解决mybatis plus字段为null或空字符串无法保存到数据库的问题

@TableField (strategy = FieldStrategy.IGNORED)

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: 自定义mybatis处理类，将null返回为空串（‘'）

  * @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);

   }

}

<? 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 >

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 )

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=)