GWT 示例应用程序在 IntelliJ IDEA 中不起作用答案

【问题标题】：GWT Sample Application not working in IntelliJ IDEAGWT 示例应用程序在 IntelliJ IDEA 中不起作用
【发布时间】：2019-03-25 08:44:19
【问题描述】：

我一直在尝试开始使用 GWT，但是我不想从我的学生 IntelliJ IDEA Ultimate License 切换到 Eclipse，这是 gwtproject.org 教程中使用的 IDE。在本教程中，他们首先希望您使用 webAppCreator 创建一个示例 Web 应用程序，我认为它是在 IntelliJ 中打开具有 GWT 支持的新项目时可以创建的示例应用程序。然而，我的问题是，在启动他们的示例应用程序时，我在开发模式选项卡中收到大量错误消息。启动浏览器后，只有一条 HTTP 错误 503 消息，表示服务不可用。这是使用安装了 apache ant 的 2.8.2 版本的 gwt（如果相关的话）。使用 2.7.0 gwt 发行版我什至没有到达那里，因为它几乎立即崩溃。

感谢您的帮助！

我不确定这是否仍然准确，但我读到 IntelliJ 仅支持 gwt 2.7.0，这就是我在问题中包含两者的原因。

使用 Java 1.8 和 gwt 2.7.0 的开发模式日志

Runing CodeServer with parameters: [-noprecompile, -port, 9876, -sourceLevel, 1.7, -bindAddress, 127.0.0.1, -launcherDir, C:\Users\nicol\.IntelliJIdea2018.3\system\gwt\java18and270.a6677367\java18and270.73130fb9\run\www, -logLevel, INFO, com.mySampleApplication.MySampleApplication]
Mär 25, 2019 12:45:31 PM java.util.prefs.WindowsPreferences <init>
WARNING: Could not open/create prefs root node Software\JavaSoft\Prefs at root 0x80000002. Windows RegCreateKeyEx(...) returned error code 5.
Super Dev Mode starting up
   workDir: C:\Users\nicol\AppData\Local\Temp\gwt-codeserver-4172072951619368748.tmp
Loading modules
   com.mySampleApplication.MySampleApplication
      Validating <servlet> tags for module 'MySampleApplication'
      For additional info see: file:/G:/nicol/Libraries/OneDrive/JavaDevelopment/WebDev/gwt-2.7.0/doc/helpInfo/servletMappings.html
         [WARN] Module declares a servlet class 'com.mySampleApplication.server.MySampleApplicationServiceImpl', but the web.xml has no corresponding declaration; please add the following lines to your web.xml:
<servlet>
  <servlet-name>mySampleApplicationServiceImpl</servlet-name>
  <servlet-class>com.mySampleApplication.server.MySampleApplicationServiceImpl</servlet-class>
</servlet>
<servlet-mapping>
  <servlet-name>mySampleApplicationServiceImpl</servlet-name>
  <url-pattern>/MySampleApplication/MySampleApplicationService</url-pattern>
</servlet-mapping>
   Loading Java files in com.mySampleApplication.MySampleApplication.
Starting Jetty on port 8888
   [WARN] Failed startup of context c.g.g.d.s.j.WebAppContextWithReload{/,file:/C:/Users/nicol/.IntelliJIdea2018.3/system/gwt/java18and270.a6677367/java18and270.73130fb9/run/www/},C:\Users\nicol\.IntelliJIdea2018.3\system\gwt\java18and270.a6677367\java18and270.73130fb9\run\www
java.lang.NullPointerException
    at org.eclipse.jetty.servlet.ServletHolder.compareTo(ServletHolder.java:204)
    at java.util.ComparableTimSort.countRunAndMakeAscending(ComparableTimSort.java:321)
    at java.util.ComparableTimSort.sort(ComparableTimSort.java:188)
    at java.util.Arrays.sort(Arrays.java:1246)
    at org.eclipse.jetty.servlet.ServletHandler.initialize(ServletHandler.java:770)
    at org.eclipse.jetty.servlet.ServletContextHandler.startContext(ServletContextHandler.java:265)
    at org.eclipse.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1242)
    at org.eclipse.jetty.server.handler.ContextHandler.doStart(ContextHandler.java:717)
    at org.eclipse.jetty.webapp.WebAppContext.doStart(WebAppContext.java:494)
    at com.google.gwt.dev.shell.jetty.JettyLauncher$WebAppContextWithReload.doStart(JettyLauncher.java:541)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:64)
    at org.eclipse.jetty.server.handler.HandlerWrapper.doStart(HandlerWrapper.java:95)
    at org.eclipse.jetty.server.handler.RequestLogHandler.doStart(RequestLogHandler.java:162)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:64)
    at org.eclipse.jetty.server.handler.HandlerWrapper.doStart(HandlerWrapper.java:95)
    at org.eclipse.jetty.server.Server.doStart(Server.java:282)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:64)
    at com.google.gwt.dev.shell.jetty.JettyLauncher.start(JettyLauncher.java:740)
    at com.google.gwt.dev.DevMode.doStartUpServer(DevMode.java:632)
    at com.google.gwt.dev.DevModeBase.startUp(DevModeBase.java:1054)
    at com.google.gwt.dev.DevModeBase.run(DevModeBase.java:836)
    at com.google.gwt.dev.DevMode.main(DevMode.java:413)
   Module setup completed in 13378 ms

