I always get a NullPointerException with this: public class Servlet1 extends javax.servlet.http.HttpServlet implements javax.servlet.Servlet { | | @PersistenceUnit(name="EJBProject1") | EntityManagerFactory emf; | | protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { | response.setContentType("text/html"); | response.setHeader("Pragma", "No-cache"); | response.setDateHeader("Expires", 0); | response.setHeader("Cache-Control", "no-cache"); | | EntityManager em1 = emf.createEntityManager(); | Query query1 = em1.createQuery("select b from benutzer b"); | List users = query1.getResultList(); | PrintWriter writer = response.getWriter(); | | for (Iterator iterator = users.iterator(); iterator.hasNext();) { | Benutzer benutzer = (Benutzer) iterator.next(); | writer.print(benutzer.getName()); | } | writer.flush(); | } | } I failed to figure out whats going wrong for hours, had my problems with some other issues too. But unlike those, I did not manage to fix this one. The exception: 03:29:09,125 ERROR [[Servlet1]] Servlet.service() for servlet Servlet1 threw exception | java.lang.NullPointerException | at com.Servlet1.doGet(Servlet1.java:46) | at javax.servlet.http.HttpServlet.service(HttpServlet.java:690) | at javax.servlet.http.HttpServlet.service(HttpServlet.java:803) | at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) | at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) | at org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96) | at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) | at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) | at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:230) | at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175) | at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:179) | at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:84) | at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128) | at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:104) | at org.jboss.web.tomcat.service.jca.CachedConnectionValve.invoke(CachedConnectionValve.java:156) | at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) | at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:241) | at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844) | at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:580) | at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447) | at java.lang.Thread.run(Unknown Source) | I use JBoss 4.2.0 and Eclipse 3.3M6 with M6 WTP. Here is the persistence.xml: <?xml version="1.0" encoding="UTF-8"?> | <persistence version="1.0" 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"> | <persistence-unit name="EJBProject1"> | <provider>org.hibernate.ejb.HibernatePersistence</provider> | <jta-data-source>java:TestDS</jta-data-source> | <class>com.Benutzer</class> | <properties> | <property name="hibernate.dialect" | value="org.hibernate.dialect.MySQLDialect" /> | <property name="hibernate.transaction.manager_lookup_class" | value="org.hibernate.transaction.JBossTransactionManagerLookup"/> | | </properties> | </persistence-unit> | </persistence> | The Datastore-Definition (I put the driver in place and it gets loaded successfully according to the logs) <local-tx-datasource> | <jndi-name>TestDS</jndi-name> | <connection-url>jdbc:mysql://...:3306/test</connection-url> | <driver-class>com.mysql.jdbc.Driver</driver-class> | <user-name>...</user-name> | <password>...</password> | <min-pool-size>5</min-pool-size> | <max-pool-size>20</max-pool-size> | | <metadata> | <type-mapping>mySQL</type-mapping> | </metadata> | </local-tx-datasource> By the way, I came across this problem while following this tutorial: http://www.eclipse.org/webtools/jst/components/j2ee/scenarios/jee5_applic... I want to do what is done there, with JBoss, Hibernate and a MySQL Server Here you can find my project files: http://hellekalek.com/diverses/workspace.zip I really hope somebody can tell me what I am doing wrong. I lost all hope. Its just such a small tutorial that I want to follow, it can't be that difficult ... I thought. (of course its a little different because they don't use JBoss, but its really not a big project) View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4046344#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...