Error querying database. cannot invoke "Object.hashCode()" because "key" is null

Question

I'm getting the following error

Error Querying database. cannot invoke "Object.hashCode()" because "key" is null

1. stack trace:

org.mybatis.spring.MyBatisSyste Exception: nested
    exception is org.apache.ibatis.exceptions.Pers istenceException:
    ### Error querying database. Cause: java.lang. NullPointerException: Cannot invoke "Object.hashCode()" because "key" is null
    ### The error may exist in class path resource [SbmtMapper.xml]
    ### The error may involve com.delta.crew.dao.mapper.Subm itMapperlfc.getRotnAndLegs
    ### The error occurred while handling results
    ### SQL: WITH ROTATIONS AS (SELECT OP.EMPL ID AS usrld. 'SBMT' AS opType, OVER NB AS version

UNION ALL SELECT RTN.*
FROM ROTATIONS RTN
### Cause: java.lang.NullPointerException: Cannot invoke "Obiect.hashCode(" because "key" is null
at com.delta.crew .dao .SubmitDaolmp-getRotnAndLegs(SubmitDaolmp.java:52) ~[main/:?]
at com delta.crew da SubmitDaolmp$$FastClassBySpringCGLIB$Sd3034a58,.invoke(<generated>)~[main/:?]
at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:218)~[spring-core-5.3.10.jar:5.3.101
at
org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:779)
~[spring-aop-5.3.10.jar:5.3.101
at org.springframework.aop.framework.ReflectiveMethodinvocation.proceed(ReflectiveMethodinvocation.java:163)~
[spring-aop-5.3.10.jar:5.3.101
at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:750)~

The error may exist in some mybatis mapper.xml and the error occurred while handling the results of the below SQL query. The SQL query has null values set.

Example :

Mapper

<resultMap id = "rotsMap" type = SubmitPojo">
<result column="ROTATION_ID" property = "rots_id" />
<result column="ARRIVAL_TIME" property = "arrTime" />
<result column="SBMT_ID" property ="sbmt_id>

Select statement

<select id="getRots" resultMap="rotsMap">
SELECT NULL AS ROTATION_ID
NULL AS ARRIVAL_TIME
OP.SBMT_ID AS SBMT_ID
FROM ROTATION OP;
</select>

I tried setting all the mappings correctly. I'm not sure what went wrong