The code server is ready at http://127.0.0.1:9876/
Code server started in 13692 ms
waited 9583 ms for code server to finish
Dev Mode initialized. Startup URL: 
http://127.0.0.1:8888/MySampleApplication.html
[ERROR] 503 - GET /MySampleApplication.html (127.0.0.1) 1311 bytes
   Request headers
      Host: 127.0.0.1:8888
      User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:65.0) Gecko/20100101 Firefox/65.0
      Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
      Accept-Language: de,en-US;q=0.7,en;q=0.3
      Accept-Encoding: gzip, deflate
      DNT: 1
      Connection: keep-alive
      Upgrade-Insecure-Requests: 1
   Response headers
      Cache-Control: must-revalidate,no-cache,no-store
      Content-Type: text/html;charset=ISO-8859-1
      Content-Length: 1311
[ERROR] 503 - GET /favicon.ico (127.0.0.1) 1298 bytes
   Request headers
      Host: 127.0.0.1:8888
      User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:65.0) Gecko/20100101 Firefox/65.0
      Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
      Accept-Language: de,en-US;q=0.7,en;q=0.3
      Accept-Encoding: gzip, deflate
      DNT: 1
      Connection: keep-alive
   Response headers
      Cache-Control: must-revalidate,no-cache,no-store
      Content-Type: text/html;charset=ISO-8859-1
      Content-Length: 1298

使用 java 1.8 和 gwt 2.8.2 的开发模式日志

    Running CodeServer with parameters: [-noprecompile, -port, 9876, -sourceLevel, 1.8, -bindAddress, 127.0.0.1, -launcherDir, C:\Users\nicol\.IntelliJIdea2018.3\system\gwt\java18and282.a6677388\java18and282.cbb23d59\run\www, -logLevel, INFO, -style, OBFUSCATED, com.mySampleApplication.MySampleApplication]
Mär 25, 2019 12:47:21 PM java.util.prefs.WindowsPreferences <init>
WARNING: Could not open/create prefs root node Software\JavaSoft\Prefs at root 0x80000002. Windows RegCreateKeyEx(...) returned error code 5.
Super Dev Mode starting up
   workDir: C:\Users\nicol\AppData\Local\Temp\gwt-codeserver-9053967864514777082.tmp
2019-03-25 12:47:22.461:INFO::main: Logging initialized @2528ms
   Loading Java files in com.mySampleApplication.MySampleApplication.
   Module setup completed in 16450 ms
2019-03-25 12:47:37.943:INFO:oejs.Server:main: jetty-9.2.z-SNAPSHOT
2019-03-25 12:47:37.971:INFO:oejsh.ContextHandler:main: Started o.e.j.s.ServletContextHandler@64dcaf38{/,null,AVAILABLE}
2019-03-25 12:47:37.998:INFO:oejs.ServerConnector:main: Started ServerConnector@184e6e74{HTTP/1.1}{127.0.0.1:9876}
2019-03-25 12:47:37.998:INFO:oejs.Server:main: Started @18064ms

