java - 网页长时间打开抛出空指针异常

Question

我正在使用 Apache - tomcat 5.5 作为服务器使用 JSP 和 Servlet 开发一个网站。我的应用程序运行良好。但是每当我打开任何网页并在一段时间后返回它时说 30 分钟，然后单击任何按钮或图标，它都会抛出错误说 -

Sep 16, 2011 2:11:33 PM org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet jsp threw exception
java.lang.NullPointerException
    at org.apache.jsp.homepage_jsp._jspService(homepage_jsp.java:107)
    at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:98)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:369)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:308)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:259)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:172)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:108)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:174)
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:879)
    at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:665)
    at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:528)
    at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:81)
    at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:689)
    at java.lang.Thread.run(Unknown Source)

Answer 1

听起来您的 session 超时了。您需要强制用户重新登录，或延长 session 超时时间。

您可以通过编辑 web.xml 并添加以下内容来更改 session 超时:

<session-config>
  <session-timeout>60</session-timeout>
</session-config>

这将为您提供 60 分钟的 session 超时。 -1 表示没有超时。