org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter cannot be cast to javax.servlet.Servlet异常处理

前言:

　　在构建一个新的struts2项目时,在web.xml中添加上struts的核心过滤器后报了这样一个异常:

java.lang.ClassCastException: org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter cannot be cast to javax.servlet.Servlet
    at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1146)
    at org.apache.catalina.core.StandardWrapper.allocate(StandardWrapper.java:866)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:134)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:505)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:169)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:956)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:436)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1078)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:625)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:745)

处理方式:

　　仔细看了一下web.xml中struts核心过滤器的配置内容如下:

  <servlet>
      <servlet-name>struts2</servlet-name>
      <servlet-class>org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter</servlet-class>
  </servlet>
  <servlet-mapping>
      <servlet-name>struts2</servlet-name>
      <url-pattern>/*</url-pattern>
  </servlet-mapping>

　　这种配置是错误的,原因:StrutsPrepareAndExecuteFilter是过滤器,不应该使用servlet标签,而应该使用filter标签

　　改正如下:

  <filter>
      <filter-name>struts2</filter-name>
      <filter-class>org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter</filter-class>
  </filter>
  <filter-mapping>
      <filter-name>struts2</filter-name>
      <url-pattern>/*</url-pattern>
  </filter-mapping>