java.lang.NullPointerException in CreateNamedQuery

Question

I have the following code which is resulting in a java.lang.NullPointerException:

List results = em.createNamedQuery("User.findByUserName").setParameter("userName", username).getResultList();

User is the entity bean, which contains:

@NamedQuery(name = "User.findByUserName", query = "SELECT u FROM User u WHERE u.userName = :userName"),

Does anyone know why?

I am not getting the stack trace of the exception . The webpage stays in the same page. — Shilpa, Oct 15 '12 at 07:20
You should be getting the stacktrace *somewhere*, for example in the server logs. Unless you've manually caught the exception and not used `e.printStackTrace()`. In that case you should fix that. — Joachim Sauer, Oct 15 '12 at 07:21
I meant the stack trace that we see on the localhost. In the server log, it says INFO: Caught exception in UserFacade java.lang.NullPointerException. — Shilpa, Oct 15 '12 at 07:23
Probably EntityManager (em) is null. Check that. Your query is right. — vels4j, Oct 15 '12 at 07:25

Miljen Mikic · Answer 1 · 2012-10-15T07:47:06.817

1

A method getResultList() doesn't throw NullPointerException (it returns empty list if there's no match), so I'm guessing that it should be one of the following:

you didn't inject/initialize EntityManager em (did you forget @PersistenceContext annotation?)
String username is null

In case of EntityManager null, check whether you have persistence.xml file (it's mandatory!). It should look like:

<persistence version="2.0" xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd">
  <persistence-unit name="OEMSPU" transaction-type="JTA">
    <provider>oracle.toplink.essentials.PersistenceProvider</provider>
    <jta-data-source>ADD JNDI NAME OF YOUR DATASOURCE, e.g. jdbc/sample</jta-data-source>
    <exclude-unlisted-classes>false</exclude-unlisted-classes>
    <properties/>
  </persistence-unit>
</persistence>

edited Oct 15 '12 at 07:47

answered Oct 15 '12 at 07:28

Miljen Mikic

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I do have the @PersistenceContext(unitName = "OEMSPU"). String username is not null either as I have printed it out to check. – Shilpa Oct 15 '12 at 07:30
1

Please check in your code whether `em` is null or not prior to calling named query. – Miljen Mikic Oct 15 '12 at 07:36
Yes, I do have the persistence.xml file. OEMS false – Shilpa Oct 15 '12 at 07:46
You're missing tag, and alternatively, throw out the `(unitName = "OEMSPU")` part, i.e. just use `@PersistenceContext` annotation without any parameters. – Miljen Mikic Oct 15 '12 at 07:49
MAde the changes u told, still the same – Shilpa Oct 15 '12 at 07:53
Does injection works in case of your class, i.e. are you using this annotation in container-handled class (EJB, servlet..) or in POJO? – Miljen Mikic Oct 15 '12 at 08:01
I am using the annotation in EJB : session beans – Shilpa Oct 15 '12 at 16:02
Huh..the last thing that comes to my mind is that JDBC resource `OEMS` doesn't exist or it's not deployed on your cluster/standalone instance. – Miljen Mikic Oct 15 '12 at 20:04
Which application server are you using? – Miljen Mikic Oct 21 '12 at 09:03
I had not injected the EJB in managed bean, thats why I was getting the error. Thanks for your help :) – Shilpa Oct 24 '12 at 04:45

score 0 · Answer 2 · answered Jun 20 '13 at 09:10

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Try making it a Stateless Bean by adding @Stateless annotation above the public class. Worked for me.

answered Jun 20 '13 at 09:10

Tsonev

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score 0 · Answer 3 · answered Dec 09 '15 at 21:31

This can come about when your psql is referencing an entity property name. I was doing something like :param.user = x.user in my psql, but trying to grab the property "user" from a param (which hasn't been passed in yet when createQuery runs) was giving me the NPE. I wish this sort of thing were possible, though..

java.lang.NullPointerException in CreateNamedQuery

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