Hi all,

I have a very simple question about queries.

I am trying to run the following query:

from Student student where student.StudentId = " + query.getStudentId()

on the following class mapping:

<class
name="Student"
table="STUDENT"
proxy="Student"
dynamic-update="true"
>

<id
name="StudentId"
type="java.lang.String"
column="STUDENT_ID"
>
<generator class="assigned" />
</id>
<property
name="studentName"
type="java.lang.String"
column="STUDENT_NAME"
not-null="true"
length="100"
/>
<property
name="gender"
type="java.lang.String"
column="GENDER"
length="1"
/>
<property
name="grade"
type="java.lang.String"
column="GRADE"
length="10"
/>
</class>

When I run this query, I get a java.lang.ClassCastException. Am I missing anything here?

THanks.

Stack Trace??!

norc.enum.util.ApplicationException: StudentDelegateImpl createStudent(): Something has gone wrong....java.rmi.ServerException: RemoteException occurred in server thread; nested exception is:
java.rmi.RemoteException: Problem creating Student DAOException: Problem hibernating....net.sf.hibernate.StaleObjectStateException: Row was updated or deleted by another transaction (or unsaved-value mapping was incorrect) for Parent instance with identifier: 9
at delegate.impl.StudentDelegateImpl.createStudent(StudentDelegateImpl.java:71)
at delegate.test.StudentDelegateImplTest.testCreateStudent(StudentDelegateImplTest.java:118)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at junit.framework.TestCase.runTest(TestCase.java:154)
at junit.framework.TestCase.runBare(TestCase.java:127)
at junit.framework.TestResult$1.protect(TestResult.java:106)
at junit.framework.TestResult.runProtected(TestResult.java:124)
at junit.framework.TestResult.run(TestResult.java:109)
at junit.framework.TestCase.run(TestCase.java:118)
at junit.framework.TestSuite.runTest(TestSuite.java:208)
at junit.framework.TestSuite.run(TestSuite.java:203)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:392)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:276)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:167)

ApplicationException: StudentDelegateImplSomething has gone wrong in searching Data....java.rmi.ServerException: RemoteException occurred in server thread; nested exception is:
java.rmi.ServerException: RuntimeException; nested exception is:
java.lang.ClassCastException
at delegate.impl.StudentDelegateImpl.searchData(StudentDelegateImpl.java:121)
at delegate.test.StudentDelegateImplTest.testSearchData(StudentDelegateImplTest.java:154)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at junit.framework.TestCase.runTest(TestCase.java:154)
at junit.framework.TestCase.runBare(TestCase.java:127)
at junit.framework.TestResult$1.protect(TestResult.java:106)
at junit.framework.TestResult.runProtected(TestResult.java:124)
at junit.framework.TestResult.run(TestResult.java:109)
at junit.framework.TestCase.run(TestCase.java:118)
at junit.framework.TestSuite.runTest(TestSuite.java:208)
at junit.framework.TestSuite.run(TestSuite.java:203)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:392)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:276)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:167)

You have not shown us the entire transaction! Please, you MUST provide everything between openSession() and close().

In this case, the problem is something to so with use of "assigned" identifier withunsaved-value="null".

Perhaps you can fix it by using unsaved-value="any".


But what you should do is: go and read the parent/child relationship page of the documentation TWICE before posting again.


Thanks in advance.

String hQuery =
"fromStudent student where student.studentId = " + query.getStudentId();

try {
Session session = HibernateDAOFactory.getSession();
return session.find(hQuery);
} catch (HibernateException e) {
throw new DAOException("Problem in dealing with Hibernate" + e);
}

Based on my mapping above, when I run this query, I get the class exception with the stack trace I showed above. It seems like a simple transaction to test. Thanks.

Two comments:
1) you need a space between from and Student.
2) Although it will work it is best if you use a parameter in the query rather then use the appended string. It allows opportunity for the prepared query to be cached (Hibernate and Database) and reduces object allocation. This helps performance on two levels.

