我正在关注这个例子
。每当调用 find 时，我都会收到此错误：
java.lang.NullPointerException
at LoginAction.service(LoginAction.java:41)
at Dispatcher.doWork(Dispatcher.java:82)
at Dispatcher.doGet(Dispatcher.java:64)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:734)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:847)
at org.apache.catalina.core.ApplicationFilterChain.servletService(ApplicationFilterChain.java:427)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:315)
at org.apache.catalina.core.StandardContextValve.invokeInternal(StandardContextValve.java:287)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:218)
at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:648)
at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:593)
at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:94)
at com.sun.enterprise.web.PESessionLockingStandardPipeline.invoke(PESessionLockingStandardPipeline.java:98)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:222)
at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:648)
at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:593)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:587)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:1096)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:166)
at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:648)
at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:593)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:587)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:1096)
at org.apache.coyote.tomcat5.CoyoteAdapter.service(CoyoteAdapter.java:288)
at com.sun.enterprise.web.connector.grizzly.DefaultProcessorTask.invokeAdapter(DefaultProcessorTask.java:647)
at com.sun.enterprise.web.connector.grizzly.DefaultProcessorTask.doProcess(DefaultProcessorTask.java:579)
at com.sun.enterprise.web.connector.grizzly.DefaultProcessorTask.process(DefaultProcessorTask.java:831)
at com.sun.enterprise.web.connector.grizzly.DefaultReadTask.executeProcessorTask(DefaultReadTask.java:341)
at com.sun.enterprise.web.connector.grizzly.DefaultReadTask.doTask(DefaultReadTask.java:263)
at com.sun.enterprise.web.connector.grizzly.DefaultReadTask.doTask(DefaultReadTask.java:214)
at com.sun.enterprise.web.portunif.PortUnificationPipeline$PUTask.doTask(PortUnificationPipeline.java:380)
at com.sun.enterprise.web.connector.grizzly.TaskBase.run(TaskBase.java:265)
at com.sun.enterprise.web.connector.grizzly.ssl.SSLWorkerThread.run(SSLWorkerThread.java:106)
我不知道从哪里开始寻找。第 41 行是 operator.findOperator(1)，其中
@EJB
private OperatorBeanService operator;
我正在尝试在 Glassfish 2.1 上执行此操作。这就是坚持：
<persistence-unit name="persistMe" transaction-type="JTA">
<provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
<jta-data-source>jdbc/peciu</jta-data-source>
<properties>
<property name="eclipselink.jdbc.batch-writing" value="JDBC"/>
<property name="eclipselink.target-database" value="myDB"/>
<property name="eclipselink.target-server" value="host"/>
<property name="eclipselink.logging.level" value="ALL"/>
</properties>
</persistence-unit>
我用这种持久性尝试了一个单独的 JPA 项目：
<persistence-unit name="OperatorService" transaction-type="RESOURCE_LOCAL">
<provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
<class>Operator</class>
<properties>
<property name="eclipselink.jdbc.batch-writing" value="JDBC"/>
<property name="eclipselink.jdbc.driver" value="COM.ibm.db2os390.sqlj.jdbc.DB2SQLJDriver"/>
<property name="eclipselink.jdbc.url" value="jdbc:db2://host:50000/myDB"/>
<property name="eclipselink.jdbc.user" value="user"/>
<property name="eclipselink.jdbc.password" value="pass"/>
</properties>
</persistence-unit>
它工作得很好，从 OPERATOR 表返回结果。我不知道我错过了什么。感谢您的时间。尤利亚