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javaservletsjpapersistence

(persistence) Entity Manager can not be created

I am having this problem and its 2 days I can not figure out why is happening. I want to verify login. My code:

public String Verify(String name, String password) {
String admin="";
    Query q = emf
            .createEntityManager()
            .createQuery(
                    "SELECT u FROM user u where u.name = :name and u.password=:password");
    q.setParameter("name", name);
    q.setParameter("password", password);
    User u = (User) q.getSingleResult();

    if (u.getAdmin().equalsIgnoreCase("yes")) {
        admin = "yes";
    } else {
        admin = "no";
    }

    return admin;
}

I am getting this error then:

java.lang.NullPointerException
at db.DbProcessor.Verify(DbProcessor.java:19)
at controller.VerifikoServlet.doGet(VerifikoServlet.java:25)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:225)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:169)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:927)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:999)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:565)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:309)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
at java.lang.Thread.run(Thread.java:722)

Line 19 is ".createEntityManager()"

Solution

  • I fixed the problem writing this for initializing the Entity Factory Manager:

    private static EntityManagerFactory factory = Persistence
        .createEntityManagerFactory("PROJECT_NAME");
EntityManager em = factory.createEntityManager();