那些遇到过的问题

为什么Tomcat服务器不使用web.xml文件作为Vaadin 7应用程序中使用的servlet配置？

ton*_*nix 7 java tomcat web.xml servlets vaadin

当我使用web.xml作为应用程序中servlet的配置文件时,我无法启动Tomcat,这是文件的内容:

<?xml version="1.0" encoding="UTF-8"?>
<web-app
  id="WebApp_ID" version="3.0"
  xmlns="http://java.sun.com/xml/ns/j2ee" 
  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_3_0.xsd">

  <servlet>
    <servlet-name>AppLifeServlet</servlet-name>
    <servlet-class>
        com.example.application_lifecycle_chapter_4_7.ApplicatationLifecycleUI.Servlet
    </servlet-class>
    <init-param>
      <param-name>UI</param-name>
      <param-value>com.example.application_lifecycle_chapter_4_7.ApplicationLifecycleUI</param-value>
    </init-param>
    <async-supported>true</async-supported>
  </servlet>

  <servlet>
      <servlet-name>MyPushyServlet</servlet-name>
      <servlet-class>
          com.example.application_lifecycle_chapter_4_7.MyPushyUI.Servlet
      </servlet-class>
      <init-param>
        <param-name>UI</param-name>
        <param-value>com.example.application_lifecycle_chapter_4_7.MyPushyUI</param-value>
      </init-param>
      <async-supported>true</async-supported>
  </servlet>    

  <servlet-mapping>
    <servlet-name>AppLifeServlet</servlet-name>
    <url-pattern>/AppLife/*</url-pattern>
  </servlet-mapping>

  <servlet-mapping>
      <servlet-name>AppLifeServlet</servlet-name>
      <url-pattern>/VAADIN/*</url-pattern>
  </servlet-mapping>

  <servlet-mapping>
      <servlet-name>MyPushyServlet</servlet-name>
      <url-pattern>/MyPushyUI/*</url-pattern>
  </servlet-mapping>
</web-app>
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为什么不起作用？Tomcat甚至无法启动,而是返回异常:

SEVERE: Failed to destroy end point associated with ProtocolHandler ["ajp-nio-8009"]
java.lang.NullPointerException
    at org.apache.tomcat.util.net.NioEndpoint.releaseCaches(NioEndpoint.java:307)
    at org.apache.tomcat.util.net.NioEndpoint.unbind(NioEndpoint.java:482)
    at org.apache.tomcat.util.net.AbstractEndpoint.destroy(AbstractEndpoint.java:795)
    at org.apache.coyote.AbstractProtocol.destroy(AbstractProtocol.java:531)
    at org.apache.catalina.connector.Connector.destroyInternal(Connector.java:1023)
    at org.apache.catalina.util.LifecycleBase.destroy(LifecycleBase.java:305)
    at org.apache.catalina.core.StandardService.destroyInternal(StandardService.java:588)
    at org.apache.catalina.util.LifecycleBase.destroy(LifecycleBase.java:305)
    at org.apache.catalina.core.StandardServer.destroyInternal(StandardServer.java:850)
    at org.apache.catalina.util.LifecycleBase.destroy(LifecycleBase.java:305)
    at org.apache.catalina.startup.Catalina.start(Catalina.java:629)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:351)
    at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:485)
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如果我禁用web.xml并使用Servlet的3.0 API注释一切正常......

web.xml文件有什么问题？

编辑:这是Tomcat尝试启动时的完整异常输出:

