我刚刚升级到 GAE SDK 1.7.1，现在我正在尝试在我的 [前] 功能项目中使用 JPA 2。当我尝试使用实体管理器时，它会引发以下异常：
java.lang.ExceptionInInitializerError
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:169)
at com.google.appengine.tools.development.agent.runtime.RuntimeHelper.checkRestricted(RuntimeHelper.java:69)
at com.google.appengine.tools.development.agent.runtime.Runtime.checkRestricted(Runtime.java:64)
at com.olympya.futweb.ServicesServlet.doPost(ServicesServlet.java:39)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)
at com.google.appengine.tools.appstats.AppstatsFilter.doFilter(AppstatsFilter.java:141)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.appengine.tools.development.HeaderVerificationFilter.doFilter(HeaderVerificationFilter.java:35)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.appengine.api.blobstore.dev.ServeBlobFilter.doFilter(ServeBlobFilter.java:60)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter(TransactionCleanupFilter.java:43)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.appengine.tools.development.StaticFileFilter.doFilter(StaticFileFilter.java:125)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.appengine.tools.development.BackendServersFilter.doFilter(BackendServersFilter.java:97)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)
at com.google.appengine.tools.development.DevAppEngineWebAppContext.handle(DevAppEngineWebAppContext.java:94)
at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
at com.google.appengine.tools.development.JettyContainerService$ApiProxyHandler.handle(JettyContainerService.java:370)
at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
at org.mortbay.jetty.Server.handle(Server.java:326)
at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
at org.mortbay.jetty.HttpConnection$RequestHandler.content(HttpConnection.java:938)
at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:755)
at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:218)
at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:409)
at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582)
Caused by: javax.persistence.PersistenceException: Explicit persistence provider error(s) occurred for "transactions-optional" after trying the following discovered implementations: org.datanucleus.api.jpa.PersistenceProviderImpl from provider: org.datanucleus.api.jpa.PersistenceProviderImpl
at javax.persistence.Persistence.createPersistenceException(Persistence.java:242)
at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:184)
at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:70)
at com.olympya.futweb.datamodel.EMHelper.<clinit>(EMHelper.java:49)
... 38 more
Caused by: org.datanucleus.exceptions.NucleusUserException: Errors were encountered when loading the MetaData for the persistence-unit "transactions-optional". See the nested exceptions for details
at org.datanucleus.metadata.MetaDataManager.loadPersistenceUnit(MetaDataManager.java:979)
at org.datanucleus.api.jpa.JPAEntityManagerFactory.initialiseNucleusContext(JPAEntityManagerFactory.java:754)
at org.datanucleus.api.jpa.JPAEntityManagerFactory.initialise(JPAEntityManagerFactory.java:417)
at org.datanucleus.api.jpa.JPAEntityManagerFactory.<init>(JPAEntityManagerFactory.java:380)
at org.datanucleus.api.jpa.PersistenceProviderImpl.createEntityManagerFactory(PersistenceProviderImpl.java:91)
at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:150)
... 40 more
Caused by: java.security.AccessControlException: access denied (java.lang.RuntimePermission accessClassInPackage.sun.reflect.generics.reflectiveObjects)
at java.security.AccessControlContext.checkPermission(AccessControlContext.java:374)
at java.security.AccessController.checkPermission(AccessController.java:546)
at java.lang.SecurityManager.checkPermission(SecurityManager.java:532)
at com.google.appengine.tools.development.DevAppServerFactory$CustomSecurityManager.checkPermission(DevAppServerFactory.java:283)
at java.lang.SecurityManager.checkPackageAccess(SecurityManager.java:1512)
at java.lang.ClassLoader$1.run(ClassLoader.java:330)
at java.security.AccessController.doPrivileged(Native Method)
at java.lang.ClassLoader.checkPackageAccess(ClassLoader.java:328)
at java.lang.Class.getDeclaredMethods0(Native Method)
at java.lang.Class.privateGetDeclaredMethods(Class.java:2427)
at java.lang.Class.getDeclaredMethods(Class.java:1791)
at org.datanucleus.metadata.annotations.AbstractAnnotationReader.getJavaBeanAccessorAnnotationsForClass(AbstractAnnotationReader.java:310)
at org.datanucleus.metadata.annotations.AbstractAnnotationReader.getMetaDataForClass(AbstractAnnotationReader.java:146)
at org.datanucleus.metadata.annotations.AnnotationManagerImpl.getMetaDataForClass(AnnotationManagerImpl.java:171)
at org.datanucleus.metadata.MetaDataManager.loadAnnotationsForClass(MetaDataManager.java:2650)
at org.datanucleus.metadata.MetaDataManager.loadPersistenceUnit(MetaDataManager.java:955)
... 45 more
我的 persistence.xml 是这样的：
<?xml version="1.0" encoding="UTF-8" ?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence
http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd" version="1.0">
<persistence-unit name="transactions-optional">
<provider>org.datanucleus.api.jpa.PersistenceProviderImpl</provider>
<properties>
<property name="datanucleus.NontransactionalRead" value="true"/>
<property name="datanucleus.NontransactionalWrite" value="true"/>
<property name="datanucleus.ConnectionURL" value="appengine"/>
<property name="datanucleus.appengine.multipleRelationsOfSameTypeAreErrors" value="false"/>
<property name="datanucleus.DetachAllOnCommit" value="false"/>
<property name="datanucleus.DetachOnClose" value="true"/>
<property name="datanucleus.appengine.datastoreEnableXGTransactions" value="true"/>
</properties>
</persistence-unit>
</persistence>
我的助手是这样的：
public final class EMHelper
{
private static final EMHelper emhInstance = new EMHelper();
private static final EntityManagerFactory emfInstance =
Persistence.createEntityManagerFactory("transactions-optional");
private EMHelper()
{
}
public static EMHelper getInstance()
{
return emhInstance;
}
public static EntityManager getEntityManager()
{
return emfInstance.createEntityManager();
}
...