Java mysql GWT

[xxJohnnyxx]

Hello, I want to connect to a mysql server from the server side of my GWT code, like this:

@SuppressWarnings("serial")

public class CommunicationServiceImpl extends RemoteServiceServlet implements

CommunicationService 

{

@Override

public UserLogin communicationServer(UserLogin user) 

{

String hash =  BCrypt.hashpw(user.password, BCrypt.gensalt());

user.password = hash;

query();

return user;

}

public void query()

{

String username = "root";

String password = "root";

String driver = "com.mysql.jdbc.Driver";

String url = "jdbc:mysql://localhost:8889/User";

Connection conn = null;

try

{

Class.forName(driver);

conn = DriverManager.getConnection(url,username,password);

System.out.println("FOUND DRIVER");

}

catch(Exception e)

{

e.printStackTrace();

System.out.println("ERROR CONNECTING USER");

}

try

{

Statement stmt = conn.createStatement();

String sql = "SELECT Username FROM UserInformation";

ResultSet result = stmt.executeQuery(sql);

System.out.println("TRY TO EXECUTE QUERY");

while(result.next())

{

System.out.println(result.getString("Username"));

}

}

catch(Exception e)

{

e.printStackTrace();

}

}

}

But when I run the code, I get this error:

SCHWERWIEGEND: javax.servlet.ServletContext log: Exception while dispatching incoming RPC call

com.google.gwt.user.server.rpc.UnexpectedException: Service method 'public abstract de.mapJobs.jltech.shared.UserLogin de.mapJobs.jltech.client.CommunicationService.communicationServer(de.mapJobs.jltech.shared.UserLogin)' 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:60)

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:370)

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(Class.java:169)

at de.mapJobs.jltech.server.CommunicationServiceImpl.query(CommunicationServiceImpl.java:40)

at de.mapJobs.jltech.server.CommunicationServiceImpl.communicationServer(CommunicationServiceImpl.java:24)

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)

at java.lang.reflect.Method.invoke(Method.java:597)

at com.google.appengine.tools.development.agent.runtime.Runtime.invoke(Runtime.java:115)

at com.google.gwt.user.server.rpc.RPC.invokeAndEncodeResponse(RPC.java:569)

... 34 more

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

at java.security.AccessControlContext.checkPermission(AccessControlContext.java:374)

at java.security.AccessController.checkPermission(AccessController.java:546)

at java.lang.SecurityManager.checkPermission(SecurityManager.java:532)

at com.google.appengine.tools.development.DevAppServerFactory$CustomSecurityManager.checkPermission(DevAppServerFactory.java:283)

at com.google.appengine.tools.development.DevAppServerFactory$CustomSecurityManager.checkAccess(DevAppServerFactory.java:308)

at java.lang.ThreadGroup.checkAccess(ThreadGroup.java:299)

at java.lang.Thread.init(Thread.java:336)

at java.lang.Thread.<init>(Thread.java:472)

at com.mysql.jdbc.NonRegisteringDriver$1.<init>(NonRegisteringDriver.java:90)

at com.mysql.jdbc.NonRegisteringDriver.<clinit>(NonRegisteringDriver.java:89)

... 44 more

 

Any solutions for this problem? 

[Joseph Lust]

This is a database connection issue, not a GWT issue. However, if you try to make a connection to a database, triggered by an RPC call, the stack trace will start out with the RPC call. Check your database parameters you're sending and the settings on your database server as a good first place to look.

Sincerely,

Joseph

[Paul Robinson]

On 10/08/12 21:46, xxJohnnyxx wrote:

Hello, I want to connect to a mysql server from the server side of my GWT code, like this:

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

at java.security.AccessControlContext.checkPermission(AccessControlContext.java:374)

at java.security.AccessController.checkPermission(AccessController.java:546)

at java.lang.SecurityManager.checkPermission(SecurityManager.java:532)

at com.google.appengine.tools.development.DevAppServerFactory$CustomSecurityManager.checkPermission(DevAppServerFactory.java:283)

at com.google.appengine.tools.development.DevAppServerFactory$CustomSecurityManager.checkAccess(DevAppServerFactory.java:308)

You appear to have app engine support enabled, but app engine doesn't support connecting to a mysql database.

Paul