背景
項(xiàng)目中集成了mybatis plus, 今天在做后臺(tái)的一個(gè)常規(guī)的增刪改查時(shí)，發(fā)現(xiàn)字段值為null時(shí)，這個(gè)字段不會(huì)被保存到數(shù)據(jù)庫
解決辦法
在字段上加上
|
1
|
@TableField(strategy = FieldStrategy.IGNORED) |
strategy字段更新插入策略屬性說明：
IGNORED(0): “忽略判斷”, 所有字段都更新和插入
NOT_NULL(1): “非 NULL 判斷”, 只更新和插入非NULL值
NOT_EMPTY(2): “非空判斷”, 只更新和插入非NULL值且非空字符串
另外一種方式可全局配置，未親手實(shí)踐。
補(bǔ)充：Mybatis查詢數(shù)據(jù)部分字段顯示為null，怎么轉(zhuǎn)成空串("")
1、先定義一個(gè)handler，來把字段為null的轉(zhuǎn)成空串（""）
2、在Mapper.xml中，把可能為空的字段，加上typeHandler屬性，指定處理的handler類的全路徑。
CustomStringTypeHandler.java
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
|
package com.wang.common.mybatis.handler;import org.apache.ibatis.executor.result.ResultMapException;import org.apache.ibatis.type.BaseTypeHandler;import org.apache.ibatis.type.JdbcType;import org.apache.ibatis.type.MappedJdbcTypes;import org.apache.ibatis.type.MappedTypes;import java.sql.CallableStatement;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.SQLException;/** * @Name: CustomStringTypeHandler * @Desc: 自定義mybatis處理類，將null返回為空串（‘'） * @Author: Administrator * @Date: 2019-09-03 18:20 */@MappedTypes({String.class})@MappedJdbcTypes(JdbcType.VARCHAR)public class CustomStringTypeHandler extends BaseTypeHandler<String> { @Override public String getResult(ResultSet rs, String columnName) { String result; try { result = getNullableResult(rs, columnName); } catch (Exception e) { throw new ResultMapException("Error attempting to get column '" + columnName + "' from result set. Cause: " + e, e); } return result; } @Override public void setNonNullParameter(PreparedStatement ps, int i, String parameter, JdbcType jdbcType) throws SQLException { ps.setString(i, parameter); } @Override public String getNullableResult(ResultSet rs, String columnName) throws SQLException { return rs.getString(columnName) == null? "" : rs.getString(columnName); } @Override public String getNullableResult(ResultSet rs, int columnIndex) throws SQLException { return rs.getString(columnIndex) == null? "" : rs.getString(columnIndex); } @Override public String getNullableResult(CallableStatement cs, int columnIndex) throws SQLException { return cs.getString(columnIndex) == null? "" : cs.getString(columnIndex); }} |
Mapper.xml
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
|
<?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.wang.sss.fw.mapper.BusinessTripMapper"> <resultMap id="BaseResultMap" type="com.wang.sss.fw.pojo.BusinessTrip"> <result column="REQUEST_ID" jdbcType="VARCHAR" property="requestId" /> <result column="JOB_NUMBER" jdbcType="VARCHAR" property="jobNumber" /> <result column="REQUEST_DATE" jdbcType="VARCHAR" property="requestDate" /> <result column="DEPARTMENT" jdbcType="VARCHAR" property="department" /> <result column="BUSINESS_DAYS" jdbcType="VARCHAR" property="businessDays"/> <result column="CFD" jdbcType="VARCHAR" property="cfd" /> <result column="MDD" jdbcType="VARCHAR" property="mdd" /> <result column="START_TIME" jdbcType="VARCHAR" property="startTime" /> <result column="END_TIME" jdbcType="VARCHAR" property="endTime" /> <result column="REASON" jdbcType="VARCHAR" property="reason" typeHandler="com.wang.common.mybatis.handler.CustomStringTypeHandler"/> <result column="REMARK" jdbcType="VARCHAR" property="remark" typeHandler="com.wang.common.mybatis.handler.CustomStringTypeHandler"/> </resultMap></mapper> |
沒有加typeHandler屬性，處理之前的查詢結(jié)果：
|
1
|
BusinessTrip(requestId=11925, jobNumber=5721, requestDate=2019-05-06, department=57, businessDays=21, cfd=上海, mdd=南京, startTime=2019-05-06 13:36, endTime=2019-05-07 13:36, reason=null, remark=null) |
增加typeHandler屬性，處理后的結(jié)果：（reason和remark字段都變成了空串）
|
1
|
BusinessTrip(requestId=11925, jobNumber=5721, requestDate=2019-05-06, department=57, businessDays=21, cfd=上海, mdd=南京, startTime=2019-05-06 13:36, endTime=2019-05-07 13:36, reason=, remark=) |
以上為個(gè)人經(jīng)驗(yàn)，希望能給大家一個(gè)參考，也希望大家多多支持服務(wù)器之家。如有錯(cuò)誤或未考慮完全的地方，望不吝賜教。
原文鏈接：https://blog.csdn.net/toalaska/article/details/90085250
