首次连接数据库时，NullPointer在日志中
我第一次使用createEntityManager()连接到数据库时，在tomcat的控制台上出现NullPointerException 。 我在用：
- apache tomcat 8.0.24
- eclipselink 2.6.1-RC1（JPA间接使用）
- sqlite jdbc 3.8.10.1
日志消息如下：
[EL Warning]: connection: 2015-08-21 16:01:51.569--java.lang.NullPointerException [EL Info]: 2015-08-21 16:01:51.585--ServerSession(29156874)--EclipseLink, version: Eclipse Persistence Services - 2.6.1.v20150605-31e8258 [EL Info]: connection: 2015-08-21 16:01:52.365--Not able to detect platform for vendor name [SQLite33.8.10.1]. Defaulting to [org.eclipse.persistence.platform.database.DatabasePlatform]. The database dialect used may not match with the database you are using. Please explicitly provide a platform using property "eclipselink.target-database". [EL Info]: connection: 2015-08-21 16:01:52.505--ServerSession(29156874)--/file:/C:/eclipse_ee/workspaces/.metadata/.plugins/org.eclipse.wst.server.core/tmp0/wtpwebapps/jeejpa/WEB-INF/classes/_training-jpa login successful
我的应用程序似乎工作正常 – 我是否必须关心有关NullPointerException的警告 ？ 或者我是否需要关心这些信息 ？
Not able to detect platform for vendor name [SQLite33.8.10.1]. Defaulting to [org.eclipse.persistence.platform.database.DatabasePlatform]. The database dialect used may not match with the database you are using. Please explicitly provide a platform using property "eclipselink.target-database".
编辑：感谢@baumato的帮助和设置关于无法检测的信息……不再显示。 详细的NullPointerException现在是：
[EL Finest]: jpa: 2015-08-21 16:44:52.954--ServerSession(12993102)--Thread(Thread[http-nio-8443-exec-6,5,main])--Begin deploying Persistence Unit training-jpa; session /file:/C:/eclipse_ee/workspaces/.metadata/.plugins/org.eclipse.wst.server.core/tmp0/wtpwebapps/jeejpa/WEB-INF/classes/_training-jpa; state Predeployed; factoryCount 1 [EL Finest]: jpa: 2015-08-21 16:44:52.964--ServerSession(12993102)--Thread(Thread[http-nio-8443-exec-6,5,main])--Bean Validation Factory was not initialized: [javax/validation/Validation]. [EL Warning]: connection: 2015-08-21 16:44:52.974--Thread(Thread[http-nio-8443-exec-6,5,main])--java.lang.NullPointerException at org.eclipse.persistence.platform.server.ServerPlatformUtils.createServerPlatform(ServerPlatformUtils.java:99) at org.eclipse.persistence.sessions.factories.SessionManager.init(SessionManager.java:77) at org.eclipse.persistence.sessions.factories.SessionManager.(SessionManager.java:71) at org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.addSessionToGlobalSessionManager(EntityManagerSetupImpl.java:907) at org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.initSession(EntityManagerSetupImpl.java:2671) at org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.deploy(EntityManagerSetupImpl.java:675) at org.eclipse.persistence.internal.jpa.EntityManagerFactoryDelegate.getAbstractSession(EntityManagerFactoryDelegate.java:205) at org.eclipse.persistence.internal.jpa.EntityManagerFactoryDelegate.createEntityManagerImpl(EntityManagerFactoryDelegate.java:305) at org.eclipse.persistence.internal.jpa.EntityManagerFactoryImpl.createEntityManagerImpl(EntityManagerFactoryImpl.java:337) at org.eclipse.persistence.internal.jpa.EntityManagerFactoryImpl.createEntityManager(EntityManagerFactoryImpl.java:303) at de.training.beans.LoginBean.login(LoginBean.java:58) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:483) at org.apache.el.parser.AstValue.invoke(AstValue.java:247) at org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:267) at com.sun.faces.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:105) at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:87) at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:102) at javax.faces.component.UICommand.broadcast(UICommand.java:315) at javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:790) at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1282) at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:81) at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101) at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:198) at javax.faces.webapp.FacesServlet.service(FacesServlet.java:654) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at de.training.filter.URILoggerFilter.doFilter(URILoggerFilter.java:24) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at de.training.filter.LoginFilter.doFilter(LoginFilter.java:38) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:614) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:617) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:518) at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1091) at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:668) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1527) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1484) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.lang.Thread.run(Thread.java:745) [EL Finer]: 2015-08-21 16:44:52.974--Thread(Thread[http-nio-8443-exec-6,5,main])--initializing session manager
此exception与数据库平台无关，而与应用程序服务器平台有关。 这不是致命的。 SessionManager #init（）方法执行以下操作：
String platformClass = ServerPlatformUtils.detectServerPlatform(null); try { detectedPlatform = ServerPlatformUtils.createServerPlatform( null, platformClass, SessionManager.class.getClassLoader()); } catch (NullPointerException npe) { //some platforms may not be handling 'null' session well, //so be defensive here and only log throwable here detectedPlatform = null; LOG.logThrowable(SessionLog.WARNING, AbstractSessionLog.CONNECTION, npe); }
因此null用作检测到的服务器平台，EclipseLink将认为当前的应用程序服务器平台没有多租户支持（Apache Tomcat没有）。 SessionManager中的此代码与新的WebLogicfunction相关，您可以忽略它。 2.7.0抛出ServerPlatformException而不是NPE，但是这个更改没有被引入2.6.1。
如果你们想添加Apache Tomcat平台检测，请在Eclipselink Bugzilla上打开增强请求并投票给它优先级。
我建议在persistence.xml的属性部分添加以下属性以获取详细的调试信息：
并且正如信息消息所述，尝试设置属性：
由于“自动”是默认值，因此可能无济于事。 因此，将目标数据库设置为“数据库”。 如果未列出目标数据库且JDBC驱动程序不支持Auto所需的元数据，则使用通用数据库。 更多信息，请访问： http ： //www.eclipse.org/eclipselink/documentation/2.4/jpa/extensions/p_target_database.htm#sthash.y1lrDjUn.dpuf ）