title: Could not resolve a persistence unit error - Netbeans 7.3/7.4 and Glassfish 4
body: <p>I've been adapting a code sample from the JSF2.0 Complete Reference textbook (the Virtual Trainer application) to run using CDI. All was going well until I started adding some of the JSF code at which point the deployment began to repeatedly fail stating that it could not resolve a persistence unit. I was somewhat puzzled as I hadn't touched any of my entity code or controller beans but rolled the application back anyway (manually - I didn't have it attached to Subversion a the time). Despite this, the error persists so something has changed but I can't find it! Others have reported an identical error that was associated with a misplaced persistence.xml file but my copy seems to be deployed correctly as far as I can tell.</p>
  
  <p>The project is based on a Maven Java EE Web Archetype and I'm using Netbeans 7.4 (final), Java EE7 and Glassfish 4. It's also worth noting that as I started to write some JSF pages, Netbeans seemed to develop hiccups as it didn't recognise some of the tags (e.g. ) so I suspect there is a bug there.</p>
  
  <p>I'd be really grateful if anyone has any ideas!</p>
  
  <p>Stacktrace as follows:</p>
  
  <pre><code>SEVERE:   Exception while invoking class org.glassfish.persistence.jpa.JPADeployer prepare method
  SEVERE:   java.lang.RuntimeException: Could not resolve a persistence unit corresponding to the persistence-context-ref-name [com.sun.ejb.containers.TimerBean/em] in the scope of the module called [trainer]. Please verify your application.
      at com.sun.enterprise.deployment.BundleDescriptor.findReferencedPUViaEMRef(BundleDescriptor.java:727)
      at com.sun.enterprise.deployment.BundleDescriptor.findReferencedPUsViaPCRefs(BundleDescriptor.java:715)
      at org.glassfish.web.deployment.descriptor.WebBundleDescriptorImpl.findReferencedPUs(WebBundleDescriptorImpl.java:996)
      at org.glassfish.persistence.jpa.JPADeployer.createEMFs(JPADeployer.java:186)
      at org.glassfish.persistence.jpa.JPADeployer.prepare(JPADeployer.java:168)
      at com.sun.enterprise.v3.server.ApplicationLifecycle.prepareModule(ApplicationLifecycle.java:922)
      at com.sun.enterprise.v3.server.ApplicationLifecycle.deploy(ApplicationLifecycle.java:431)
      at com.sun.enterprise.v3.server.ApplicationLifecycle.deploy(ApplicationLifecycle.java:219)
      at org.glassfish.deployment.admin.DeployCommand.execute(DeployCommand.java:491)
      at com.sun.enterprise.v3.admin.CommandRunnerImpl$2$1.run(CommandRunnerImpl.java:527)
      at com.sun.enterprise.v3.admin.CommandRunnerImpl$2$1.run(CommandRunnerImpl.java:523)
      at java.security.AccessController.doPrivileged(Native Method)
      at javax.security.auth.Subject.doAs(Subject.java:356)
      at com.sun.enterprise.v3.admin.CommandRunnerImpl$2.execute(CommandRunnerImpl.java:522)
      at com.sun.enterprise.v3.admin.CommandRunnerImpl.doCommand(CommandRunnerImpl.java:546)
      at com.sun.enterprise.v3.admin.CommandRunnerImpl.doCommand(CommandRunnerImpl.java:1423)
      at com.sun.enterprise.v3.admin.CommandRunnerImpl.access$1500(CommandRunnerImpl.java:108)
      at com.sun.enterprise.v3.admin.CommandRunnerImpl$ExecutionContext.execute(CommandRunnerImpl.java:1762)
      at com.sun.enterprise.v3.admin.CommandRunnerImpl$ExecutionContext.execute(CommandRunnerImpl.java:1674)
      at com.sun.enterprise.v3.admin.AdminAdapter.doCommand(AdminAdapter.java:534)
      at com.sun.enterprise.v3.admin.AdminAdapter.onMissingResource(AdminAdapter.java:224)
      at org.glassfish.grizzly.http.server.StaticHttpHandler.service(StaticHttpHandler.java:297)
      at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:246)
      at org.glassfish.grizzly.http.server.HttpHandler.runService(HttpHandler.java:191)
      at org.glassfish.grizzly.http.server.HttpHandler.doHandle(HttpHandler.java:168)
      at org.glassfish.grizzly.http.server.HttpServerFilter.handleRead(HttpServerFilter.java:189)
      at org.glassfish.grizzly.filterchain.ExecutorResolver$9.execute(ExecutorResolver.java:119)
      at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter(DefaultFilterChain.java:288)
      at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart(DefaultFilterChain.java:206)
      at org.glassfish.grizzly.filterchain.DefaultFilterChain.execute(DefaultFilterChain.java:136)
      at org.glassfish.grizzly.filterchain.DefaultFilterChain.process(DefaultFilterChain.java:114)
      at org.glassfish.grizzly.ProcessorExecutor.execute(ProcessorExecutor.java:77)
      at org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent(TCPNIOTransport.java:838)
      at org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent(AbstractIOStrategy.java:113)
      at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0(WorkerThreadIOStrategy.java:115)
      at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access$100(WorkerThreadIOStrategy.java:55)
      at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy$WorkerThreadRunnable.run(WorkerThreadIOStrategy.java:135)
