Hibernate: org.hibernate.hql.ast.QuerySyntaxException: unexpected token

Question

I am using Hibernate and I have this query:

List<Person> list = sess.createQuery("from Person").list();

With this statement, I get all persons from the database. But now, I only want some persons.

My database scheme:

Project <- Project_Person -> Person

So I only want Persons which are a member of a project.

With the SQL statement on the database I get the desired result:

select * from Person inner join Project_Person 
    on person_id = id 
    where project_id = 1;

So I thought, I can write this with Hibernate:

List<Person> list = 
    sess.createQuery(
        "from Person inner join Project_Person
             on person_id = id 
             where project_id = "+projectId).list();

But here I get an error:

SERVE: Servlet.service() for servlet myproject3 threw exception
org.hibernate.hql.ast.QuerySyntaxException: unexpected token: on near line 1, column 65 [from com.mydomain.myproject.domain.Person inner join Project_Person on person_id = id where project_id = 1]
 at org.hibernate.hql.ast.QuerySyntaxException.convert(QuerySyntaxException.java:54)
 at org.hibernate.hql.ast.QuerySyntaxException.convert(QuerySyntaxException.java:47)
 at org.hibernate.hql.ast.ErrorCounter.throwQueryException(ErrorCounter.java:82)
 at org.hibernate.hql.ast.QueryTranslatorImpl.parse(QueryTranslatorImpl.java:284)
 at org.hibernate.hql.ast.QueryTranslatorImpl.doCompile(QueryTranslatorImpl.java:182)
 at org.hibernate.hql.ast.QueryTranslatorImpl.compile(QueryTranslatorImpl.java:136)
 at org.hibernate.engine.query.HQLQueryPlan.<init>(HQLQueryPlan.java:101)
 at org.hibernate.engine.query.HQLQueryPlan.<init>(HQLQueryPlan.java:80)
 at org.hibernate.engine.query.QueryPlanCache.getHQLQueryPlan(QueryPlanCache.java:124)
 at org.hibernate.impl.AbstractSessionImpl.getHQLQueryPlan(AbstractSessionImpl.java:156)
 at org.hibernate.impl.AbstractSessionImpl.createQuery(AbstractSessionImpl.java:135)
 at org.hibernate.impl.SessionImpl.createQuery(SessionImpl.java:1770)
 at sun.reflect.GeneratedMethodAccessor33.invoke(Unknown Source)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
 at java.lang.reflect.Method.invoke(Method.java:597)
 at org.hibernate.context.ThreadLocalSessionContext$TransactionProtectionWrapper.invoke(ThreadLocalSessionContext.java:344)
 at $Proxy26.createQuery(Unknown Source)
 ...

Does anyone has an idea what's wrong here?

Best Regards.

New Error:

SERVE: Servlet.service() for servlet myproject3 threw exception
org.hibernate.QueryException: could not resolve property: project of: com.mydomain.myproject.domain.Person [from com.mydomain.myproject.domain.Person p where p.project.id = :id]

n:m relation:

@ManyToMany(cascade = CascadeType.ALL)
@JoinTable(name = "Project_Person",
    joinColumns = {@JoinColumn(name="project_id", referencedColumnName="id")},
    inverseJoinColumns = {@JoinColumn(name="person_id", referencedColumnName="id")}
)
private Set<Person> persons = new HashSet<Person>();


@ManyToMany(mappedBy="persons")
private Set<Project> projects = new HashSet<Project>();

Full Error

Hibernate: select project0_.id as id1_, project0_.createDate as create2_1_, project0_.description as descript3_1_, project0_.name as name1_ from Project project0_ where project0_.id=1
Hibernate: select person0_.id as id0_0_, project2_.id as id1_1_, person0_.email as email0_0_, person0_.firstName as firstName0_0_, person0_.lastName as lastName0_0_, project2_.createDate as create2_1_1_, project2_.description as descript3_1_1_, project2_.name as name1_1_ from Person person0_ inner join Project_Person projects1_ on person0_.id=projects1_.person_id inner join Project project2_ on projects1_.project_id=project2_.id where project2_.id=?
15.12.2010 16:42:26 org.apache.catalina.core.ApplicationDispatcher invoke
SERVE: Servlet.service() for servlet myproject3 threw exception
java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to com.mydomain.myproject.domain.Person

Answer 1

HQL queries are written against the object model, not against the database schema.

Therefore your query depends on how you mapped the relationship between persons and projects. For example, in Person has a many-to-one relationship to Project via project property, the query will look like this:

List<Person> list = sess.createQuery(
    "from Person p where p.project.id = :id")
    .setParameter("id", projectId)
    .list();  

EDIT: In the case of many-to-many relationship you need

select p from Person p join p.projects proj where proj.id = :id

Also not that passing parameters via string concatenation is a bad practice, use setParameter() instead.