MYSQL driver error in GWT

Question

I have been trying to connect my GWT-project to my MySQL database for several hours but im stuck getting a strange error over and over again when loading the drivers.

The code for the server is: Note that im just trying to load the drivers for mysql and that im using the sample project that comes with GWT. The saveToDB(String) is the interesting part.

package test.server;



import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;

import test.client.GreetingService;
import com.google.gwt.user.server.rpc.RemoteServiceServlet;

/**
 * The server side implementation of the RPC service.
 */
@SuppressWarnings("serial")
public class GreetingServiceImpl extends RemoteServiceServlet implements
        GreetingService {

    public String greetServer(String input){
        // Verify that the input is valid. 
        saveToDB(input);
        String serverInfo = getServletContext().getServerInfo();
        String userAgent = getThreadLocalRequest().getHeader("User-Agent");

        // Escape data from the client to avoid cross-site script vulnerabilities.
        input = escapeHtml(input);
        userAgent = escapeHtml(userAgent);


        return "Hello, " + input + "!<br><br>I am running " + serverInfo
                + ".<br><br>It looks like you are using:<br>" + userAgent;
    }

    /**
     * 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;");
    }

    public void saveToDB(String input){
        String query = "INSERT INTO `oryx.model`" +
                "VALUES ('" + input + "');";
                // Save the model that is in variable "message" (very long string/text)
                //try {

                Connection conn = getConn();
               // Statement update = (Statement) conn.createStatement();
                //update.executeUpdate(query);

                //get last id 
               /*ResultSet result = (ResultSet) update.getGeneratedKeys(); 
                if (result != null && result.next()) { 
                    int rsId = result.getInt(1);  
                }

                result.close();
                update.close();
                conn.close();
            } catch(SQLException e) {
                System.err.println("Mysql Statement Error: " + query);
                e.printStackTrace();
            }*/

    }
    private Connection getConn() {

        Connection conn     = null;
        String url          = "jdbc:mysql://localhost:3306/";
        String db           = "mysqld";
        String driver       = "com.mysql.jdbc.Driver";
        String user         = "user";
        String pass         = "pass";



        try {
            System.out.println("ERROR 1");
            Class.forName("com.mysql.jdbc.Driver").newInstance();
            System.out.println("ERROR 2");
        } catch (Exception e) {
            // TODO Auto-generated catch block
            //e.printStackTrace();
            System.out.println("ERROR 3");
        } 
        //conn = DriverManager.getConnection(url+db, user, pass);

        //SQL EXCEPTION
        //System.err.println("Mysql Connection Error: ");
        //CLASS NOT FOUND
      //e.printStackTrace();
            return conn;
}
}

The error i always get:

SEVERE: javax.servlet.ServletContext log: Exception while dispatching incoming RPC call com.google.gwt.user.server.rpc.UnexpectedException: Service method 'public abstract java.lang.String test.client.GreetingService.greetServer(java.lang.String)' threw an unexpected exception: java.lang.ExceptionInInitializerError at com.google.gwt.user.server.rpc.RPC.encodeResponseForFailure(RPC.java:389) at com.google.gwt.user.server.rpc.RPC.invokeAndEncodeResponse(RPC.java:579) 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$CachedChain.doFilter(ServletHandler.java:1166) at com.google.appengine.api.socket.dev.DevSocketFilter.doFilter(DevSocketFilter.java:74) at org.mortbay.jetty.servlet.ServletHandler$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$CachedChain.doFilter(ServletHandler.java:1157) at com.google.appengine.tools.development.BackendServersFilter.doFilter(BackendServersFilter.java:97) at org.mortbay.jetty.servlet.ServletHandler$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.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$ApiProxyHandler.handle(JettyContainerService.java:409) at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152) at org.mortbay.jetty.Server.handle(Server.java:326) at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542) at org.mortbay.jetty.HttpConnection$RequestHandler.content(HttpConnection.java:938) at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:755) at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:218) at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404) at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:409) at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582) Caused by: java.lang.ExceptionInInitializerError at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Unknown Source) at test.server.GreetingServiceImpl.getConn(GreetingServiceImpl.java:88) at test.server.GreetingServiceImpl.saveToDB(GreetingServiceImpl.java:56) at test.server.GreetingServiceImpl.greetServer(GreetingServiceImpl.java:22) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at com.google.appengine.tools.development.agent.runtime.Runtime.invoke(Runtime.java:115) at com.google.gwt.user.server.rpc.RPC.invokeAndEncodeResponse(RPC.java:561) ... 38 more Caused by: java.security.AccessControlException: access denied (java.lang.RuntimePermission modifyThreadGroup) at java.security.AccessControlContext.checkPermission(Unknown Source) at java.security.AccessController.checkPermission(Unknown Source) at java.lang.SecurityManager.checkPermission(Unknown Source) at com.google.appengine.tools.development.DevAppServerFactory$CustomSecurityManager.checkPermission(DevAppServerFactory.java:289) at com.google.appengine.tools.development.DevAppServerFactory$CustomSecurityManager.checkAccess(DevAppServerFactory.java:314) at java.lang.ThreadGroup.checkAccess(Unknown Source) at java.lang.Thread.init(Unknown Source) at java.lang.Thread.(Unknown Source) at com.mysql.jdbc.NonRegisteringDriver$1.(NonRegisteringDriver.java:90) at com.mysql.jdbc.NonRegisteringDriver.(NonRegisteringDriver.java:89) ... 49 more

If you want you can have a look on the whole code at the following url: http://www19.zippyshare.com/v/9248211/file.html

All help would be very much appreciated.

//Sami

Answer 1

Caused by: java.security.AccessControlException: access denied (java.lang.RuntimePermission modifyThreadGroup)

and

at com.google.appengine.tools.development.DevAppServerFactory$CustomSecurityManager

are the interesting parts.

You cannot use MySQL on AppEngine: https://developers.google.com/appengine/docs/java/jrewhitelist

Unless you use CloudSQL, for it has a specific API: https://developers.google.com/appengine/docs/java/cloud-sql/developers-guide