Java/GWT/MySQL:连接被拒绝了？

我正在开发一个GWT Web应用程序,并尝试从我的RemoteServiceServlet实现(对于rpc)连接到mysql数据库.

服务器运行,我能够从我工作的机器连接到数据库.出于测试目的,我编写了一个只连接到数据库的小程序.这有效:

Class.forName("com.mysql.jdbc.Driver");
Connection connection = DriverManager.getConnection("jdbc:mysql://192.168.0.106:3306/dbname", "dbuser", "dbpasswd");

但是在我的gwt应用程序中,相同的行失败了大约100行堆栈跟踪,这是"原因":

Caused by: java.net.SocketException: java.security.AccessControlException: access denied (java.net.SocketPermission 192.168.0.106:3306 connect,resolve)
at com.mysql.jdbc.StandardSocketFactory.unwrapExceptionToProperClassAndThrowIt(StandardSocketFactory.java:408)
at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:269)
at com.mysql.jdbc.MysqlIO.(MysqlIO.java:294)
... 55 more

现在我的问题:为什么？

编辑:用于测试我使用chrome和gwt插件的开发模式

edit2:崩溃的代码部分:

public DataLinkImpl() {
Connection tmpConnection = null;
try {
  Class.forName("com.mysql.jdbc.Driver");
  tmpConnection = DriverManager.getConnection("jdbc:mysql://192.168.0.106:3306/dbname", "dbuser", "dbpasswd");
} catch (ClassNotFoundException e) {
  System.err.println("jdbc driver class not found");
} catch (SQLException e) {
  System.err.println("could not establish database connection");
  e.printStackTrace();
  e.getNextException().printStackTrace();
} finally {
  connection = tmpConnection;
}
}

使用以下堆栈跟踪:

could not establish database connection
com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at com.google.appengine.tools.development.agent.runtime.Runtime.newInstance_(Runtime.java:112)
at com.google.appengine.tools.development.agent.runtime.Runtime.newInstance(Runtime.java:120)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1116)
at com.mysql.jdbc.MysqlIO.(MysqlIO.java:344)
at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2333)
at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2370)
at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2154)
at com.mysql.jdbc.ConnectionImpl.(ConnectionImpl.java:792)
at com.mysql.jdbc.JDBC4Connection.(JDBC4Connection.java:47)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at com.google.appengine.tools.development.agent.runtime.Runtime.newInstance_(Runtime.java:112)
at com.google.appengine.tools.development.agent.runtime.Runtime.newInstance(Runtime.java:120)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:381)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:305)
at java.sql.DriverManager.getConnection(DriverManager.java:582)
at java.sql.DriverManager.getConnection(DriverManager.java:185)
at de.eikecochu.gwt.awidb.server.DataLinkImpl.(DataLinkImpl.java:23)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at java.lang.Class.newInstance0(Class.java:355)
at java.lang.Class.newInstance(Class.java:308)
at org.mortbay.jetty.servlet.Holder.newInstance(Holder.java:153)
at org.mortbay.jetty.servlet.ServletHolder.initServlet(ServletHolder.java:428)
at org.mortbay.jetty.servlet.ServletHolder.getServlet(ServletHolder.java:339)
at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:487)
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$ApiProxyHandler.handle(JettyContainerService.java:362)
at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
at org.mortbay.jetty.Server.handle(Server.java:326)
at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
at org.mortbay.jetty.HttpConnection$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.net.SocketException: java.security.AccessControlException: access denied (java.net.SocketPermission 192.168.0.106:3306 connect,resolve)
at com.mysql.jdbc.StandardSocketFactory.unwrapExceptionToProperClassAndThrowIt(StandardSocketFactory.java:408)
at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:269)
at com.mysql.jdbc.MysqlIO.(MysqlIO.java:294)
... 55 more
01.12.2011 02:33:09 com.google.appengine.tools.development.ApiProxyLocalImpl log
SCHWERWIEGEND: javax.servlet.ServletContext log: unavailable

java.lang.NullPointerException
at de.eikecochu.gwt.awidb.server.DataLinkImpl.(DataLinkImpl.java:29)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at java.lang.Class.newInstance0(Class.java:355)
at java.lang.Class.newInstance(Class.java:308)
at org.mortbay.jetty.servlet.Holder.newInstance(Holder.java:153)
at org.mortbay.jetty.servlet.ServletHolder.initServlet(ServletHolder.java:428)
at org.mortbay.jetty.servlet.ServletHolder.getServlet(ServletHolder.java:339)
at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:487)
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$ApiProxyHandler.handle(JettyContainerService.java:362)
at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
at org.mortbay.jetty.Server.handle(Server.java:326)
at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
at org.mortbay.jetty.HttpConnection$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)

