AccessControlException while connecting MySQL using JDBC in GWT hosted mode

Question

I want to connect to a mysql database at localhost:3306 using jdbc in a GWT servlet, but when I try connecting I get this error:

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

I know that I need to apply a security policy for tomcat to solve this problem, something like this:

grant codeBase "file:${catalina.home}/webapps/-" {
    permission java.net.SocketPermission "192.168.12.81:3306", "connect";
};

But I don't know where should I apply this change? Please provide a solution for both hosted & web mode.

Answer 1

Make sure you are not using the Google App Engine (I'm assuming here you are using the Google Eclipse Plugin): go to your project's properties -> Google -> App Engine, and make sure it's unchecked.

If this doesn't help, read through the suggestions in this thread.