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hibernatejpajpa-2.0inner-joinjpql

Why do I get an invalid path when I try and construct a JPQL join query?

I’m using JPA 2.1, Hibernate 4.3.6.Final, and MySQL 5.5.37. How do I write a JPQL query that does a join? I’m trying below

    final String jpqlQuery = "SELECT m FROM Message m LEFT JOIN MessageReadDate mr " + 
            " INNER JOIN m.group g " + 
            " LEFT JOIN g.classroom c " + 
            " LEFT JOIN c.ROSTER u WHERE " + 
            " u.USER = :recipient AND " + 
            " u.ENABLED = 1 AND " + 
            " c.ENABLED = 1 AND " + 
            " g.NAME = '' AND " +
            " m.author <> :author";
    Query query = m_entityManager.createQuery(jpqlQuery);

but getting the error “Path expected for join! … Invalid path: 'g.classroom'”.

org.hibernate.hql.internal.ast.ErrorCounter -  Path expected for join!
 Path expected for join!
        at org.hibernate.hql.internal.ast.HqlSqlWalker.createFromJoinElement(HqlSqlWalker.java:379)
        at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.joinElement(HqlSqlBaseWalker.java:3903)
        at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.fromElement(HqlSqlBaseWalker.java:3689)
        at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.fromElementList(HqlSqlBaseWalker.java:3567)
        at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.fromClause(HqlSqlBaseWalker.java:708)
        at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.query(HqlSqlBaseWalker.java:564)
        at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.selectStatement(HqlSqlBaseWalker.java:301)
        at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.statement(HqlSqlBaseWalker.java:249)
        at org.hibernate.hql.internal.ast.QueryTranslatorImpl.analyze(QueryTranslatorImpl.java:278)
        at org.hibernate.hql.internal.ast.QueryTranslatorImpl.doCompile(QueryTranslatorImpl.java:206)
        at org.hibernate.hql.internal.ast.QueryTranslatorImpl.compile(QueryTranslatorImpl.java:158)
        at org.hibernate.engine.query.spi.HQLQueryPlan.<init>(HQLQueryPlan.java:126)
        at org.hibernate.engine.query.spi.HQLQueryPlan.<init>(HQLQueryPlan.java:88)
        at org.hibernate.engine.query.spi.QueryPlanCache.getHQLQueryPlan(QueryPlanCache.java:167)
        at org.hibernate.internal.AbstractSessionImpl.getHQLQueryPlan(AbstractSessionImpl.java:301)
        at org.hibernate.internal.AbstractSessionImpl.createQuery(AbstractSessionImpl.java:236)
        at org.hibernate.internal.SessionImpl.createQuery(SessionImpl.java:1800)
        at org.hibernate.jpa.spi.AbstractEntityManagerImpl.createQuery(AbstractEntityManagerImpl.java:328)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at org.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler.invoke(SharedEntityManagerCreator.java:240)
        at com.sun.proxy.$Proxy68.createQuery(Unknown Source)
        at org.mainco.subco.messaging.repo.MessageDaoImpl.getUnreadClassAnnouncements(MessageDaoImpl.java:161)
        at org.mainco.subco.messaging.repo.MessageDaoImpl.getUnreadMessages(MessageDaoImpl.java:140)
        at org.mainco.subco.messaging.repo.MessageDaoIT.testGetUnreadMessages(MessageDaoIT.java:125)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44)
        at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
        at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41)
        at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
        at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:  74)
        at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:83)
        at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:72)
        at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:231)
        at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:49)
        at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193)
        at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52)
        at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191)
        at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42)
        at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184)
        at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
        at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:71)
        at org.junit.runners.ParentRunner.run(ParentRunner.java:236)
        at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:174)
        at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
        at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
        at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
        at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
        at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
        at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)
    [ERROR]: org.hibernate.hql.internal.ast.ErrorCounter -  Invalid path: 'g.classroom'
    [ERROR]: org.hibernate.hql.internal.ast.ErrorCounter -  Invalid path: 'g.classroom'
     Invalid path: 'g.classroom'
        at org.hibernate.hql.internal.ast.util.LiteralProcessor.lookupConstant(LiteralProcessor.java:129)
        at org.hibernate.hql.internal.ast.tree.DotNode.resolve(DotNode.java:225)
        at org.hibernate.hql.internal.ast.tree.FromReferenceNode.resolve(FromReferenceNode.java:126)
        at org.hibernate.hql.internal.ast.HqlSqlWalker.createFromJoinElement(HqlSqlWalker.java:387)
        at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.joinElement(HqlSqlBaseWalker.java:3903)
        at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.fromElement(HqlSqlBaseWalker.java:3689)
        at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.fromElementList(HqlSqlBaseWalker.java:3567)
        at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.fromClause(HqlSqlBaseWalker.java:708)
        at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.query(HqlSqlBaseWalker.java:564)
        at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.selectStatement(HqlSqlBaseWalker.java:301)
        at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.statement(HqlSqlBaseWalker.java:249)
        at org.hibernate.hql.internal.ast.QueryTranslatorImpl.analyze(QueryTranslatorImpl.java:278)
        at org.hibernate.hql.internal.ast.QueryTranslatorImpl.doCompile(QueryTranslatorImpl.java:206)
        at org.hibernate.hql.internal.ast.QueryTranslatorImpl.compile(QueryTranslatorImpl.java:158)
    …

My message entity is as follows …

@Entity
@Table(name = "msg")
public class Message
{

    @Id
    @NotNull
    @GeneratedValue(generator = "uuid-strategy")
    @Column(name = "ID")
    private String id;

    @Column(name = "MESSAGE", columnDefinition="LONGTEXT")
    private String message;

    @ManyToOne
    @JoinColumn(name = "GROUP_ID", nullable = false, updatable = true)
    private Group group;

And my group entity is as follows …

@Entity
@Table(name = "msg_group")
public class Group
{
    @Id
    @NotNull
    @GeneratedValue(generator = "uuid-strategy")
    @Column(name = "ID")
    private String id;

    @Column(name = "NAME")
    private String name;

    @ManyToOne
    @JoinColumn(name = "CLASSROOM_ID", nullable = true, updatable = true)
    private Classroom classroom;

So why can’t I reference the “classroom” attribute?

Thanks, - Dave

Solution

  • The issue reported by Hibernate is in the first row:

    final String jpqlQuery = "SELECT m FROM Message m LEFT JOIN MessageReadDate mr "...

    in the LEFT JOIN statement. In hql, the JOIN must be expressing the relation, e.g.

    LEFT JOIN m.MessageReadDate mr // the m is referencing the MessageReadDate

    If there is no reference, we can still use that, but with Cartesian product

    FROM Message m, MessageReadDate mr

    in that case, the CROSS JOIN will be issued

    See the:

    small cite:

    Multiple classes can appear, resulting in a cartesian product or "cross" join. 

    from Formula, Parameter
from Formula as form, Parameter as param

    You can also assign aliases to associated entities or to elements of a collection of values using a join. For example: 

    from Cat as cat
    inner join cat.mate as mate