01.12.2011 02:33:09 com.google.apphosting.utils.jetty.JettyLogger warn
WARNUNG: /awidb/datalink
java.lang.NullPointerException
at de.eikecochu.gwt.awidb.server.DataLinkImpl.(DataLinkImpl.java:29)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at java.lang.Class.newInstance0(Class.java:355)
at java.lang.Class.newInstance(Class.java:308)
at org.mortbay.jetty.servlet.Holder.newInstance(Holder.java:153)
at org.mortbay.jetty.servlet.ServletHolder.initServlet(ServletHolder.java:428)
at org.mortbay.jetty.servlet.ServletHolder.getServlet(ServletHolder.java:339)
at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:487)
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$ApiProxyHandler.handle(JettyContainerService.java:362)
at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
at org.mortbay.jetty.Server.handle(Server.java:326)
at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
at org.mortbay.jetty.HttpConnection$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)

edit3:我在/Library/Java/.../security/java.policy文件中添加了一个权限:

grant {
    permission java.net.SocketPermission "192.168.0.106:3306", "connect,resolve";
}

但仍然相同,我无法连接到数据库.我也尝试直接在db所在的机器上执行它,所以我在tomcat中部署了它(在那里添加了相同的权限),但仍然没有去.WTF？

edit4:为了证实这一点,我写了一个非常简单的网络应用程序:

EntryPoint类:

package de.eikecochu.gwt.gwttest.client;

import com.google.gwt.core.client.EntryPoint;
import com.google.gwt.core.client.GWT;
import com.google.gwt.event.dom.client.ClickEvent;
import com.google.gwt.event.dom.client.ClickHandler;
import com.google.gwt.user.client.rpc.AsyncCallback;
import com.google.gwt.user.client.ui.Button;
import com.google.gwt.user.client.ui.Label;
import com.google.gwt.user.client.ui.RootPanel;

public class GWTTest implements EntryPoint {
  private TestServiceAsync testservice = GWT.create(TestService.class);
  @Override
  public void onModuleLoad() {
    Button b = new Button("test");
    RootPanel.get("container").add(b);
    b.addClickHandler(new ClickHandler() {
      @Override
      public void onClick(ClickEvent event) {
        testservice.echo("test", new AsyncCallback() {
          @Override
          public void onFailure(Throwable caught) {
            RootPanel.get("container").add(new Label("error"));
          }
          @Override
          public void onSuccess(String result) {
            RootPanel.get("container").add(new Label(result));
          }
        });
      }
    });
  }
}

远程服务接口:

package de.eikecochu.gwt.gwttest.client;

import com.google.gwt.user.client.rpc.RemoteService;
import com.google.gwt.user.client.rpc.RemoteServiceRelativePath;

@RemoteServiceRelativePath("testservice")
public interface TestService extends RemoteService {

  String echo(String s);

}

远程服务异步接口:

package de.eikecochu.gwt.gwttest.client;

import com.google.gwt.user.client.rpc.AsyncCallback;

public interface TestServiceAsync {

  void echo(String s, AsyncCallback callback);

}

RemoteServiceServlet实现:

package de.eikecochu.gwt.gwttest.server;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

import com.google.gwt.user.server.rpc.RemoteServiceServlet;

import de.eikecochu.gwt.gwttest.client.TestService;

public class TestServiceImpl extends RemoteServiceServlet implements
    TestService {
  private static final long serialVersionUID = 1L;

  private final Connection connect() {
    String driver = "com.mysql.jdbc.Driver";
    String dblink = "jdbc:mysql://192.168.0.106:3306/";
    String dbname = "dbname";
    String dbuser = "dbuser";
    String dbpass = "dbpass";
    try {
      Class.forName(driver).newInstance();
    } catch (InstantiationException e) {
      e.printStackTrace();
    } catch (IllegalAccessException e) {
      e.printStackTrace();
    } catch (ClassNotFoundException e) {
      e.printStackTrace();
    }
    Connection conn = null;
    try {
      conn = DriverManager.getConnection(dblink + dbname, dbuser, dbpass);
    } catch (SQLException e) {
      System.err.println("mysql connection error: ");
      e.printStackTrace();
    }
    return conn;
  }

