Hibernate entityManager null pointer exception when confirmed not null

Question

public Guest getGuestByEmailAddress(String emailAddress) {
    try {
        String query 
            = "FROM Guest WHERE Guest.emailAddress = :emailAddress";
        if(entityManager == null) {
            System.out.println("null entityManager");
        } else {
            System.out.println("entity manager not null");
            System.out.println(query);
        }
        Query q = entityManager.createQuery(query);
        q.setParameter("emailAddress", emailAddress);
        return (Guest) q.getSingleResult();
    } catch (EntityNotFoundException e) {
        return null;
    }
}

When run, it prints entity manager not null. An earlier call to another method in the same class using the same entity manager is successful as well.

I have the stack trace:

Nov 04, 2017 3:50:44 PM org.hibernate.hql.internal.QueryTranslatorFactoryInitiator initiateService
INFO: HHH000397: Using ASTQueryTranslatorFactory
Exception in Application start method
java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:389)
    at com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:328)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at sun.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:767)
Caused by: java.lang.RuntimeException: Exception in Application start method
    at com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:917)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication$155(LauncherImpl.java:182)
    at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.NullPointerException
    at java.lang.String$CaseInsensitiveComparator.compare(String.java:1192)
    at java.lang.String$CaseInsensitiveComparator.compare(String.java:1186)
    at java.util.TreeMap.getEntryUsingComparator(TreeMap.java:376)
    at java.util.TreeMap.getEntry(TreeMap.java:345)
    at java.util.TreeMap.get(TreeMap.java:278)
    at org.hibernate.dialect.function.SQLFunctionRegistry.findSQLFunction(SQLFunctionRegistry.java:45)
    at org.hibernate.hql.internal.ast.util.SessionFactoryHelper.findSQLFunction(SessionFactoryHelper.java:369)
    at org.hibernate.hql.internal.ast.tree.IdentNode.getDataType(IdentNode.java:374)
    at org.hibernate.hql.internal.ast.HqlSqlWalker.lookupProperty(HqlSqlWalker.java:654)
    at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.addrExpr(HqlSqlBaseWalker.java:5003)
    at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.expr(HqlSqlBaseWalker.java:1286)
    at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.exprOrSubquery(HqlSqlBaseWalker.java:4707)
    at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.comparisonExpr(HqlSqlBaseWalker.java:4175)
    at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.logicalExpr(HqlSqlBaseWalker.java:2138)
    at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.whereClause(HqlSqlBaseWalker.java:815)
    at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.query(HqlSqlBaseWalker.java:609)
    at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.selectStatement(HqlSqlBaseWalker.java:313)
    at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.statement(HqlSqlBaseWalker.java:261)
    at org.hibernate.hql.internal.ast.QueryTranslatorImpl.analyze(QueryTranslatorImpl.java:266)
    at org.hibernate.hql.internal.ast.QueryTranslatorImpl.doCompile(QueryTranslatorImpl.java:189)
    at org.hibernate.hql.internal.ast.QueryTranslatorImpl.compile(QueryTranslatorImpl.java:141)
    at org.hibernate.engine.query.spi.HQLQueryPlan.<init>(HQLQueryPlan.java:115)
    at org.hibernate.engine.query.spi.HQLQueryPlan.<init>(HQLQueryPlan.java:77)
    at org.hibernate.engine.query.spi.QueryPlanCache.getHQLQueryPlan(QueryPlanCache.java:153)
    at org.hibernate.internal.AbstractSharedSessionContract.getQueryPlan(AbstractSharedSessionContract.java:553)
    at org.hibernate.internal.AbstractSharedSessionContract.createQuery(AbstractSharedSessionContract.java:662)
    at org.hibernate.internal.AbstractSessionImpl.createQuery(AbstractSessionImpl.java:23)
    at com.gitrekt.resort.model.services.GuestService.getGuestByEmailAddress(GuestService.java:49)
    at com.gitrekt.resort.GitRekt.testHibernate(GitRekt.java:95)
    at com.gitrekt.resort.GitRekt.start(GitRekt.java:46)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$162(LauncherImpl.java:863)
    at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$175(PlatformImpl.java:326)
    at com.sun.javafx.application.PlatformImpl.lambda$null$173(PlatformImpl.java:295)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.application.PlatformImpl.lambda$runLater$174(PlatformImpl.java:294)
    at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$148(WinApplication.java:191)
    ... 1 more
Exception running application com.gitrekt.resort.GitRekt

I should note that this is a Java SE environment. No dependency injection, EJB, Spring, or any of that fanciness. Why am I getting a null pointer exception when the entity manager is not null?

This is how I am managing the entityManager in the class where the method in question is called:

private final EntityManager entityManager;

    public GuestService() {
        this.entityManager = HibernateUtil.getEntityManager();
    }

    @Override
    public void finalize() throws Throwable {
        super.finalize();
        this.entityManager.close();
    }

I have called this method immediately before calling the method which throws the exception, and it runs properly:

public Guest getGuestById(Long id) {
        try {
            Guest guest = entityManager.getReference(Guest.class,id);
            return  guest;
        } catch (EntityNotFoundException e) {
            System.out.println("entity not found");
            return null;
        }
    }

What gives?

Entity manager is not null as seen from the stacktrace itself. WHy do you think EM is null? — Akashdeep Saluja
– Akashdeep Saluja, Commented Nov 4, 2017 at 20:18
Then what IS null? I'm clearly getting a null pointer exception. I tried running it through the debugger, and couldn't figure out why it is throwing the NPE — Bassinator
– Bassinator, Commented Nov 4, 2017 at 20:20
query is not null, and entityManager is not null, so what on earth is null? — Bassinator
– Bassinator, Commented Nov 4, 2017 at 20:20
If you see the stack trace closely, something else is null. To do that can you please include the line no. as well for your method in question. — Akashdeep Saluja
– Akashdeep Saluja, Commented Nov 4, 2017 at 20:22

Emir Uner · Accepted Answer · 2017-11-04 20:40:07Z

4

The null pointer exception originates from framework code, not your code.

It seems your specific query causes the problem. Try changing it as follows:

SELECT g FROM Guest g WHERE g.emailAddress = :emailAddress

answered Nov 4, 2017 at 20:40

Emir Uner

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