无法创建与G​​oogle Cloud SQL数据库的连接

Question

我无法将我的数据库连接从我的应用引擎实例连接到我的云sql数据库。无论出于何种原因，此代码最近才停止工作。在调用DriverManager.getConnection(url, user, password);之后，此代码基本上不会返回任何内容，并导致包含堆栈跟踪。

问题代码：

public static Connection createConnection(){
        String url = null;
        String user = ******;
        String password = ******;
        try {
            if (SystemProperty.environment.value() ==
                    SystemProperty.Environment.Value.Production) {
                Class.forName("com.mysql.jdbc.GoogleDriver");


url = "jdbc:google:mysql://{project_id}:{instance}/{db_name}";
            } else {
                Class.forName("com.mysql.jdbc.Driver");
                url = "jdbc:mysql://{my_ip}:3306/{db_name}";
            }
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
        try {
            Connection conn = DriverManager.getConnection(url, user, password);
            return conn;
        } catch (SQLException e) {
            e.printStackTrace();
            return null;
        }
    }

堆栈跟踪

com.google.api.server.spi.SystemService invokeServiceMethod: null
java.lang.NullPointerException
    at com.book.system.spi.BookForSaleV1.list(BookForSaleV1.java:77)
    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:45)
    at com.google.api.server.spi.SystemService.invokeServiceMethod(SystemService.java:359)
    at com.google.api.server.spi.SystemServiceServlet.execute(SystemServiceServlet.java:124)
    at com.google.api.server.spi.SystemServiceServlet.doPost(SystemServiceServlet.java:82)
    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$CachedChain.doFilter(ServletHandler.java:1166)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
    at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
    at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
    at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
    at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)
    at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
    at org.mortbay.jetty.Server.handle(Server.java:326)
    at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
    at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:923)
    at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
    at com.google.tracing.TraceContext$TraceContextRunnable.runInContext(TraceContext.java:437)
    at com.google.tracing.TraceContext$TraceContextRunnable$1.run(TraceContext.java:444)
    at com.google.tracing.CurrentContext.runInContext(CurrentContext.java:188)
    at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContextNoUnref(TraceContext.java:308)
    at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContext(TraceContext.java:300)
    at com.google.tracing.TraceContext$TraceContextRunnable.run(TraceContext.java:441)
    at java.lang.Thread.run(Thread.java:724)