  @Override
  public String echo(String s) {
    Connection c = connect();
    return s;
  }

}

这也行不通.不在我的机器上,而不在localhost(db所在的位置)上.再次出现相同的错误(AccessControlException bla bla).

edit5: I tried to execute my app directly on my server, which means: i installed eclipse and gwt tools on the server and executed it there locally in chrome/development mode. Still the same error. I get the feeling that either my mysql/ubuntu have wrong configs or I am doing something wrong, fundamentally. Normally, it should be quite easy to connect to a database, yes? I mean, what is a website without a database...

edit6: as baba suggested, I tried to set System.setSecurityManager(null);

in my RemoteServlet right before connecting to the database. It throws following error (abbreviated):

java.security.AccessControlException: access denied (java.lang.RuntimePermission setSecurityManager)
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:252)
at java.lang.System.setSecurityManager0(System.java:273)
at java.lang.System.setSecurityManager(System.java:264)

so it seems I have a SecurityManager installed.

Also, I have tried to access my database with telnet. At first, my connection was refused but I changed my mysql-bind address to the ip of my server (192.168.0.106) and followed the steps here: http://ubuntu-commands.blogspot.com/2008/11/how-do-i-enable-remote-access-to-mysql.html

And when I telnet 192.168.0.106 3306 now, weird symbols appear:

eikes-macbook-air:~ eike$ telnet 192.168.0.106 3306
Trying 192.168.0.106...
Connected to eike-server.speedport.ip.
Escape character is '^]'.
=
5.1.58-1ubuntu1(b5|529h~!dYpI\rHP:qKc

ot packets out of orderConnection closed by foreign host.

It seems this is an error?

Plus, I searched for the AccessDenied error and found this link: http://code.google.com/p/gwt-examples/wiki/project_MySQLConn#Tomcat_Setup_Notes which describes exactly the error I am experiencing, although I use the Devmode for developing. Although following these steps didn't help (I edited my default /Library/.../security/java.policy file)

edit7: I installed postgresql and set up a very simple database just to test the connection. Without GWT it works fine, GWT produces the same error again. Therefore, it is not the fault of my mysql config. I played a bit with the java policy file, no reaction. GWT hates me :<

edit8: I tried both postgresql and mysql on another machine (this time win7) and executed my gwt app there locally (before & after editing the policy file), still the same error. This is unmistakably GWTs fault! It seems like the gwt devmode is not allowed to do anyting, anywhere...

Another question: the error clearly states "java.security.AccessControlException: access denied (java.net.SocketPermission localhost resolve)", so why does this still appear when I modify my java policy file to connect,resolve on the needed ports? It seems like that had absolutely no effect! I even tried grant AllPermission, no effect either.

Next, I found the "gwt-log.txt", which lists an error in the loading process:

Public resources found in...
[WARN] Error processing classpath URL 'file:/C:/Program Files (x86)/eclipse/plugin/com.google.gdt.eclipse.designer.hosted.2_2_2.4.2.r37x201110201837/gwt-dev-designtime.jar'
java.net.URISyntaxException: Illegal character in path at index 16: file:/C:/Program Files (x86)/eclipse/plugins/com.google.gdt.eclipse.designer.hosted.2_2_2.4.2.r37x201110201837/gwt-dev-designtime.jar
at java.net.URI$Parser.fail(Unknown Source)

I don't know what that is or if it's important, but it's not my fault!

您已使用 Google App Engine 安装了Google Eclipse插件.创建一个新的GWT项目并确保取消选择Google App Engine,然后重试.或者,从eclipse类路径中删除所有与GAE相关的jar文件.

GAE是Google提供的托管环境.它的环境非常有限.它不允许您打开套接字连接或读/写文件.数据库驱动程序打开套接字连接,因此GAE会阻止它出现安全性异常.

GWT和GAE是谷歌的两个独立产品,但Eclipse插件是相同的.不幸的是,它假设您希望将两种产品用作项目的一部分.