@Cache annotation usage error

问题:

I added the following annotation to enable cache to one of my EJB3 entities, to test caching with ehCache, where I use Hibernate as the persistence provider:

....
import org.hibernate.annotations.Cache;
import org.hibernate.annotations.CacheConcurrencyStrategy;

@Entity
@Table(name = "F")
@Cache(usage=CacheConcurrencyStrategy.READ_WRITE)
@NamedQueries({ @NamedQuery(name = "F.findAll", query = "SELECT f FROM F f")})
public class F implements Serializable {
   .....
}

I added the following to persistence.xml:

<property name="hibernate.cache.provider_class" value="org.hibernate.cache.EhCacheProvider"/>
<property name="hibernate.cache.provider_configuration_file_resource_path" value="/ehcache.xml"/>
<property name="hibernate.cache.use_second_level_cache" value="true"/>

And when I try to compile I get the following error:

/persistence/F.class): warning: Cannot find annotation method 'usage()' in type 'org.hibernate.annotations.Cache': class file for org.hibernate.annotations.Cache not found An exception has occurred in the compiler (1.6.0_16). Please file a bug at the Java Developer Connection (http://java.sun.com/webapps/bugreport) after checking the Bug Parade for duplicates. Include your program and the following diagnostic in your report. Thank you. com.sun.tools.javac.code.Symbol$CompletionFailure: class file for org.hibernate.annotations.CacheConcurrencyStrategy not found

Can anyone help me out here and let me know what I need to do or am doing wrong currently ?

回答1:

@org.hibernate.annotations.Cache(usage = org.hibernate.annotations.CacheConcurrencyStrategy.READ_WRITE)

will solve the problem

回答2:

Well .. I got it to work eventually. The fix for it is really strange and really does seem to be a reported bug.

What I needed to do was to add all the Hibernate libraries to my Netbeans web/war project as well. Once I did that, the errors went away.

This was strange because the Hibernate libraries were already included in the ear project which was also in the web project library.

回答3:

You're not doing anything wrong - your annotations are fine.

Judging by the error message it's a compiler bug. You can:

1. Update to the latest JDK version (1.6.0_16-b01).
2. Rearrange your annotations and hope that compiler bug will not be triggered. Yes, that sounds silly but I have used @Cache declarations extensively (as I'm sure many other people did) and I have no problems with compilation meaning you just got (un)lucky.
3. Try a different compiler (build from Eclipse)
4. Submit a bug report to Sun.

回答4:

You only have to add hibernate-annotations jars to your web/war project.

回答5:

I solved this by changing the hibernate libraries from provided to compile in the pom of a maven multi module project.