The code server is ready at http://127.0.0.1:9876/
Code server started in 16.78 s ms
Loading modules
   com.mySampleApplication.MySampleApplication
      Validating <servlet> tags for module 'MySampleApplication'
      For additional info see: file:/G:/nicol/Libraries/OneDrive/JavaDevelopment/WebDev/gwt-2.8.2/doc/helpInfo/servletMappings.html
         [WARN] Module declares a servlet class 'com.mySampleApplication.server.MySampleApplicationServiceImpl', but the web.xml has no corresponding declaration; please add the following lines to your web.xml:
<servlet>
  <servlet-name>mySampleApplicationServiceImpl</servlet-name>
  <servlet-class>com.mySampleApplication.server.MySampleApplicationServiceImpl</servlet-class>
</servlet>
<servlet-mapping>
  <servlet-name>mySampleApplicationServiceImpl</servlet-name>
  <url-pattern>/MySampleApplication/MySampleApplicationService</url-pattern>
</servlet-mapping>
2019-03-25 12:47:38.166:INFO:oejs.Server:main: jetty-9.2.z-SNAPSHOT
2019-03-25 12:47:40.252:WARN:/:main: unavailable
javax.servlet.UnavailableException: No class in holder
    at org.eclipse.jetty.servlet.BaseHolder.doStart(BaseHolder.java:88)
    at org.eclipse.jetty.servlet.ServletHolder.doStart(ServletHolder.java:338)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
    at org.eclipse.jetty.servlet.ServletHandler.initialize(ServletHandler.java:870)
    at org.eclipse.jetty.servlet.ServletContextHandler.startContext(ServletContextHandler.java:298)
    at org.eclipse.jetty.webapp.WebAppContext.startWebapp(WebAppContext.java:1349)
    at org.eclipse.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1342)
    at org.eclipse.jetty.server.handler.ContextHandler.doStart(ContextHandler.java:741)
    at org.eclipse.jetty.webapp.WebAppContext.doStart(WebAppContext.java:505)
    at com.google.gwt.dev.shell.jetty.JettyLauncher$WebAppContextWithReload.doStart(JettyLauncher.java:550)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
    at org.eclipse.jetty.util.component.ContainerLifeCycle.start(ContainerLifeCycle.java:132)
    at org.eclipse.jetty.util.component.ContainerLifeCycle.doStart(ContainerLifeCycle.java:114)
    at org.eclipse.jetty.server.handler.AbstractHandler.doStart(AbstractHandler.java:61)
    at org.eclipse.jetty.server.handler.RequestLogHandler.doStart(RequestLogHandler.java:140)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
    at org.eclipse.jetty.util.component.ContainerLifeCycle.start(ContainerLifeCycle.java:132)
    at org.eclipse.jetty.server.Server.start(Server.java:387)
    at org.eclipse.jetty.util.component.ContainerLifeCycle.doStart(ContainerLifeCycle.java:114)
    at org.eclipse.jetty.server.handler.AbstractHandler.doStart(AbstractHandler.java:61)
    at org.eclipse.jetty.server.Server.doStart(Server.java:354)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
    at com.google.gwt.dev.shell.jetty.JettyLauncher.start(JettyLauncher.java:760)
    at com.google.gwt.dev.DevMode.doStartUpServer(DevMode.java:636)
    at com.google.gwt.dev.DevModeBase.startUp(DevModeBase.java:923)
    at com.google.gwt.dev.DevModeBase.run(DevModeBase.java:706)
    at com.google.gwt.dev.DevMode.main(DevMode.java:432)
2019-03-25 12:47:40.253:WARN:oejuc.AbstractLifeCycle:main: FAILED null@5353c376==null,-1,false: javax.servlet.UnavailableException: No class in holder
javax.servlet.UnavailableException: No class in holder
    at org.eclipse.jetty.servlet.BaseHolder.doStart(BaseHolder.java:88)
    at org.eclipse.jetty.servlet.ServletHolder.doStart(ServletHolder.java:338)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
    at org.eclipse.jetty.servlet.ServletHandler.initialize(ServletHandler.java:870)
    at org.eclipse.jetty.servlet.ServletContextHandler.startContext(ServletContextHandler.java:298)
    at org.eclipse.jetty.webapp.WebAppContext.startWebapp(WebAppContext.java:1349)
    at org.eclipse.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1342)
    at org.eclipse.jetty.server.handler.ContextHandler.doStart(ContextHandler.java:741)
    at org.eclipse.jetty.webapp.WebAppContext.doStart(WebAppContext.java:505)
    at com.google.gwt.dev.shell.jetty.JettyLauncher$WebAppContextWithReload.doStart(JettyLauncher.java:550)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
    at org.eclipse.jetty.util.component.ContainerLifeCycle.start(ContainerLifeCycle.java:132)
    at org.eclipse.jetty.util.component.ContainerLifeCycle.doStart(ContainerLifeCycle.java:114)
    at org.eclipse.jetty.server.handler.AbstractHandler.doStart(AbstractHandler.java:61)
    at org.eclipse.jetty.server.handler.RequestLogHandler.doStart(RequestLogHandler.java:140)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
