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:蔣皓潔
 * @create: 2020-08-19 15:21
 * @Version 1.0
 * 商品的請(qǐng)求類，接收請(qǐng)求參數(shù)
 **/
@Data
public class GoodsREQ {
    /**
     * 商品名稱
     */
    private String name;

    /**
     * 商品編碼
     */
    private String code;
    /**
     * 供應(yīng)商id
     */
    private Integer supplierId;
}

 /**
     * goods表中沒(méi)有這個(gè)字段，所以這里要用，TableFiled標(biāo)識(shí)字段，不然要報(bào)錯(cuò)
     */
    @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 蔣皓潔
 * @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;

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

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

    /**
     * 商品編碼
     */
    private String code;

    /**
     * 商品規(guī)格
     */
    private String spec;

    /**
     * 零售價(jià)
     */
    private BigDecimal retailPrice;

    /**
     * 進(jìn)貨價(jià)
     */
    private BigDecimal purchasePrice;

    /**
     * 庫(kù)存數(shù)量
     */
    private Integer storageNum;

    /**
     * 供應(yīng)商id
     */
    private Integer supplierId;


    /**
     * goods表中沒(méi)有這個(gè)字段，所以這里要用，TableFiled標(biāo)識(shí)字段，不然要報(bào)錯(cuò)
     */
    @TableField(exist = false)
    private  String supplierName;


}

public interface GoodsMapper extends BaseMapper<Goods> {
    /**
     *
     * @param page
     * @param req
     * @return
     *
     *
     * 分頁(yè)查詢商品的列表
     * 1、第一個(gè)參數(shù)傳遞分頁(yè)的對(duì)象page (此對(duì)象封裝當(dāng)前頁(yè)碼，還有顯示查詢多少)
     *
     * 2、第二個(gè)參數(shù)，查詢條件，@Param取別名，
     *  @Param("req")這個(gè)取的別名，方便xml里面使用
     */

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

mybatis-plus:
  # 掃描實(shí)體類所在的包，這樣在mapper.xml文件中就不用配置實(shí)體類全路徑，直接寫類名就行
  type-aliases-package: com.jhj.member.entity
  #  掃描xml包下面的xml文件
  mapper-locations: classpath:com/jhj/member/mapper/xml/**.xml
  #  配置日志級(jí)別

  < 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?yàn)閙apper.xml已經(jīng)對(duì)查詢條件進(jìn)行篩選和拼接了
         */
        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);
    }