MybatisPlus实现多表的关联查询,实现分页,多条件查询全过程

SELECT
	t1.*, t2. NAME supplierName
FROM
	tb_goods t1
LEFT JOIN tb_supplier t2 
ON t1.supplier_id = t2.id
WHERE
t1.name like '%S%'
AND t1.code like '%Spring%'
AND t1.supplier_id=1

package com.jhj.member.req;

import lombok.Data;

/**
 * @program: jhjmember
 * @ClassName GoodsREQ
 * @description:
 * @author:蒋皓洁
 * @create: 2020-08-19 15:21
 * @Version 1.0
 * 商品的请求类，接收请求参数
 **/
@Data
public class GoodsREQ {
    /**
     * 商品名称
     */
    private String name;

    /**
     * 商品编码
     */
    private String code;
    /**
     * 供应商id
     */
    private Integer supplierId;
}

 /**
     * goods表中没有这个字段，所以这里要用，TableFiled标识字段，不然要报错
     */
    @TableField(exist = false)
    private  String supplierName;

package com.jhj.member.entity;

import java.math.BigDecimal;

import com.baomidou.mybatisplus.annotation.TableField;
import com.baomidou.mybatisplus.annotation.TableName;
import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableId;
import java.io.Serializable;
import lombok.Data;
import lombok.EqualsAndHashCode;
import lombok.experimental.Accessors;

/**
 * <p>
 * 商品信息表
 * </p>
 *
 * @author 蒋皓洁
 * @since 2020-08-18
 */
@Data
@EqualsAndHashCode(callSuper = false)
@Accessors(chain = true)
@TableName("tb_goods")
public class Goods implements Serializable {

    private static final long serialVersionUID = 1L;

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

    /**
     * 商品名称
     */
    private String name;

    /**
     * 商品编码
     */
    private String code;

    /**
     * 商品规格
     */
    private String spec;

    /**
     * 零售价
     */
    private BigDecimal retailPrice;

    /**
     * 进货价
     */
    private BigDecimal purchasePrice;

    /**
     * 库存数量
     */
    private Integer storageNum;

    /**
     * 供应商id
     */
    private Integer supplierId;


    /**
     * goods表中没有这个字段，所以这里要用，TableFiled标识字段，不然要报错
     */
    @TableField(exist = false)
    private  String supplierName;


}

public interface GoodsMapper extends BaseMapper<Goods> {
    /**
     *
     * @param page
     * @param req
     * @return
     *
     *
     * 分页查询商品的列表
     * 1、第一个参数传递分页的对象page (此对象封装当前页码，还有显示查询多少)
     *
     * 2、第二个参数，查询条件，@Param取别名，
     *  @Param("req")这个取的别名，方便xml里面使用
     */

      IPage<Goods>searchPage(IPage<Goods> page, @Param("req")GoodsREQ req);
}

mybatis-plus:
  # 扫描实体类所在的包，这样在mapper.xml文件中就不用配置实体类全路径，直接写类名就行
  type-aliases-package: com.jhj.member.entity
  #  扫描xml包下面的xml文件
  mapper-locations: classpath:com/jhj/member/mapper/xml/**.xml
  #  配置日志级别

  < if test="req.name !=null and req.name!=''">
            and t1.name like CONCAT('%',#{req.name},'%')
  </ if >

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.jhj.member.mapper.GoodsMapper">

    <select id="searchPage" resultType="Goods">
        SELECT
        t1.*, t2.name supplierName
        FROM
        tb_goods t1
        LEFT JOIN tb_supplier t2 ON t1.supplier_id = t2.id
        WHERE 1=1
        <if test="req.name !=null and req.name!=''">
            and t1.name like CONCAT('%',#{req.name},'%')
        </if>
        <if test="req.code!=null and req.code!=''">
            and  t1.code like CONCAT('%',#{req.code},'%')
        </if>
        <if test="req.supplierId!=null">
            and t1.supplier_id=#{req.supplierId}
        </if>
    </select>
</mapper>

public interface IGoodsService extends IService<Goods> {
    List<Goods>SlectBySupplierId(int id);

    Result search (Long page, Long size, GoodsREQ req);
}

  @Override
    public Result search(Long page, Long size, GoodsREQ req) {
        /**
         *因为mapper.xml已经对查询条件进行筛选和拼接了
         */
        if (req==null){
            req=new GoodsREQ();
        }
        IPage data = baseMapper.searchPage(new Page<Goods>(page, size), req);
        return Result.ok(data);
    }

  @Autowired
    private IGoodsService goodsService;


    /**
     *
     * @param page
     * @param size
     * @param req
     * @return
     *
     */
    @PostMapping("/list/search/{page}/{size}")
    public Result search(
            @PathVariable("page") long page,
            @PathVariable("size") long size,
            @RequestBody (required = false)    GoodsREQ req
            ){

       return goodsService.search(page,size,req);
    }