联表实现回显功能

1.找到这个页面是哪条selection实现的

比如主页面，肯定是不带where条件的整体的sql语句实现的

我这里实现借阅记录中user的nickName的回显

我们在前端date里已经实现了接收了借阅记录的信息存储到recordList:[ ]里

现在只需要进行联表查询即可获得user的nickName属性

2.在BookRecord类里添加User对象

public class BookRecord extends BaseEntity{...private SysUser user;public SysUser getUser() {return user;}public void setUser(SysUser user) {this.user = user;}...
}

3.在bookmapper.xml实现联表查询

<mapper namespace="com.ruoyi.system.mapper.BorrowRecordMapper"><resultMap type="BorrowRecord" id="BorrowRecordResult"><result property="borrowId"    column="borrow_id"    /><result property="borrowNumber"    column="borrow_number"    /><result property="borrowUser"    column="borrow_user"    /><result property="borrrowDate"    column="borrrow_date"    /><result property="planBackDate"    column="plan_back_date"    /><association property="user" javaType="com.ruoyi.common.core.domain.entity.SysUser"><result property="nickName" column="nick_name"/></association></resultMap><resultMap id="BorrowRecordBorrowRecordInfoResult" type="BorrowRecord" extends="BorrowRecordResult"><collection property="borrowRecordInfoList" ofType="BorrowRecordInfo" column="borrow_id" select="selectBorrowRecordInfoList" /></resultMap><resultMap type="BorrowRecordInfo" id="BorrowRecordInfoResult"><result property="biId"    column="bi_id"    /><result property="biBid"    column="bi_bid"    /><result property="biBcount"    column="bi_bcount"    /><result property="brId"    column="br_id"    /><result property="biStatus"    column="bi_status"    /><association property="book" javaType="com.ruoyi.system.domain.Book"><result property="id" column="id"/><result property="name" column="name"/></association></resultMap><sql id="selectBorrowRecordVo">select a.borrow_id, a.borrow_number, a.borrow_user, a.borrrow_date, a.plan_back_date,b.nick_name from t_borrow_record  a left join sys_user b on a.borrow_user = b.user_id</sql><select id="selectBorrowRecordList" parameterType="BorrowRecord" resultMap="BorrowRecordResult"><include refid="selectBorrowRecordVo"/><where>  <if test="borrowNumber != null  and borrowNumber != ''"> and borrow_number = #{borrowNumber}</if><if test="borrowUser != null "> and borrow_user = #{borrowUser}</if><if test="borrrowDate != null "> and borrrow_date = #{borrrowDate}</if><if test="planBackDate != null "> and plan_back_date = #{planBackDate}</if><if test="user != null and user.nickName != null and user.nickName !=''"> and nick_name = #{user.nickName}</if></where></select>

注意写这句的时候一定要加user != null,否则如果你不写非空字段的话，会报user为空的错，其实里面有值，但是加上的话就能骗过编译器

<if test="user != null and user.nickName != null 
and user.nickName !=''"> and nick_name = #{user.nickName}</if>

4.重启后端查看网络

可以看到表单已经有张三了

 5.前端页面回显

只需在prop属性放入user.nickName即可

<el-table-column label="借阅人" align="center" prop="user.nickName" />

。。如果是修改页面回显的话，在修改函数里操作即可

最后实现回显