SEVERE: A child container failed during start
java.util.concurrent.ExecutionException: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/Application_Lifecycle_Chapter_4.7]]
    at java.util.concurrent.FutureTask.report(FutureTask.java:122)
    at java.util.concurrent.FutureTask.get(FutureTask.java:192)
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:917)
    at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:868)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1409)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1399)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/Application_Lifecycle_Chapter_4.7]]
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:154)
    ... 6 more
Caused by: java.lang.IllegalArgumentException: The servlets named [AppLifeServlet] and [com.example.application_lifecycle_chapter_4_7.ApplicationLifecycleUI$Servlet] are both mapped to the url-pattern [/AppLife/*] which is not permitted
    at org.apache.tomcat.util.descriptor.web.WebXml.addServletMapping(WebXml.java:308)
    at org.apache.catalina.startup.ContextConfig.processAnnotationWebServlet(ContextConfig.java:2325)
    at org.apache.catalina.startup.ContextConfig.processAnnotationsStream(ContextConfig.java:2007)
    at org.apache.catalina.startup.ContextConfig.processAnnotationsWebResource(ContextConfig.java:1901)
    at org.apache.catalina.startup.ContextConfig.processAnnotationsWebResource(ContextConfig.java:1896)
    at org.apache.catalina.startup.ContextConfig.processAnnotationsWebResource(ContextConfig.java:1896)
    at org.apache.catalina.startup.ContextConfig.processAnnotationsWebResource(ContextConfig.java:1896)
    at org.apache.catalina.startup.ContextConfig.webConfig(ContextConfig.java:1139)
    at org.apache.catalina.startup.ContextConfig.configureStart(ContextConfig.java:771)
    at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:305)
    at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:117)
    at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:90)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5095)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    ... 6 more

Dec 07, 2014 7:49:30 PM org.apache.catalina.core.ContainerBase startInternal
SEVERE: A child container failed during start
java.util.concurrent.ExecutionException: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost]]
    at java.util.concurrent.FutureTask.report(FutureTask.java:122)
    at java.util.concurrent.FutureTask.get(FutureTask.java:192)
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:917)
    at org.apache.catalina.core.StandardEngine.startInternal(StandardEngine.java:262)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    at org.apache.catalina.core.StandardService.startInternal(StandardService.java:439)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    at org.apache.catalina.core.StandardServer.startInternal(StandardServer.java:760)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    at org.apache.catalina.startup.Catalina.start(Catalina.java:625)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:351)
    at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:485)
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost]]
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:154)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1409)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1399)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)
Caused by: org.apache.catalina.LifecycleException: A child container failed during start
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:925)
    at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:868)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    ... 6 more

Dec 07, 2014 7:49:30 PM org.apache.catalina.startup.Catalina start
SEVERE: The required Server component failed to start so Tomcat is unable to start.
org.apache.catalina.LifecycleException: Failed to start component [StandardServer[8005]]
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:154)
    at org.apache.catalina.startup.Catalina.start(Catalina.java:625)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:351)
    at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:485)
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardService[Catalina]]
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:154)
    at org.apache.catalina.core.StandardServer.startInternal(StandardServer.java:760)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    ... 7 more
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina]]
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:154)
    at org.apache.catalina.core.StandardService.startInternal(StandardService.java:439)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    ... 9 more
Caused by: org.apache.catalina.LifecycleException: A child container failed during start
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:925)
    at org.apache.catalina.core.StandardEngine.startInternal(StandardEngine.java:262)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    ... 11 more

