EntityManager can't see mapped classes in jar file

I have a set of annotated entity classes that live in a common.jar file. I'm able to build a .war file which references this common.jar, and to generate ddl via hbm2ddl. When I deploy the resulting .war file, though, the EntityManager isn't able to find mappings for any of my classes resulting in errors like the one below.

I have tried including the .jar within the .war, placing the .jar into the server/default/lib directory, referencing it from another common location, and many variations along the way all without success.

Any pointers would be very, very welcome. I had thought I was home free when the build succeeded but obviously I'm still missing a piece somewhere.

Note: If I move the source for these classes into the .war project, then it works perfectly, but I'd like to keep these separate for various reasons.

2011-02-22 04:36:26,939 ERROR [org.jboss.seam.exception.Exceptions] (http-0.0.0.0-8080-11) handled and logged exception
javax.servlet.ServletException: org.jboss.resteasy.spi.UnhandledException: java.lang.IllegalArgumentException: Unknown entity: com.techma.aoio.model.Message
    at org.jboss.seam.servlet.ContextualHttpServletRequest.run(ContextualHttpServletRequest.java:74)
    at org.jboss.seam.resteasy.ResteasyResourceAdapter.getResource(ResteasyResourceAdapter.java:121)
    at org.jboss.seam.servlet.SeamResourceServlet.service(SeamResourceServlet.java:80)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:83)
    at org.jboss.seam.web.IdentityFilter.doFilter(IdentityFilter.java:40)
    at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69)
    at org.jboss.seam.web.MultipartFilter.doFilter(MultipartFilter.java:90)
    at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69)
    at org.jboss.seam.web.ExceptionFilter.doFilter(ExceptionFilter.java:64)
    at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69)
    at org.jboss.seam.web.RedirectFilter.doFilter(RedirectFilter.java:45)
    at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69)
    at org.ajax4jsf.webapp.BaseXMLFilter.doXmlFilter(BaseXMLFilter.java:178)
    at org.ajax4jsf.webapp.BaseFilter.handleRequest(BaseFilter.java:290)
    at org.ajax4jsf.webapp.BaseFilter.processUploadsAndHandleRequest(BaseFilter.java:368)
    at org.ajax4jsf.webapp.BaseFilter.doFilter(BaseFilter.java:495)
    at org.jboss.seam.web.Ajax4jsfFilter.doFilter(Ajax4jsfFilter.java:56)
    at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69)
    at org.jboss.seam.web.LoggingFilter.doFilter(LoggingFilter.java:60)
    at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69)
    at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:73)
    at org.jboss.seam.servlet.SeamFilter.doFilter(SeamFilter.java:158)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(A开发者_Python百科pplicationFilterChain.java:235)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:235)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
    at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:190)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:433)
    at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:92)
    at org.jboss.web.tomcat.security.SecurityContextEstablishmentValve.process(SecurityContextEstablishmentValve.java:126)
    at org.jboss.web.tomcat.security.SecurityContextEstablishmentValve.invoke(SecurityContextEstablishmentValve.java:70)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
    at org.jboss.web.tomcat.service.jca.CachedConnectionValve.invoke(CachedConnectionValve.java:158)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:330)
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:829)
    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:598)
    at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
    at java.lang.Thread.run(Thread.java:619)
Caused by: org.jboss.resteasy.spi.UnhandledException: java.lang.IllegalArgumentException: Unknown entity: com.techma.aoio.model.Message
    at org.jboss.resteasy.core.SynchronousDispatcher.handleApplicationException(SynchronousDispatcher.java:296)
