【发布时间】：2012-04-21 01:38:50
【问题描述】：
我是 Google App Engine 的新手，我需要使用 GAE 制作应用程序。
我希望数据库是 MySQL。我在 Google Cloud SQL 中注册了有限的预览版，但我想同时在本地（离线）工作。即使我还没有访问 Google Cloud SQL 的权限，这可能吗？如果是这样，您能否向我提供 JDBC 脚本来实现这一点？以及任何需要的库。
我通常用这个连接到本地数据库：
package acc;
import java.sql.*;
import com.google.appengine.api.rdbms.AppEngineDriver;
import java.io.IOException;
import java.sql.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* provide database connection
*/
public class dbConnection {
static Connection conn;
static String url;
public static Connection getConnection()
{
try
{
String url = "jdbc:mysql://localhost:3306/gp";
Class.forName ("com.mysql.jdbc.Driver").newInstance ();
try
{
String userName = "root";
String password = "";
conn = DriverManager.getConnection (url, userName, password);
System.out.println ("Database connection established");
}
catch (Exception e)
{
System.err.println ("Cannot connect to database server");
}
}
catch(ClassNotFoundException e)
{
System.out.println(e);
} catch (InstantiationException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IllegalAccessException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return conn;
}
}
非常感谢
com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Could not create connection to database server.
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:525)
at com.google.appengine.tools.development.agent.runtime.Runtime.newInstance_(Runtime.java:126)
at com.google.appengine.tools.development.agent.runtime.Runtime.newInstance(Runtime.java:134)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
at com.mysql.jdbc.Util.getInstance(Util.java:386)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1013)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:987)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:982)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:927)
at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2464)
at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2207)
at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:797)
at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:525)
at com.google.appengine.tools.development.agent.runtime.Runtime.newInstance_(Runtime.java:126)
at com.google.appengine.tools.development.agent.runtime.Runtime.newInstance(Runtime.java:134)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:389)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:305)
at java.sql.DriverManager.getConnection(DriverManager.java:579)
at java.sql.DriverManager.getConnection(DriverManager.java:221)
at acc.dbConnection.getConnection(dbConnection.java:35)
at acc.DAO.getEmpList(DAO.java:40)
at acc.SelectEmpServlet.doGet(SelectEmpServlet.java:27)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
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:122)
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:78)
at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
at com.google.appengine.tools.development.JettyContainerService$ApiProxyHandler.handle(JettyContainerService.java:369)
at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
at org.mortbay.jetty.Server.handle(Server.java:326)
at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:923)
at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:547)
at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:212)
at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:409)
at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582)
Caused by: java.security.AccessControlException: access denied ("java.net.SocketPermission" "localhost" "resolve")
at java.security.AccessControlContext.checkPermission(AccessControlContext.java:366)
at java.security.AccessController.checkPermission(AccessController.java:555)
at java.lang.SecurityManager.checkPermission(SecurityManager.java:549)
at com.google.appengine.tools.development.DevAppServerFactory$CustomSecurityManager.checkPermission(DevAppServerFactory.java:252)
at java.lang.SecurityManager.checkConnect(SecurityManager.java:1048)
at java.net.InetAddress.getAllByName0(InetAddress.java:1203)
at java.net.InetAddress.getAllByName(InetAddress.java:1127)
at java.net.InetAddress.getAllByName(InetAddress.java:1063)
at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:247)
at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:298)
at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2385)
at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2422)
... 48 more
java.lang.NullPointerException
【问题讨论】：
-
你现在有什么问题？
-
以下错误和没有连接到本地数据库 "java.lang.ClassNotFoundException: com.mysql.jdbc.Driver An Exception has occurred!java.lang.NullPointerException"
-
mysql驱动jar在
WEB-INF/lib吗？ -
不，我现在添加这个 jar mysql-connector-java-5.1.19-bin 我现在有这个错误“发生异常！java.lang.NullPointerException”所以仍然无法工作
-
好的，必须有一个堆栈跟踪告诉你发生了什么......没有这些信息，任何人都无法帮助你。不过有一件奇怪的事情：你定义了
url两次。
标签： java mysql google-app-engine jdbc