Dec 07, 2014 7:49:30 PM org.apache.coyote.AbstractProtocol pause
INFO: Pausing ProtocolHandler ["http-nio-8080"]
Dec 07, 2014 7:49:30 PM org.apache.coyote.AbstractProtocol pause
INFO: Pausing ProtocolHandler ["ajp-nio-8009"]
Dec 07, 2014 7:49:30 PM org.apache.catalina.core.StandardService stopInternal
INFO: Stopping service Catalina
Dec 07, 2014 7:49:30 PM org.apache.coyote.AbstractProtocol destroy
INFO: Destroying ProtocolHandler ["http-nio-8080"]
Dec 07, 2014 7:49:30 PM org.apache.coyote.AbstractProtocol destroy
SEVERE: Failed to destroy end point associated with ProtocolHandler ["http-nio-8080"]
java.lang.NullPointerException
    at org.apache.tomcat.util.net.NioEndpoint.releaseCaches(NioEndpoint.java:307)
    at org.apache.tomcat.util.net.NioEndpoint.unbind(NioEndpoint.java:482)
    at org.apache.tomcat.util.net.AbstractEndpoint.destroy(AbstractEndpoint.java:795)
    at org.apache.coyote.AbstractProtocol.destroy(AbstractProtocol.java:531)
    at org.apache.catalina.connector.Connector.destroyInternal(Connector.java:1023)
    at org.apache.catalina.util.LifecycleBase.destroy(LifecycleBase.java:305)
    at org.apache.catalina.core.StandardService.destroyInternal(StandardService.java:588)
    at org.apache.catalina.util.LifecycleBase.destroy(LifecycleBase.java:305)
    at org.apache.catalina.core.StandardServer.destroyInternal(StandardServer.java:850)
    at org.apache.catalina.util.LifecycleBase.destroy(LifecycleBase.java:305)
    at org.apache.catalina.startup.Catalina.start(Catalina.java:629)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:351)
    at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:485)

Dec 07, 2014 7:49:30 PM org.apache.coyote.AbstractProtocol destroy
INFO: Destroying ProtocolHandler ["ajp-nio-8009"]
Dec 07, 2014 7:49:30 PM org.apache.coyote.AbstractProtocol destroy
SEVERE: Failed to destroy end point associated with ProtocolHandler ["ajp-nio-8009"]
java.lang.NullPointerException
    at org.apache.tomcat.util.net.NioEndpoint.releaseCaches(NioEndpoint.java:307)
    at org.apache.tomcat.util.net.NioEndpoint.unbind(NioEndpoint.java:482)
    at org.apache.tomcat.util.net.AbstractEndpoint.destroy(AbstractEndpoint.java:795)
    at org.apache.coyote.AbstractProtocol.destroy(AbstractProtocol.java:531)
    at org.apache.catalina.connector.Connector.destroyInternal(Connector.java:1023)
    at org.apache.catalina.util.LifecycleBase.destroy(LifecycleBase.java:305)
    at org.apache.catalina.core.StandardService.destroyInternal(StandardService.java:588)
    at org.apache.catalina.util.LifecycleBase.destroy(LifecycleBase.java:305)
    at org.apache.catalina.core.StandardServer.destroyInternal(StandardServer.java:850)
    at org.apache.catalina.util.LifecycleBase.destroy(LifecycleBase.java:305)
    at org.apache.catalina.startup.Catalina.start(Catalina.java:629)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:351)
    at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:485)
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决议:这是关键路线:

 Caused by: java.lang.IllegalArgumentException: The servlets named [AppLifeServlet] and 
    [com.example.application_lifecycle_chapter_4_7.ApplicationLifecycleUI$Servlet] are both 
    mapped to the url-pattern [/AppLife/*] which is not permitted
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从Vaadin书:

您可以在同一个应用程序中同时使用web.xml和WebServlet.web.xml中的设置会覆盖注释中给出的设置.

这不是真的!在我的情况下,错误是由于这句话:我在web.xml文件中的servlet映射中有一个@WebServlet注释ApplicationLifecycleUI$Servlet.

这两个配置不能共存,因此您必须选择是否对@WebServletURL映射使用web.xml或注释,否则在尝试启动Tomcat时会出现此错误.

小智 5

我发现@tonix 的评论实际上是正确的。注解和 web.xml 不能共存。如果您想保留注释，您只需删除 web.xml。

此外，只需检查您的所有 url-pattern 是在 web.xml 中还是在注释中，它们应该是正确的，我的意思是通常它们应该以“/”（正斜杠）为前缀。

进行这些更改后，尝试重新启动 tomcat，它应该可以工作，这在我非常相似的情况下也是如此。

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