    at org.eclipse.jetty.util.component.ContainerLifeCycle.start(ContainerLifeCycle.java:132)
    at org.eclipse.jetty.server.Server.start(Server.java:387)
    at org.eclipse.jetty.util.component.ContainerLifeCycle.doStart(ContainerLifeCycle.java:114)
    at org.eclipse.jetty.server.handler.AbstractHandler.doStart(AbstractHandler.java:61)
    at org.eclipse.jetty.server.Server.doStart(Server.java:354)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
    at com.google.gwt.dev.shell.jetty.JettyLauncher.start(JettyLauncher.java:760)
    at com.google.gwt.dev.DevMode.doStartUpServer(DevMode.java:636)
    at com.google.gwt.dev.DevModeBase.startUp(DevModeBase.java:923)
    at com.google.gwt.dev.DevModeBase.run(DevModeBase.java:706)
    at com.google.gwt.dev.DevMode.main(DevMode.java:432)
2019-03-25 12:47:40.267:WARN:/:main: unavailable
javax.servlet.UnavailableException: No class in holder
    at org.eclipse.jetty.servlet.BaseHolder.doStart(BaseHolder.java:88)
    at org.eclipse.jetty.servlet.ServletHolder.doStart(ServletHolder.java:338)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
    at org.eclipse.jetty.servlet.ServletHandler.initialize(ServletHandler.java:888)
    at org.eclipse.jetty.servlet.ServletContextHandler.startContext(ServletContextHandler.java:298)
    at org.eclipse.jetty.webapp.WebAppContext.startWebapp(WebAppContext.java:1349)
    at org.eclipse.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1342)
    at org.eclipse.jetty.server.handler.ContextHandler.doStart(ContextHandler.java:741)
    at org.eclipse.jetty.webapp.WebAppContext.doStart(WebAppContext.java:505)
    at com.google.gwt.dev.shell.jetty.JettyLauncher$WebAppContextWithReload.doStart(JettyLauncher.java:550)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
    at org.eclipse.jetty.util.component.ContainerLifeCycle.start(ContainerLifeCycle.java:132)
    at org.eclipse.jetty.util.component.ContainerLifeCycle.doStart(ContainerLifeCycle.java:114)
    at org.eclipse.jetty.server.handler.AbstractHandler.doStart(AbstractHandler.java:61)
    at org.eclipse.jetty.server.handler.RequestLogHandler.doStart(RequestLogHandler.java:140)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
    at org.eclipse.jetty.util.component.ContainerLifeCycle.start(ContainerLifeCycle.java:132)
    at org.eclipse.jetty.server.Server.start(Server.java:387)
    at org.eclipse.jetty.util.component.ContainerLifeCycle.doStart(ContainerLifeCycle.java:114)
    at org.eclipse.jetty.server.handler.AbstractHandler.doStart(AbstractHandler.java:61)
    at org.eclipse.jetty.server.Server.doStart(Server.java:354)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
    at com.google.gwt.dev.shell.jetty.JettyLauncher.start(JettyLauncher.java:760)
    at com.google.gwt.dev.DevMode.doStartUpServer(DevMode.java:636)
    at com.google.gwt.dev.DevModeBase.startUp(DevModeBase.java:923)
    at com.google.gwt.dev.DevModeBase.run(DevModeBase.java:706)
    at com.google.gwt.dev.DevMode.main(DevMode.java:432)
2019-03-25 12:47:40.268:WARN:oejuc.AbstractLifeCycle:main: FAILED null@5353c376==null,-1,false: javax.servlet.UnavailableException: No class in holder
javax.servlet.UnavailableException: No class in holder
    at org.eclipse.jetty.servlet.BaseHolder.doStart(BaseHolder.java:88)
    at org.eclipse.jetty.servlet.ServletHolder.doStart(ServletHolder.java:338)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
    at org.eclipse.jetty.servlet.ServletHandler.initialize(ServletHandler.java:888)
    at org.eclipse.jetty.servlet.ServletContextHandler.startContext(ServletContextHandler.java:298)
    at org.eclipse.jetty.webapp.WebAppContext.startWebapp(WebAppContext.java:1349)
    at org.eclipse.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1342)
    at org.eclipse.jetty.server.handler.ContextHandler.doStart(ContextHandler.java:741)
    at org.eclipse.jetty.webapp.WebAppContext.doStart(WebAppContext.java:505)
    at com.google.gwt.dev.shell.jetty.JettyLauncher$WebAppContextWithReload.doStart(JettyLauncher.java:550)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
    at org.eclipse.jetty.util.component.ContainerLifeCycle.start(ContainerLifeCycle.java:132)
    at org.eclipse.jetty.util.component.ContainerLifeCycle.doStart(ContainerLifeCycle.java:114)
    at org.eclipse.jetty.server.handler.AbstractHandler.doStart(AbstractHandler.java:61)
    at org.eclipse.jetty.server.handler.RequestLogHandler.doStart(RequestLogHandler.java:140)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
    at org.eclipse.jetty.util.component.ContainerLifeCycle.start(ContainerLifeCycle.java:132)
    at org.eclipse.jetty.server.Server.start(Server.java:387)
