基本上是通过eclipsejavaweb项目连接到我的云sql数据库
检查表
1） 将我的google app engine sdk更新至最新的1.9.34版本
2） 将我的jdbc com.mysql.jdbc.driver更新到最新的5.1.38版本
3） 将jdbc驱动程序添加到构建路径
我根本无法连接到google cloud sql，因此出现以下错误：

java.security.AccessControlException: access denied ("java.lang.RuntimePermission" "modifyThreadGroup")
    at java.security.AccessControlContext.checkPermission(AccessControlContext.java:372)
    at java.security.AccessController.checkPermission(AccessController.java:559)
    at java.lang.SecurityManager.checkPermission(SecurityManager.java:549)
    at com.google.appengine.tools.development.DevAppServerFactory$CustomSecurityManager.checkPermission(DevAppServerFactory.java:429)
    at com.google.appengine.tools.development.DevAppServerFactory$CustomSecurityManager.checkAccess(DevAppServerFactory.java:454)
    at java.lang.ThreadGroup.checkAccess(ThreadGroup.java:315)
    at java.lang.Thread.init(Thread.java:391)
    at java.lang.Thread.init(Thread.java:349)
    at java.lang.Thread.<init>(Thread.java:445)
    at java.util.TimerThread.<init>(Timer.java:499)
    at java.util.Timer.<init>(Timer.java:101)
    at java.util.Timer.<init>(Timer.java:146)
    at com.mysql.jdbc.ConnectionImpl.<clinit>(ConnectionImpl.java:208)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:191)
    at com.google.appengine.tools.development.agent.runtime.RuntimeHelper.checkRestricted(RuntimeHelper.java:70)
    at com.google.appengine.tools.development.agent.runtime.Runtime.checkRestricted(Runtime.java:65)
    at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:283)
    at java.sql.DriverManager.getConnection(DriverManager.java:571)
    at java.sql.DriverManager.getConnection(DriverManager.java:233)
    at com.dinuka.myapp.servlets.PlanServlet.doPost(PlanServlet.java:59)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)

搜索了一整天，逐字逐句地浏览了stackoverflow上的所有相关问题。我要把头发拔出来了：d
下面是我连接数据库的简单代码。不敢相信我做错了什么：

public class MyServlet extends HttpServlet {

    @Override
    public void doPost(HttpServletRequest req, HttpServletResponse resp) throws IOException {

        String url = null;
        try {
            if (SystemProperty.environment.value() == SystemProperty.Environment.Value.Production) {
                // Load the class that provides the new "jdbc:google:mysql://" prefix.
                Class.forName("com.mysql.jdbc.GoogleDriver");
                url = "jdbc:google:mysql://app_id:instance_id/data?user=root";
            } else {
                // Local MySQL instance to use during development.
                Class.forName("com.mysql.jdbc.Driver");
                url = "jdbc:mysql://instance-ip:3306/data?user=root";
            }
        } catch (Exception e) {
            e.printStackTrace();
            return;
        }

        PrintWriter out = resp.getWriter();
        try {
            Connection conn = DriverManager.getConnection(url);
            System.out.println("Connection established");
            out.println("Connection established");
            try {
            } finally {
                conn.close();
            }
        } catch (SQLException e) {
            out.append(e.getMessage());
            e.printStackTrace();
        }
    }

}

请修复这个错误，谷歌团队！同时，有人能帮我渡过难关吗？