項目中集成了mybatis plus, 今天在做后臺的一個常規的增刪改查時，發現字段值為null時，這個字段不會被保存到數據庫

在字段上加上

@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，未親手實踐。

補充：Mybatis查詢數據部分字段顯示為null，怎么轉成空串('')

1、先定義一個handler，來把字段為null的轉成空串（''）

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

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

<?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 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，處理之前的查詢結果：

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，處理后的結果：（reason和remark字段都變成了空串）

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=)

以上為個人經驗，希望能給大家一個參考，也希望大家多多支持好吧啦網。如有錯誤或未考慮完全的地方，望不吝賜教。