.getInfoImagesExecute SQL：select *from mall.images where product_id = 2 and type = 2
2020-03-03 19:46:42.188 DEBUG [,,,] 14776 --- [           main]     : <==      Total: 2
2020-03-03 19:46:42.188 DEBUG [,,,] 14776 --- [           main]     :  Time：94 ms - ID：com.angsi.lianlian.mapper.ProductMapper.getProductExecute SQL：select * from mall.product LIMIT 0,10
{"current":1,"pages":1,"records":[{"id":1,"infoImages":[{"createTime":1583231923000,"id":2,"order":2,"remark":"q","type":2,"updateTime":1583231923000,"url":"b"}],"name":"test","showImages":[{"createTime":1583231918000,"id":1,"order":1,"remark":"q","type":1,"updateTime":1583231918000,"url":"a"}],"updateTime":1583231907000},{"id":2,"infoImages":[{"createTime":1583235037000,"id":4,"order":2,"remark":"b","type":2,"updateTime":1583235030000,"url":"d"}],"name":"test2","showImages":[{"createTime":1583235033000,"id":3,"order":1,"remark":"q","type":1,"updateTime":1583235028000,"url":"d"}],"updateTime":1583234967000}],"searchCount":true,"size":10,"total":2}

通过日志和数据，可以看出，在查询商品之后，查询了商品图片，实现我想要的一对多分页。