Hi, I've implemented a custom resource using ResourceProvider SPI and a custom JPA entity using JpaEntityProvider SPI. If I try to import a EntityManager inside my custom resource, using: EntityManager em = session.getProvider(JpaConnectionProvider.class) .getEntityManager(); When I try to access, I receive the following error: *Stack Trace* java.lang.NoClassDefFoundError: javax/persistence/EntityManager java.lang.Class.getDeclaredMethods0(Native Method) java.lang.Class.privateGetDeclaredMethods(Class.java:2701) java.lang.Class.getDeclaredMethods(Class.java:1975) org.jboss.resteasy.util.GetRestful.hasJAXRSAnnotations(GetRestful.java:109) org.jboss.resteasy.util.GetRestful.isSubResourceClass(GetRestful.java:38) org.jboss.resteasy.core.ResourceLocatorInvoker.invokeOnTargetObject(ResourceLocatorInvoker.java:121) org.jboss.resteasy.core.ResourceLocatorInvoker.invoke(ResourceLocatorInvoker.java:101) org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:395) org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:202) org.jboss.resteasy.plugins.server.servlet.ServletContainerDispatcher.service(ServletContainerDispatcher.java:221) org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher.service(HttpServletDispatcher.java:56) org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher.service(HttpServletDispatcher.java:51) javax.servlet.http.HttpServlet.service(HttpServlet.java:790) io.undertow.servlet.handlers.ServletHandler.handleRequest(ServletHandler.java:85) io.undertow.servlet.handlers.FilterHandler$FilterChainImpl.doFilter(FilterHandler.java:129) org.keycloak.services.filters.KeycloakSessionServletFilter.doFilter(KeycloakSessionServletFilter.java:90) io.undertow.servlet.core.ManagedFilter.doFilter(ManagedFilter.java:60) io.undertow.servlet.handlers.FilterHandler$FilterChainImpl.doFilter(FilterHandler.java:131) io.undertow.servlet.handlers.FilterHandler.handleRequest(FilterHandler.java:84) io.undertow.servlet.handlers.security.ServletSecurityRoleHandler.handleRequest(ServletSecurityRoleHandler.java:62) io.undertow.servlet.handlers.ServletDispatchingHandler.handleRequest(ServletDispatchingHandler.java:36) org.wildfly.extension.undertow.security.SecurityContextAssociationHandler.handleRequest(SecurityContextAssociationHandler.java:78) io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43) io.undertow.servlet.handlers.security.SSLInformationAssociationHandler.handleRequest(SSLInformationAssociationHandler.java:131) io.undertow.servlet.handlers.security.ServletAuthenticationCallHandler.handleRequest(ServletAuthenticationCallHandler.java:57) io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43) io.undertow.security.handlers.AbstractConfidentialityHandler.handleRequest(AbstractConfidentialityHandler.java:46) io.undertow.servlet.handlers.security.ServletConfidentialityConstraintHandler.handleRequest(ServletConfidentialityConstraintHandler.java:64) io.undertow.security.handlers.AuthenticationMechanismsHandler.handleRequest(AuthenticationMechanismsHandler.java:60) io.undertow.servlet.handlers.security.CachedAuthenticatedSessionHandler.handleRequest(CachedAuthenticatedSessionHandler.java:77) io.undertow.security.handlers.NotificationReceiverHandler.handleRequest(NotificationReceiverHandler.java:50) io.undertow.security.handlers.AbstractSecurityContextAssociationHandler.handleRequest(AbstractSecurityContextAssociationHandler.java:43) io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43) org.wildfly.extension.undertow.security.jacc.JACCContextIdHandler.handleRequest(JACCContextIdHandler.java:61) io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43) io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43) io.undertow.servlet.handlers.ServletInitialHandler.handleFirstRequest(ServletInitialHandler.java:284) io.undertow.servlet.handlers.ServletInitialHandler.dispatchRequest(ServletInitialHandler.java:263) io.undertow.servlet.handlers.ServletInitialHandler.access$000(ServletInitialHandler.java:81) io.undertow.servlet.handlers.ServletInitialHandler$1.handleRequest(ServletInitialHandler.java:174) io.undertow.server.Connectors.executeRootHandler(Connectors.java:202) io.undertow.server.HttpServerExchange$1.run(HttpServerExchange.java:793) java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) java.lang.Thread.run(Thread.java:745) If I remove the EntityManager code, the resource works fine. Any ideas? Thanks, Bruno