java / jsf奇怪的錯誤：警告：StandardWrapperValve PWC1406：Servlet.service（）...拋出異常java.lang.NullPointerException

Question

我有簡單的jsf應用程序與servlet動態圖像和過濾器設置utf8編碼。 不時（1/10請求）我得到非常奇怪的錯誤：

WARNING: StandardWrapperValve[com.webapp.servlet.ImageServlet]: PWC1406: Servlet.service() for servlet com.webapp.servlet.ImageServlet threw exception
java.lang.NullPointerException
    at com.sun.enterprise.v3.services.impl.monitor.MonitorableSelectionKeyHandler$CloseHandler.notifyClosed(MonitorableSelectionKeyHandler.java:94)
    at com.sun.enterprise.v3.services.impl.monitor.MonitorableSelectionKeyHandler$CloseHandler.remotlyClosed(MonitorableSelectionKeyHandler.java:90)
    at com.sun.grizzly.BaseSelectionKeyHandler.notifyRemotlyClose(BaseSelectionKeyHandler.java:233)
    at com.sun.grizzly.util.OutputWriter.notifyRemotelyClosed(OutputWriter.java:353)
    at com.sun.grizzly.util.OutputWriter.flushChannel(OutputWriter.java:148)
    at com.sun.grizzly.util.OutputWriter.flushChannel(OutputWriter.java:76)
    at com.sun.grizzly.http.SocketChannelOutputBuffer.flushChannel(SocketChannelOutputBuffer.java:326)
    at com.sun.grizzly.http.SocketChannelOutputBuffer.flushBuffer(SocketChannelOutputBuffer.java:398)
    at com.sun.grizzly.http.SocketChannelOutputBuffer.flush(SocketChannelOutputBuffer.java:376)
    at com.sun.grizzly.http.ProcessorTask.action(ProcessorTask.java:1247)
    at com.sun.grizzly.tcp.Response.action(Response.java:268)
    at org.apache.catalina.connector.OutputBuffer.doFlush(OutputBuffer.java:380)
    at org.apache.catalina.connector.OutputBuffer.flush(OutputBuffer.java:353)
    at org.apache.catalina.connector.CoyoteOutputStream.flush(CoyoteOutputStream.java:175)
*   at com.webapp.servlet.ImageServlet.doGet(ImageServlet.java:35)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:734)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:847)
    at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1539)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:343)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:217)
    at com.ocpsoft.pretty.PrettyFilter.doFilter(PrettyFilter.java:118)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:256)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:217)
*   at com.webapp.filter.CharacterEncodingFilter.doFilter(CharacterEncodingFilter.java:32)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:256)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:217)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:279)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
    at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:655)
    at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:595)
    at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:98)
    at com.sun.enterprise.web.PESessionLockingStandardPipeline.invoke(PESessionLockingStandardPipeline.java:91)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:162)
    at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:330)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:231)
    at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:174)
    at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:828)
    at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:725)
    at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:1019)
    at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:225)
    at com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:137)
    at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:104)
    at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:90)
    at com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:79)
    at com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:54)
    at com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:59)
    at com.sun.grizzly.ContextTask.run(ContextTask.java:71)
    at com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:532)
    at com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:513)
    at java.lang.Thread.run(Thread.java:722)

這是我的servlet和過濾器，我標有引用stacktrace的星號行：

@WebServlet(urlPatterns = "/images/*")
public class ImageServlet extends HttpServlet {

  @Inject
  private FileService fileService;

  @Override
  public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
      byte[] img = fileService.getImage(request.getPathInfo());
      if (img != null) {
        response.setContentType("image/png");
        response.addHeader("Content-Length", String.valueOf(img.length));
        ServletOutputStream os = response.getOutputStream();
          os.write(img);
*         os.flush();
          os.close();
      } else {
        response.sendRedirect(request.getContextPath() + "/error");
      }
  }
}


@WebFilter(urlPatterns = "/*")
public class CharacterEncodingFilter implements Filter {

  @Override
  public void init(FilterConfig filterConfig) {
  }

  @Override
  public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
    request.setCharacterEncoding("UTF-8");
    response.setCharacterEncoding("UTF-8");
*   chain.doFilter(request, response);
  }

  @Override
  public void destroy() {
  }
}

我完全不知道發生了什么......我正在使用帶有jdk7的Glassfish 3.1.1 web profile

Answer 1

關閉流時已隱式執行刷新。 關閉已經由容器本身隱式完成。 實際上，你不需要自己做。 但是，大多數servlet開發人員都會對他們忽略的情況進行早期反饋，即請求 - 響應鏈中的其他內容正在寫入輸出流，例如錯誤的過濾器或響應包裝器等。 這將導致每次調用都發生IOException ，因為流已關閉。

在任何情況下，您有2個選項來處理flush()和close() ：

1. 將它們放在try-catch ，您可以忽略該異常。
2. 刪除這兩行。 無論如何，容器會為你做這件事。 它也會忽略異常。

此異常僅表示客戶端中止了連接。 例如，按下[Esc]或關閉窗口/標簽，或在圖像仍然流式傳輸時導航到另一個頁面。

也可以看看：

• 我應該關閉servlet輸出流嗎？

Answer 2

at com.sun.grizzly.util.OutputWriter.notifyRemotelyClosed()

不知何故，這看起來好像你正在刷新流的連接已經被遠程對等體（Web瀏覽器？）中間關閉了。

你可以嘗試使用response.flushBuffer() 。 這也會拋出異常嗎？