    at org.jboss.resteasy.core.SynchronousDispatcher.handleException(SynchronousDispatcher.java:208)
    at org.jboss.resteasy.core.SynchronousDispatcher.handleInvokerException(SynchronousDispatcher.java:187)
    at org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:371)
    at org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:160)
    at org.jboss.seam.resteasy.ResteasyResourceAdapter$1.process(ResteasyResourceAdapter.java:145)
    at org.jboss.seam.servlet.ContextualHttpServletRequest.run(ContextualHttpServletRequest.java:53)
    ... 45 more
Caused by: java.lang.IllegalArgumentException: Unknown entity: com.techma.aoio.model.Message
    at org.hibernate.ejb.AbstractEntityManagerImpl.find(AbstractEntityManagerImpl.java:193)
    at org.jboss.seam.persistence.EntityManagerProxy.find(EntityManagerProxy.java:87)
    at com.techma.tng.resources.MessageResource.get(MessageResource.java:72)
    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.jboss.seam.util.Reflections.invoke(Reflections.java:22)
    at org.jboss.seam.intercept.RootInvocationContext.proceed(RootInvocationContext.java:32)
    at org.jboss.seam.intercept.SeamInvocationContext.proceed(SeamInvocationContext.java:56)
    at org.jboss.seam.resteasy.ResteasyContextInjectionInterceptor.aroundInvoke(ResteasyContextInjectionInterceptor.java:59)
    at org.jboss.seam.intercept.SeamInvocationContext.proceed(SeamInvocationContext.java:68)
    at org.jboss.seam.transaction.RollbackInterceptor.aroundInvoke(RollbackInterceptor.java:28)
    at org.jboss.seam.intercept.SeamInvocationContext.proceed(SeamInvocationContext.java:68)
    at org.jboss.seam.core.BijectionInterceptor.aroundInvoke(BijectionInterceptor.java:77)
    at org.jboss.seam.intercept.SeamInvocationContext.proceed(SeamInvocationContext.java:68)
    at org.jboss.seam.transaction.TransactionInterceptor$1.work(TransactionInterceptor.java:97)
    at org.jboss.seam.util.Work.workInTransaction(Work.java:47)
    at org.jboss.seam.transaction.TransactionInterceptor.aroundInvoke(TransactionInterceptor.java:91)
    at org.jboss.seam.intercept.SeamInvocationContext.proceed(SeamInvocationContext.java:68)
    at org.jboss.seam.core.MethodContextInterceptor.aroundInvoke(MethodContextInterceptor.java:44)
    at org.jboss.seam.intercept.SeamInvocationContext.proceed(SeamInvocationContext.java:68)
    at org.jboss.seam.intercept.RootInterceptor.invoke(RootInterceptor.java:107)
    at org.jboss.seam.intercept.JavaBeanInterceptor.interceptInvocation(JavaBeanInterceptor.java:185)
    at org.jboss.seam.intercept.JavaBeanInterceptor.invoke(JavaBeanInterceptor.java:103)
    at com.techma.tng.resources.MessageResource_$$_javassist_seam_4.get(MessageResource_$$_javassist_seam_4.java)
    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.jboss.resteasy.core.MethodInjectorImpl.invoke(MethodInjectorImpl.java:119)
    at org.jboss.resteasy.core.ResourceMethod.invokeOnTarget(ResourceMethod.java:211)
    at org.jboss.resteasy.core.ResourceMethod.invoke(ResourceMethod.java:176)
    at org.jboss.resteasy.core.ResourceMethod.invoke(ResourceMethod.java:166)
    at org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:356)
    ... 48 more
Caused by: org.hibernate.MappingException: Unknown entity: com.techma.aoio.model.Message
    at org.hibernate.impl.SessionFactoryImpl.getEntityPersister(SessionFactoryImpl.java:580)
    at org.hibernate.event.def.DefaultLoadEventListener.onLoad(DefaultLoadEventListener.java:91)
    at org.hibernate.impl.SessionImpl.fireLoad(SessionImpl.java:905)
    at org.hibernate.impl.SessionImpl.get(SessionImpl.java:842)
    at org.hibernate.impl.SessionImpl.get(SessionImpl.java:835)
    at org.hibernate.ejb.AbstractEntityManagerImpl.find(AbstractEntityManagerImpl.java:182)
    ... 82 more

Thanks to axtavt pointing me to a duplicate, I was able to determine that including a <jar-file>file:/opt/lib/common.jar</jar-file> tag in my persistence.xml was all that was required to let hibernate see the mapped classes. Thanks!