无法使用Google App Engine制作的应用程序运行

Question

I have been following this tutorial

to create a to-do list app using Google App Engine. When I go to deploy it I get this error

java.lang.ExceptionInInitializerError:

From looking at the output in the console it links to the following line in my code

EntityManager em = EMFService.get().createEntityManager();

I have seen something similar on this site but there was no solution to it. Below are the classes that are related to the error

Dao.Java

public enum Dao {
INSTANCE;

@SuppressWarnings("unchecked")
public List<Todo> listTodos() {

    EntityManager em = EMFService.get().createEntityManager();
    Query q = em.createQuery("select m from Todo m");
    List<Todo> todos = q.getResultList();
    return todos;
}

public void add(String userID, String summery, String description, String url) {

    synchronized(this) {

        EntityManager em = EMFService.get().createEntityManager();
        Todo todo = new Todo( userID, summery, description, url );
        em.persist(todo);
        em.close();

    }
}

@SuppressWarnings("unchecked")
public List<Todo> getTodo(String userID) {

    EntityManager em = EMFService.get().createEntityManager(); // Error links to here
    Query q = em.createQuery("select t from Todo t where t.author = :userID");
    q.setParameter("userID", userID);
    List<Todo> todos = q.getResultList();

    return todos;
}

public void remove(long id) {

    EntityManager em = EMFService.get().createEntityManager();

    try {
        Todo todo = em.find(Todo.class, id);
        em.remove(todo);
    } finally {
        em.close();
    }
}
}

EMFService.java

public class EMFService {

private static final EntityManagerFactory emfInstance = Persistence.createEntityManagerFactory("transactions-optional");

private EMFService() {}

public static EntityManagerFactory get() {
    return emfInstance;
}
}

Any help is greatly appreciated.

Console output

WARNING: Nested in javax.servlet.ServletException: java.lang.NoClassDefFoundError:        Could not initialize class com.chrismcnulty.gaetutorial.EMFService:
java.lang.NoClassDefFoundError: Could not initialize class      com.chrismcnulty.gaetutorial.EMFService
at com.chrismcnulty.gaetutorial.Dao.getTodo(Dao.java:35)
at org.apache.jsp.TodoApplication_jsp._jspService(TodoApplication_jsp.java:92)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:377)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
at com.google.appengine.tools.development.PrivilegedJspServlet.access$101(PrivilegedJspServlet.java:23)
at com.google.appengine.tools.development.PrivilegedJspServlet$2.run(PrivilegedJspServlet.java:61)
at java.security.AccessController.doPrivileged(Native Method)
at com.google.appengine.tools.development.PrivilegedJspServlet.service(PrivilegedJspServlet.java:58)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)
at com.google.appengine.api.socket.dev.DevSocketFilter.doFilter(DevSocketFilter.java:74)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.appengine.tools.development.ResponseRewriterFilter.doFilter(ResponseRewriterFilter.java:123)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.appengine.tools.development.HeaderVerificationFilter.doFilter(HeaderVerificationFilter.java:34)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.appengine.api.blobstore.dev.ServeBlobFilter.doFilter(ServeBlobFilter.java:61)
at org.mortbay.jetty.servlet.ServletHandler$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.DevAppServerServersFilter.doFilter(DevAppServerServersFilter.java:106)
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:421)
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$RequestHandler.headerComplete(HttpConnection.java:923)
at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:547)
at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:212)
at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:409)
at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582)

Answer 1

This is likely actually cased by it not being able to initialize the EMFService class. static members are initialized when the class is loaded. The line that's actually failing is this:

private static final EntityManagerFactory emfInstance = Persistence.createEntityManagerFactory("transactions-optional");

Is "transactions-optional" maybe wrong?