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From "Unger, Milan" <Milan.Un...@siemens.com>
Subject RE: ejbSelect tutorial?
Date Fri, 20 Oct 2006 08:04:22 GMT
Hello, 

I faced similar problem, the trick to use following EJB QL: 
 
select distinct count(p.key) from Post as p where
p.thread.forum.id=?1

notice count(p.key) - where key should be a property of CMP bean. 
I'm not sure if such syntax is required by EJB spec or simply a bug in
geronimo/open-ejb.

Regards, Milan. 

-----Original Message-----
From: Kaeto23 [mailto:kaeto23@yahoo.de] 
Sent: Thursday, October 19, 2006 6:55 PM
To: Geronimo ML
Subject: ejbSelect tutorial?

Hello,

today I started to work on a CMP that also provides a ejbSelect for
counting some contents from a database. Basically, a CMP named Post
which should count how much entries exist in the database.

Nothing so hard ;)

Anyway, Geronimo has some trouble to use the EJB so I'd like to know
WHAT is the problem :/

Here the code snippet that, when not commented out, makes the trouble:




@XD5EjbSelectMethode(descr = "returns the number of entries", ejbQL =
"select distinct count(p) from Post as p where p.thread.forum.id=?1")
public abstract long ejbSelectForumPostsNum(long forumId) throws
FinderException;



Now XD5 creates the following deployment descriptor entries:

ejb-jar.xml:
...
<query>
	<description>returns the number of entries</description>
	<query-method>
		<method-name>ejbSelectForumPostsNum</method-name>
		<method-params>
			<method-param>long</method-param>
		</method-params>
	</query-method>
	<ejb-ql>select distinct count(p) from Post as p where
p.thread.forum.id=?1</ejb-ql>
</query>
...

openejb-jar.xml
...
<query>
	<query-method>
		<method-name>ejbSelectForumPostsNum</method-name>
		<method-params>
			<method-param>long</method-param>
</method-params>
	</query-method>
	<group-name>Default</group-name>
</query>
...

If these lines are present, Geronimo will crash with this exception:

Caused by: java.lang.ClassCastException: org.tranql.ql.EntityReference
        at
org.tranql.ejbqlcompiler.PathTransformer$Context.<init>(PathTransformer.
java:401)
        at
org.tranql.ejbqlcompiler.PathTransformer$Context.<init>(PathTransformer.
java:380)
        at
org.tranql.ejbqlcompiler.PathTransformer.visit(PathTransformer.java:73)
        at org.tranql.ql.Query.visit(Query.java:59)
        at
org.tranql.ejbqlcompiler.InterRepresentationTransformer.transform(InterR
epresentationTransformer.java:41)
        at
org.tranql.ejbqlcompiler.DerbyEJBQLCompilerFactory$DerbyEJBQLCompiler.tr
ansform(DerbyEJBQLCompilerFactory.java:69)
        at
org.tranql.sql.EJBQLToPhysicalQuery.expandToSQLQuery(EJBQLToPhysicalQuer
y.java:243)
        at
org.tranql.sql.EJBQLToPhysicalQuery.buildSelect(EJBQLToPhysicalQuery.jav
a:171)
        at
org.tranql.sql.EJBQLToPhysicalQuery.buildSelects(EJBQLToPhysicalQuery.ja
va:109)
        at
org.tranql.builder.SQLQueryBuilder.buildSelects(SQLQueryBuilder.java:204
)
        at
org.openejb.deployment.CMPContainerBuilder.buildIt(CMPContainerBuilder.j
ava:311)
        at
org.openejb.deployment.AbstractContainerBuilder.createConfiguration(Abst
ractContainerBuilder.java:354)
        at
org.openejb.deployment.CMPEntityBuilder.createBean(CMPEntityBuilder.java
:213)


So, basically, do you have some examples or tutorials that show the
usage of ejbSelects with Geronimo 1.1.1? Let me know :)

Best regards

Dirk


	

	
		
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