嘿伙计们，我正在关注 GWT 开发人员指南，到目前为止一切正常，直到我尝试使用 AppEngine。我在 MacOS X 10.7.5 上安装了最新的 JDK 和 Eclipse。如果我尝试运行我的教程 StockExchange 程序，我会收到此错误：
objc[377]: Class JavaLaunchHelper is implemented in both /Library/Java/JavaVirtualMachines/jdk1.7.0_40.jdk/Contents/Home/bin/java and /Library/Java/JavaVirtualMachines/jdk1.7.0_40.jdk/Contents/Home/jre/lib/libinstrument.dylib. One of the two will be used. Which one is undefined.
Initializing App Engine server
Okt 07, 2013 10:24:00 PM com.google.apphosting.utils.config.AppEngineWebXmlReader readAppEngineWebXml
Information: Successfully processed /Users/HP/Desktop/StockWatcher/war/WEB-INF/appengine-web.xml
Okt 07, 2013 10:24:00 PM com.google.apphosting.utils.config.AppEngineWebXmlReader readAppEngineWebXml
Schwerwiegend: Received exception processing /Users/HP/Desktop/StockWatcher/war/WEB-INF/appengine-web.xml
com.google.apphosting.utils.config.AppEngineConfigException: appengine-web.xml does not contain a <threadsafe> element.
See http://code.google.com/appengine/docs/java/config/appconfig.html#Using_Concurrent_Requests for more information.
You probably want to enable concurrent requests.
at com.google.apphosting.utils.config.AppEngineWebXmlReader.readAppEngineWebXml(AppEngineWebXmlReader.java:85)
at com.google.apphosting.utils.config.EarHelper.readWebModule(EarHelper.java:166)
at com.google.appengine.tools.development.ApplicationConfigurationManager$WarModuleConfigurationHandle.readConfiguration(ApplicationConfigurationManager.java:399)
at com.google.appengine.tools.development.ApplicationConfigurationManager.<init>(ApplicationConfigurationManager.java:146)
at com.google.appengine.tools.development.ApplicationConfigurationManager.newWarConfigurationManager(ApplicationConfigurationManager.java:88)
at com.google.appengine.tools.development.DevAppServerImpl.<init>(DevAppServerImpl.java:139)
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:526)
at com.google.appengine.tools.development.DevAppServerFactory.doCreateDevAppServer(DevAppServerFactory.java:258)
at com.google.appengine.tools.development.DevAppServerFactory.access$000(DevAppServerFactory.java:36)
at com.google.appengine.tools.development.DevAppServerFactory$1.run(DevAppServerFactory.java:226)
at com.google.appengine.tools.development.DevAppServerFactory$1.run(DevAppServerFactory.java:224)
at java.security.AccessController.doPrivileged(Native Method)
at com.google.appengine.tools.development.DevAppServerFactory.createDevAppServer(DevAppServerFactory.java:224)
at com.google.appengine.tools.development.DevAppServerFactory.createDevAppServer(DevAppServerFactory.java:76)
at com.google.appengine.tools.development.DevAppServerFactory.createDevAppServer(DevAppServerFactory.java:60)
at com.google.appengine.tools.development.gwt.AppEngineLauncher.start(AppEngineLauncher.java:84)
at com.google.gwt.dev.DevMode.doStartUpServer(DevMode.java:509)
at com.google.gwt.dev.DevModeBase.startUp(DevModeBase.java:1093)
at com.google.gwt.dev.DevModeBase.run(DevModeBase.java:836)
at com.google.gwt.dev.DevMode.main(DevMode.java:311)
[ERROR] Unable to start App Engine server
com.google.apphosting.utils.config.AppEngineConfigException: Invalid configuration
at com.google.appengine.tools.development.DevAppServerImpl.reportDeferredConfigurationException(DevAppServerImpl.java:445)
at com.google.appengine.tools.development.DevAppServerImpl.doStart(DevAppServerImpl.java:225)
at com.google.appengine.tools.development.DevAppServerImpl.access$000(DevAppServerImpl.java:47)
at com.google.appengine.tools.development.DevAppServerImpl$1.run(DevAppServerImpl.java:212)
at com.google.appengine.tools.development.DevAppServerImpl$1.run(DevAppServerImpl.java:210)
at java.security.AccessController.doPrivileged(Native Method)
at com.google.appengine.tools.development.DevAppServerImpl.start(DevAppServerImpl.java:210)
at com.google.appengine.tools.development.gwt.AppEngineLauncher.start(AppEngineLauncher.java:97)
at com.google.gwt.dev.DevMode.doStartUpServer(DevMode.java:509)
at com.google.gwt.dev.DevModeBase.startUp(DevModeBase.java:1093)
at com.google.gwt.dev.DevModeBase.run(DevModeBase.java:836)
at com.google.gwt.dev.DevMode.main(DevMode.java:311)
Caused by: com.google.apphosting.utils.config.AppEngineConfigException: Invalid appengine-web.xml(/Users/HP/Desktop/StockWatcher/war/WEB-INF/appengine-web.xml) - appengine-web.xml does not contain a <threadsafe> element.
See http://code.google.com/appengine/docs/java/config/appconfig.html#Using_Concurrent_Requests for more information.
You probably want to enable concurrent requests.
at com.google.apphosting.utils.config.EarHelper.readWebModule(EarHelper.java:168)
at com.google.appengine.tools.development.ApplicationConfigurationManager$WarModuleConfigurationHandle.readConfiguration(ApplicationConfigurationManager.java:399)
at com.google.appengine.tools.development.ApplicationConfigurationManager.<init>(ApplicationConfigurationManager.java:146)
at com.google.appengine.tools.development.ApplicationConfigurationManager.newWarConfigurationManager(ApplicationConfigurationManager.java:88)
at com.google.appengine.tools.development.DevAppServerImpl.<init>(DevAppServerImpl.java:139)
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:526)
at com.google.appengine.tools.development.DevAppServerFactory.doCreateDevAppServer(DevAppServerFactory.java:258)
at com.google.appengine.tools.development.DevAppServerFactory.access$000(DevAppServerFactory.java:36)
at com.google.appengine.tools.development.DevAppServerFactory$1.run(DevAppServerFactory.java:226)
at com.google.appengine.tools.development.DevAppServerFactory$1.run(DevAppServerFactory.java:224)
at java.security.AccessController.doPrivileged(Native Method)
at com.google.appengine.tools.development.DevAppServerFactory.createDevAppServer(DevAppServerFactory.java:224)
at com.google.appengine.tools.development.DevAppServerFactory.createDevAppServer(DevAppServerFactory.java:76)
at com.google.appengine.tools.development.DevAppServerFactory.createDevAppServer(DevAppServerFactory.java:60)
at com.google.appengine.tools.development.gwt.AppEngineLauncher.start(AppEngineLauncher.java:84)
... 4 more
Unable to start embedded HTTP server
com.google.gwt.core.ext.UnableToCompleteException: (see previous log entries)
at com.google.appengine.tools.development.gwt.AppEngineLauncher.start(AppEngineLauncher.java:102)
at com.google.gwt.dev.DevMode.doStartUpServer(DevMode.java:509)
at com.google.gwt.dev.DevModeBase.startUp(DevModeBase.java:1093)
at com.google.gwt.dev.DevModeBase.run(DevModeBase.java:836)
at com.google.gwt.dev.DevMode.main(DevMode.java:311)
[ERROR] shell failed in doStartupServer method
我不知道如何解决这个问题。谢谢你的帮助。