Trigger complains about null pointer but I can't find out why

Question

When we use dataloader to upload records into database we have got the null pointer error when we use the related salesforce Id. But it works when we switch to use external Id.

I am just puzzled to find out the reason.

Below is my related trigger code:

    List<String> relatedOlIdList = new List<String>();
    for(UK_Job__c job : (List<UK_Job__c>)Trigger.New) 
    {
        relatedOlIdList.add(job.UK_Order_Line__c);
    }
    relatedOlMap = new Map<Id, UK_Order_Line__c>([Select    Id, Name, 
                                                            Turnaround__c,
                                                            Transcript_Due__c
                                                    From    UK_Order_Line__c
                                                    Where   Id in :relatedOlIdList]);
//...
        UK_Order_Line__c relatedOl = relatedOlMap.get(job.UK_Order_Line__c);
        if(relatedOl.Transcript_Due__c == null) // This is the line getting null pointer reference error

I have double checked that in the .csv file, the related UK_Order_Line__c Id is valid and does exist in the system. And if we switch into external Id it just works.

But it is really weird that it can't find the relatedOl in this case.

Both code are executed both in before insert and before update.

Answer 1

From the code that you have provided I see that on row

UK_Order_Line__c relatedOl = relatedOlMap.get(job.UK_Order_Line__c);

the variable job is not defined, since you are outside of loop for. That might be the issue for you, unless you haven't provided the complete code..

Answer 2

it will give null pointer if you do not have key in this map relatedOlMap.

use this to avoid errors.

if(relatedOlMap.containsKey(job.UK_Order_Line__c)){
    UK_Order_Line__c relatedOl = relatedOlMap.get(job.UK_Order_Line__c);
}

Hope this helps :)