    at org.eclipse.jetty.util.component.ContainerLifeCycle.doStart(ContainerLifeCycle.java:114)
    at org.eclipse.jetty.server.handler.AbstractHandler.doStart(AbstractHandler.java:61)
    at org.eclipse.jetty.server.Server.doStart(Server.java:354)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
    at com.google.gwt.dev.shell.jetty.JettyLauncher.start(JettyLauncher.java:760)
    at com.google.gwt.dev.DevMode.doStartUpServer(DevMode.java:636)
    at com.google.gwt.dev.DevModeBase.startUp(DevModeBase.java:923)
    at com.google.gwt.dev.DevModeBase.run(DevModeBase.java:706)
    at com.google.gwt.dev.DevMode.main(DevMode.java:432)
Starting Jetty on port 8888
   [WARN] Failed startup of context c.g.g.d.s.j.WebAppContextWithReload@30de9fe5{/,file:/C:/Users/nicol/.IntelliJIdea2018.3/system/gwt/java18and282.a6677388/java18and282.cbb23d59/run/www/,STARTING}{C:\Users\nicol\.IntelliJIdea2018.3\system\gwt\java18and282.a6677388\java18and282.cbb23d59\run\www}
MultiException[javax.servlet.UnavailableException: No class in holder, javax.servlet.UnavailableException: No class in holder]
    at org.eclipse.jetty.servlet.ServletHandler.initialize(ServletHandler.java:842)
    at org.eclipse.jetty.servlet.ServletContextHandler.startContext(ServletContextHandler.java:298)
    at org.eclipse.jetty.webapp.WebAppContext.startWebapp(WebAppContext.java:1349)
    at org.eclipse.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1342)
    at org.eclipse.jetty.server.handler.ContextHandler.doStart(ContextHandler.java:741)
    at org.eclipse.jetty.webapp.WebAppContext.doStart(WebAppContext.java:505)
    at com.google.gwt.dev.shell.jetty.JettyLauncher$WebAppContextWithReload.doStart(JettyLauncher.java:550)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
    at org.eclipse.jetty.util.component.ContainerLifeCycle.start(ContainerLifeCycle.java:132)
    at org.eclipse.jetty.util.component.ContainerLifeCycle.doStart(ContainerLifeCycle.java:114)
    at org.eclipse.jetty.server.handler.AbstractHandler.doStart(AbstractHandler.java:61)
    at org.eclipse.jetty.server.handler.RequestLogHandler.doStart(RequestLogHandler.java:140)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
    at org.eclipse.jetty.util.component.ContainerLifeCycle.start(ContainerLifeCycle.java:132)
    at org.eclipse.jetty.server.Server.start(Server.java:387)
    at org.eclipse.jetty.util.component.ContainerLifeCycle.doStart(ContainerLifeCycle.java:114)
    at org.eclipse.jetty.server.handler.AbstractHandler.doStart(AbstractHandler.java:61)
    at org.eclipse.jetty.server.Server.doStart(Server.java:354)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
    at com.google.gwt.dev.shell.jetty.JettyLauncher.start(JettyLauncher.java:760)
    at com.google.gwt.dev.DevMode.doStartUpServer(DevMode.java:636)
    at com.google.gwt.dev.DevModeBase.startUp(DevModeBase.java:923)
    at com.google.gwt.dev.DevModeBase.run(DevModeBase.java:706)
    at com.google.gwt.dev.DevMode.main(DevMode.java:432)
    Suppressed: javax.servlet.UnavailableException: No class in holder
        at org.eclipse.jetty.servlet.BaseHolder.doStart(BaseHolder.java:88)
        at org.eclipse.jetty.servlet.ServletHolder.doStart(ServletHolder.java:338)
        at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
        at org.eclipse.jetty.servlet.ServletHandler.initialize(ServletHandler.java:888)
        ... 23 more
Caused by: javax.servlet.UnavailableException: No class in holder
    at org.eclipse.jetty.servlet.BaseHolder.doStart(BaseHolder.java:88)
    at org.eclipse.jetty.servlet.ServletHolder.doStart(ServletHolder.java:338)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
    at org.eclipse.jetty.servlet.ServletHandler.initialize(ServletHandler.java:870)
    ... 23 more
2019-03-25 12:47:40.272:INFO:oejs.ServerConnector:main: Started ServerConnector@14ff45c2{HTTP/1.1}{127.0.0.1:8888}
2019-03-25 12:47:40.273:INFO:oejs.Server:main: Started @20339ms
Dev Mode initialized. Startup URL: 
http://127.0.0.1:8888/MySampleApplication.html
[ERROR] 503 - GET /MySampleApplication.html (127.0.0.1) 312 bytes
   Request headers
      Host: 127.0.0.1:8888
      User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:65.0) Gecko/20100101 Firefox/65.0
      Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
      Accept-Language: de,en-US;q=0.7,en;q=0.3
      Accept-Encoding: gzip, deflate
      DNT: 1
      Connection: keep-alive
      Upgrade-Insecure-Requests: 1
   Response headers
      Date: Mon, 25 Mar 2019 11:47:41 GMT
      Cache-Control: must-revalidate,no-cache,no-store
      Content-Type: text/html; charset=ISO-8859-1
      Content-Length: 312

