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4.Mybatis中，在Mapper的SQL映射文件中，使用＜choose＞＜when＞无法识别参数的情况

news 2025/7/10 5:27:05

正确结果

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.itheima.mapper.BrandMapper"><!-- 完成数据库表和Java代码的映射   --><resultMap id="BrandResultMap" type="brand"><result column="brand_name" property="brandName"></result><result column="company_name" property="companyName"></result></resultMap><select id="selectByConditionSingle" resultMap="BrandResultMap">select *from tb_brandwhere<choose><!--相当于switch--><when test="status != null"><!--相当于case-->status = #{status}</when><when test="companyName != null and companyName != '' "><!--相当于case-->company_name like #{companyName}</when><when test="brandName != null and brandName != ''"><!--相当于case-->brand_name like #{brandName}</when><otherwise>1 = 1</otherwise></choose></select>
</mapper>

在这里插入图片描述
由于使用Brand对象传参，此时使用标签，没有给Brand对象赋值，此时应该查询数据库的三条记录

但是，如果因为实体类的变量数据类型为基本类型，而不是它的包装类型，可能会出现如下错误

在这里插入图片描述
此时，status的默认值就会变为0，达不到预期的效果
下方为正确的实体类代码

package com.itheima.pojo;/*** @package: com.itheima.pojo* @className: Brand* @Description:* @author: haozihua* @date: 2024/11/8 10:32*/
public class Brand {private Integer id;private String brandName;private String companyName;private Integer ordered;private String description;private Integer status;public Integer getId() {return id;}public void setId(Integer id) {this.id = id;}public String getBrandName() {return brandName;}public void setBrandName(String brandName) {this.brandName = brandName;}public String getCompanyName() {return companyName;}public void setCompanyName(String companyName) {this.companyName = companyName;}public Integer getOrdered() {return ordered;}public void setOrdered(Integer ordered) {this.ordered = ordered;}public String getDescription() {return description;}public void setDescription(String description) {this.description = description;}public Integer getStatus() {return status;}public void setStatus(Integer status) {this.status = status;}@Overridepublic String toString() {return "Brand{" +"id=" + id +", brandName='" + brandName + '\'' +", companyName='" + companyName + '\'' +", ordered=" + ordered +", description='" + description + '\'' +", status=" + status +'}';}
}