(1) you have shown two different stack traces. One of them is a problem to do with a wong unsaved-value mapping. The second shows an exception occuring in *application code*, not in Hibernate.

(2) the code you *did* show is obviously wrong: "fromStudent student where student.studentId = " is missing a space!

(3) the code you have shown has no cast in it, hence it is not where the class cast exception in the stack trace is coming from!


Hence I conclude that you probably havn't done enough work tracking down the actual source of the exception to be even posting here yet. I suggest you _step_though_your_own_code_ in the debugger to ascertain exactly where the CCE occurs, and then decide what the runtime class is that you are trying to cast to something its not.

This is just basic troubleshooting stuff!

Gavin,

Thanks for your help so far. I am definitely trying to debugg this issue but have not been successful so far. In any case, in point 1 you are right on. But I immediately posted the correct stack track with an explanation in the subject. I thought that kinda explained the issue there. Point 2 is a copy/paste/simplify the code so the focus would be on the issue. There is a space in the the actual query.

Point 3 is what I had the question on. I have no cast in my code. It seems that Hibernate is doing some cast internally. Taking your last piece of advice, I stepped through my code again and dug pretty deep to find that the class net.sf.hibernate.type.IntegerType has a method:
set(PreparedStatement st, Object value, int index) that is called from the following stack of classes/methods:
at net.sf.hibernate.type.NullableType.nullSafeSet(NullableType.java:46)
at net.sf.hibernate.type.NullableType.nullSafeSet(NullableType.java:31)
at net.sf.hibernate.loader.Loader.prepareQueryStatement(Loader.java:494)
at net.sf.hibernate.loader.Loader.doFind(Loader.java:136)
at net.sf.hibernate.loader.Loader.loadEntity(Loader.java:587)
at net.sf.hibernate.loader.EntityLoader.load(EntityLoader.java:42)

set is trying to cast the id I passed it, which is string, to an int.
public void set(PreparedStatement st, Object value, int index)
throws SQLException {
st.setInt(index, ((Integer) value).intValue());
}

The values of the arguments for value and index are "stID1" and index=1. This is where the ClassCastException is taking place:
((Integer) value).intValue() since value is "stID1". Now, given my mapping file and class which specifies that the id is string, why is Hibernate trying to cast the first column value in the resultset (which is has retrieved successfully) to an int when it is actually a String (varchar)? How does it come to think that id is int and not refer to either the mapping file, class, or the resultset metadata to infer that it is dealing with a String?

I would appreciate some more guidance on how to deal with this. Thanks.

I also tried the following code:

String hQuery =
"from Student student where student.studentId =?";

try {
Session session = sessionFactory.openSession();;
Collection c = session.find(hQuery, "stID1", Hibernate.STRING);

Iterator it = c.iterator();

while(it.hasNext()){
System.out.println("Student found " + it.next());
}

} catch (HibernateException e) {
e.printStackTrace();
}

Still got the same stack trace with a CCE.

(1) For future reference when I ask for a stack trace, I mean the WHOLE stack trace! ie. including the stack trace from inside Hibernate. If you swallow the stack trace in your application, it looks to me like the exception occurs in *your* code.

(2) You are not telling me the whole truth! This code:

session.find(hQuery);

ie. A query with no parameters NEVER results in a call to nullSafeSet(), unless there is some association or *something* that is being loaded recursively. However, your mapping document does not show any association. Perhaps you are implementing Lifecycle or something.





Hibernate is doing nothing of the sort! The call to set() is passed a PreparedStatement, not a ResultSet. This is all occurring in prepareQueryStatement, BEFORE a query is executed, and BEFORE there is any result set.

now look at this:



ie. we are inside a *load()*, not a query!. What looks to be happening is that there is some association or something that you havn't told me about. So the first query has successfully executed and now something sparks a second query.


Now, what I need is the whole Hibernate stack trace. Where is the rest of the stack trace, ie. before EntityLoader.load?