【问题讨论】：

您使用的是 Java 9 或更高版本吗？模块系统可能不得不对这些错误做些什么。尝试使用 JDK 8。
最初我使用的是 Java 11，但使用 Java 8 我在 2.7.0 和 2.8.2 中都遇到了 HTTP 503 错误：/
但是还是ClassNotFoundException: sun.misc.GC造成的吗？还是其他错误？
我不这么认为，我更新了错误消息，两者都使用 java 1.8 但使用 gwt 2.7.0 和 2.8.2 时错误消息似乎不同，但结果仍然相同, 都打开一个 HTTP 503 页面
作为预防措施，提取的gwt文件夹不需要在项目文件夹中对吗？我只需要将 intelliJ 中的路径设置为 gwt 根文件夹

标签： java intellij-idea gwt

【解决方案1】：

问题似乎是 IntelliJ 创建的“示例 GWT 项目”缺少 web.xml 文件中的 servlet 声明，正如您在日志中收到的警告所注意到的那样：

[WARN] 模块声明了一个servlet类'com.mySampleApplication.server.MySampleApplicationServiceImpl'，但是web.xml中没有对应的声明；请将以下几行添加到您的 web.xml：
<servlet> <servlet-name>mySampleApplicationServiceImpl</servlet-name> <servlet-class>com.mySampleApplication.server.MySampleApplicationServiceImpl</servlet-class> </servlet> <servlet-mapping> <servlet-name>mySampleApplicationServiceImpl</servlet-name> <url-pattern>/MySampleApplication/MySampleApplicationService</url-pattern> </servlet-mapping>

经过检查，我可以确认 IntelliJ 生成的web.xml 是这样的：

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">
    <servlet/>
</web-app>

因此，您需要添加日志中提到的行才能使其正常工作：

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">
    <servlet>
        <servlet-name>mySampleApplicationServiceImpl</servlet-name>
        <servlet-class>com.mySampleApplication.server.MySampleApplicationServiceImpl</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>mySampleApplicationServiceImpl</servlet-name>
        <url-pattern>/MySampleApplication/MySampleApplicationService</url-pattern>
    </servlet-mapping>
</web-app>

作为参考，对比GWT SDK的webAppCreator命令创建的示例web.xml，不存在这个问题：

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
              http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
         version="2.5"
         xmlns="http://java.sun.com/xml/ns/javaee">

  <!-- Servlets -->
  <servlet>
    <servlet-name>greetServlet</servlet-name>
    <servlet-class>com.example.server.GreetingServiceImpl</servlet-class>
  </servlet>

  <servlet-mapping>
    <servlet-name>greetServlet</servlet-name>
    <url-pattern>/stockwatcher/greet</url-pattern>
  </servlet-mapping>

  <!-- Default page to serve -->
  <welcome-file-list>
    <welcome-file>StockWatcher.html</welcome-file>
  </welcome-file-list>

</web-app>

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