Question

I’m slowly getting through my exceptions on my code using GWT + Hibernate, my server side class is as follows…

public class GreetingServiceImpl extends RemoteServiceServlet implements
    GreetingService {

public String greetServer(String input) throws IllegalArgumentException {
    // Verify that the input is valid. 
    if (!FieldVerifier.isValidName(input)) {
        // If the input is not valid, throw an IllegalArgumentException back to
        // the client.
        throw new IllegalArgumentException(
                "Name must be at least 4 characters long");
    }

    // Escape data from the client to avoid cross-site script vulnerabilities.
    input = escapeHtml(input);
    User user = new User();
    user.setFirstName(input);
    DaoFactory factory = new DaoFactory();
    try {
        factory.create(user);
    } catch (Exception e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    return "User : " + input + " added";
}

/**
 * Escape an html string. Escaping data received from the client helps to
 * prevent cross-site script vulnerabilities.
 * 
 * @param html the html string to escape
 * @return the escaped string
 */
private String escapeHtml(String html) {
    if (html == null) {
        return null;
    }
    return html.replaceAll("&", "&amp;").replaceAll("<", "&lt;")
            .replaceAll(">", "&gt;");
}

This receives a string, sets the users firstname as this string and commits it to the db but I get the following error…

[ERROR] javax.servlet.ServletContext log: Exception while dispatching incoming RPC call
com.google.gwt.user.server.rpc.UnexpectedException: Service method 'public abstract java.lang.String com.behaviour.app.client.GreetingService.greetServer(java.lang.String) throws java.lang.IllegalArgumentException' threw an unexpected exception: java.lang.ExceptionInInitializerError
    at com.google.gwt.user.server.rpc.RPC.encodeResponseForFailure(RPC.java:385)
    at com.google.gwt.user.server.rpc.RPC.invokeAndEncodeResponse(RPC.java:588)
    at com.google.gwt.user.server.rpc.RemoteServiceServlet.processCall(RemoteServiceServlet.java:208)
    at com.google.gwt.user.server.rpc.RemoteServiceServlet.processPost(RemoteServiceServlet.java:248)
    at com.google.gwt.user.server.rpc.AbstractRemoteServiceServlet.doPost(AbstractRemoteServiceServlet.java:62)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
    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$CachedChain.doFilter(ServletHandler.java:1166)
    at com.google.appengine.tools.development.HeaderVerificationFilter.doFilter(HeaderVerificationFilter.java:35)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.appengine.api.blobstore.dev.ServeBlobFilter.doFilter(ServeBlobFilter.java:58)
    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:122)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.appengine.tools.development.BackendServersFilter.doFilter(BackendServersFilter.java:97)
    at org.mortbay.jetty.servlet.ServletHandler$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.apphosting.utils.jetty.DevAppEngineWebAppContext.handle(DevAppEngineWebAppContext.java:70)
    at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
    at com.google.appengine.tools.development.JettyContainerService$ApiProxyHandler.handle(JettyContainerService.java:351)
    at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
    at org.mortbay.jetty.Server.handle(Server.java:326)
    at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
    at org.mortbay.jetty.HttpConnection$RequestHandler.content(HttpConnection.java:938)
    at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:755)
    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)
Caused by: java.lang.ExceptionInInitializerError
    at com.behaviour.hibernate.HibernateUtil.<clinit>(HibernateUtil.java:21)
    at com.behaviour.hibernate.DaoFactory.create(DaoFactory.java:9)
    at com.behaviour.app.server.GreetingServiceImpl.greetServer(GreetingServiceImpl.java:32)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:616)
    at com.google.appengine.tools.development.agent.runtime.Runtime.invoke(Runtime.java:100)
    at com.google.gwt.user.server.rpc.RPC.invokeAndEncodeResponse(RPC.java:569)
    ... 34 more
Caused by: java.lang.ExceptionInInitializerError
    at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:266)
    at java.sql.DriverManager.getConnection(DriverManager.java:620)
    at java.sql.DriverManager.getConnection(DriverManager.java:169)
    at org.hibernate.connection.DriverManagerConnectionProvider.getConnection(DriverManagerConnectionProvider.java:133)
    at org.hibernate.cfg.SettingsFactory.buildSettings(SettingsFactory.java:113)
    at org.hibernate.cfg.Configuration.buildSettingsInternal(Configuration.java:2863)
    at org.hibernate.cfg.Configuration.buildSettings(Configuration.java:2859)
    at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1870)
    at com.behaviour.hibernate.HibernateUtil.<clinit>(HibernateUtil.java:15)
    ... 42 more
Caused by: java.security.AccessControlException: access denied (java.lang.RuntimePermission modifyThreadGroup)
    at java.security.AccessControlContext.checkPermission(AccessControlContext.java:393)
    at java.security.AccessController.checkPermission(AccessController.java:553)
    at java.lang.SecurityManager.checkPermission(SecurityManager.java:549)
    at com.google.appengine.tools.development.DevAppServerFactory$CustomSecurityManager.checkPermission(DevAppServerFactory.java:166)
    at com.google.appengine.tools.development.DevAppServerFactory$CustomSecurityManager.checkAccess(DevAppServerFactory.java:191)
    at java.lang.ThreadGroup.checkAccess(ThreadGroup.java:315)
    at java.lang.Thread.init(Thread.java:353)
    at java.lang.Thread.<init>(Thread.java:437)
    at java.util.TimerThread.<init>(Timer.java:478)
    at java.util.Timer.<init>(Timer.java:100)
    at java.util.Timer.<init>(Timer.java:146)
    at com.mysql.jdbc.Connection.<clinit>(Connection.java:201)
    ... 51 more

I’m not sure really how to approach this. The classes involved are as follows…

public class HibernateUtil 
{
  private static final SessionFactory sessionFactory;

   static 
   {
    try 
      {
       // Create the SessionFactory from hibernate.cfg.xml
       sessionFactory = new Configuration().configure().buildSessionFactory();
       } 
       catch (Throwable ex)
       {
         // Make sure you log the exception, as it might be swallowed
         System.err.println("Initial SessionFactory creation failed." + ex);
         throw new ExceptionInInitializerError(ex);
       }
    }

    public static SessionFactory getSessionFactory()
    {
     return sessionFactory;
    }
 }

and

public class DaoFactory
{
   public void create(Object obj)throws Exception
   {
     Session session = HibernateUtil.getSessionFactory().getCurrentSession();
     session.beginTransaction();
     session.save(obj);
     session.getTransaction().commit();
   }
}

Thanks,

Apologies for not really explaining but I’m new to GWT and Hibernate.

Answer 1

You seem to be running your application in Google App Engine’s development server.

If your server application is a Google App Engine application, it may not use Hibernate. The only way to persist data in a GAE application is to use the App Engine DataStore. The App Engine development server has a security manager that replicates what is done on the actual Google App Engine server, and which forbids the MySQL driver to create and modify thread groups, as the stack trace indicates.

If your server application is a traditional web application intended to be deployed in a standard Java EE appserver (Tomcat, Jetty, GlassFish, etc.), then make it a web application and deploy it in one of those servers.