      at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:564)
      at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:544)
      at java.lang.Thread.run(Thread.java:724)
  SEVERE:   Exception while preparing the app
  SEVERE:   Exception during lifecycle processing
  java.lang.RuntimeException: Could not resolve a persistence unit corresponding to the persistence-context-ref-name [com.sun.ejb.containers.TimerBean/em] in the scope of the module called [trainer]. Please verify your application.
      at com.sun.enterprise.deployment.BundleDescriptor.findReferencedPUViaEMRef(BundleDescriptor.java:727)
      at com.sun.enterprise.deployment.BundleDescriptor.findReferencedPUsViaPCRefs(BundleDescriptor.java:715)
      at org.glassfish.web.deployment.descriptor.WebBundleDescriptorImpl.findReferencedPUs(WebBundleDescriptorImpl.java:996)
      at org.glassfish.persistence.jpa.JPADeployer.createEMFs(JPADeployer.java:186)
      at org.glassfish.persistence.jpa.JPADeployer.prepare(JPADeployer.java:168)
      at com.sun.enterprise.v3.server.ApplicationLifecycle.prepareModule(ApplicationLifecycle.java:922)
      at com.sun.enterprise.v3.server.ApplicationLifecycle.deploy(ApplicationLifecycle.java:431)
      at com.sun.enterprise.v3.server.ApplicationLifecycle.deploy(ApplicationLifecycle.java:219)
      at org.glassfish.deployment.admin.DeployCommand.execute(DeployCommand.java:491)
      at com.sun.enterprise.v3.admin.CommandRunnerImpl$2$1.run(CommandRunnerImpl.java:527)
      at com.sun.enterprise.v3.admin.CommandRunnerImpl$2$1.run(CommandRunnerImpl.java:523)
      at java.security.AccessController.doPrivileged(Native Method)
      at javax.security.auth.Subject.doAs(Subject.java:356)
      at com.sun.enterprise.v3.admin.CommandRunnerImpl$2.execute(CommandRunnerImpl.java:522)
      at com.sun.enterprise.v3.admin.CommandRunnerImpl.doCommand(CommandRunnerImpl.java:546)
      at com.sun.enterprise.v3.admin.CommandRunnerImpl.doCommand(CommandRunnerImpl.java:1423)
      at com.sun.enterprise.v3.admin.CommandRunnerImpl.access$1500(CommandRunnerImpl.java:108)
      at com.sun.enterprise.v3.admin.CommandRunnerImpl$ExecutionContext.execute(CommandRunnerImpl.java:1762)
      at com.sun.enterprise.v3.admin.CommandRunnerImpl$ExecutionContext.execute(CommandRunnerImpl.java:1674)
      at com.sun.enterprise.v3.admin.AdminAdapter.doCommand(AdminAdapter.java:534)
      at com.sun.enterprise.v3.admin.AdminAdapter.onMissingResource(AdminAdapter.java:224)
      at org.glassfish.grizzly.http.server.StaticHttpHandler.service(StaticHttpHandler.java:297)
      at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:246)
      at org.glassfish.grizzly.http.server.HttpHandler.runService(HttpHandler.java:191)
      at org.glassfish.grizzly.http.server.HttpHandler.doHandle(HttpHandler.java:168)
      at org.glassfish.grizzly.http.server.HttpServerFilter.handleRead(HttpServerFilter.java:189)
      at org.glassfish.grizzly.filterchain.ExecutorResolver$9.execute(ExecutorResolver.java:119)
      at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter(DefaultFilterChain.java:288)
      at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart(DefaultFilterChain.java:206)
      at org.glassfish.grizzly.filterchain.DefaultFilterChain.execute(DefaultFilterChain.java:136)
      at org.glassfish.grizzly.filterchain.DefaultFilterChain.process(DefaultFilterChain.java:114)
      at org.glassfish.grizzly.ProcessorExecutor.execute(ProcessorExecutor.java:77)
      at org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent(TCPNIOTransport.java:838)
      at org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent(AbstractIOStrategy.java:113)
      at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0(WorkerThreadIOStrategy.java:115)
      at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access$100(WorkerThreadIOStrategy.java:55)
      at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy$WorkerThreadRunnable.run(WorkerThreadIOStrategy.java:135)
      at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:564)
      at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:544)
      at java.lang.Thread.run(Thread.java:724)
  </code></pre>
  
  <p>Persistence.xml (exploded file location: trainer/target/classes/META-INF/)
  File was not changed at the time the error occurred but I recreated the file to be sure)</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;persistence version="2.1" xmlns="http://xmlns.jcp.org/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd"&gt;
    &lt;persistence-unit name="Trainer_PU" transaction-type="JTA"&gt;
      &lt;provider&gt;org.eclipse.persistence.jpa.PersistenceProvider&lt;/provider&gt;
      &lt;jta-data-source&gt;jdbc/myDatasource&lt;/jta-data-source&gt;
      &lt;exclude-unlisted-classes&gt;false&lt;/exclude-unlisted-classes&gt;
      &lt;properties&gt;
        &lt;property name="javax.persistence.schema-generation.database.action" value="drop-and-create"/&gt;
      &lt;/properties&gt;
    &lt;/persistence-unit&gt;
  &lt;/persistence&gt;
  </code></pre>