Getting null pointer exception when jpa query not found a row in database

Question

I'm trying to get result of my query from my database with jpa. When the query founds nothing in the database, it returns null pointer exception. I tried to check it if statement like in below code but I still getting null pointer exception.

public List<String> getQuestionSavedUser(String salesOrder, String module,int questionID)
    {
        List<String> singleUser= entityManager.createQuery("select i.savedBy from EVMResponses i where i.salesOrder='"+salesOrder+"' AND i.module='"+module+"' AND i.questionID="+questionID+"", String.class).getResultList(); 
        System.out.println(singleUser.size());
        if(singleUser.size()>0&&singleUser.get(0)!=null)
        {
            users.add(singleUser.get(0));
        }
        else
        {
            users.add("");
        }
        return users;
    }

How can I solve this problem?

Please read Under what circumstances may I add “urgent” or other similar phrases to my question, in order to obtain faster answers? - the summary is that this is not an ideal way to address volunteers, and is probably counterproductive to obtaining answers. Please refrain from adding this to your questions. — halfer
– halfer, Commented May 21, 2021 at 20:52

fino · Accepted Answer · 2021-05-20 13:52:38Z

1

try this:

public List<String> getQuestionSavedUser(String salesOrder, String module,int questionID)
    {
        List<String> users = new ArrayList<>();
        List<String> singleUser= entityManager.createQuery("select i.savedBy from EVMResponses i where i.salesOrder='"+salesOrder+"' AND i.module='"+module+"' AND i.questionID="+questionID+"", String.class).getResultList(); 
        System.out.println(singleUser.size());
        if(singleUser.size()>0&&singleUser.get(0)!=null)
        {
            users.add(singleUser.get(0));
        }
        else
        {
            users.add("");
        }
        return users;
    }

answered May 20, 2021 at 13:52

fino

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1 Comment

demir5334 Over a year ago

You're right when I forgot to define users, after the defining the problem solved. Thanks.

fino · Accepted Answer · 2021-05-20 13:21:56Z

0

Maybe the entityManager is null,check it!
or you can use:

List<String> singleUser = new ArrayList<>();
singleUser = entityManager.createQuery("select i.savedBy from EVMResponses i where i.salesOrder='"+salesOrder+"' AND i.module='"+module+"' AND i.questionID="+questionID+"", String.class).getResultList();

to see whether entityManager works well or not. \

answered May 20, 2021 at 13:21

fino

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3 Comments

demir5334 Over a year ago

The entityManager works fine and it's not null also I tried with this List<String> singleUser = new ArrayList<>(); but I'm still getting error on this code users.add(singleUser.get(0));

fino Over a year ago

seems that you never define the users

fino Over a year ago

i rewrite an answer, it may suit this

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