使用JSF时,http GET参数有时会丢失

JSF

如果检测到错误,用户将被重定向到错误页面,在那里他可以给出反馈。然后我尝试读取 ErrorBean 对象然而,有时错误并不存在——存在错误的可能性为50%。

FacesContext.getCurrentInstance().getExternalContext().getRequestParameterMap()

它有时返回一个带有1个条目的映射,有时返回一个空映射。在任何情况下,id都是在http级别传递的。

我真的无法重现是什么导致了这一切。以下是相关代码(省略了helper方法+空实现)。ErrorFilter映射在 /* ErrorBean是由JSF管理的会话范围bean。

public class ErrorFilter implements Filter 
{
  public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException 
  {
    HttpServletRequest hreq = (HttpServletRequest) req;
    HttpServletResponse hres = (HttpServletResponse) resp;

    try 
    {
      chain.doFilter(req, resp);
    } 
    catch (IOException e) 
    {
      handleError(e, hreq, hres);
    } 
    catch (ServletException e) 
    {
      handleError(e, hreq, hres);
    } 
    catch (RuntimeException e) 
    {
      handleError(e, hreq, hres);
    }
  }

  private static void handleError(Throwable e, HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException 
  {
    final RequestInfo requestInfo = new RequestInfo(getUri(req), req.getSession().getId(), null, null, UserFactory.getUser(), InetAddress.getByName(req.getRemoteAddr()));
    String token = new DecimalFormat("00000000").format(Math.abs(RANDOM.nextInt() % Integer.MAX_VALUE));
    //log msg
    //send mail in a different thread

    if (!req.getRequestURI().startsWith("/faces/error.jsp")) 
    {
      resp.sendRedirect("/faces/error.jsp?token=" + token);
    } 
    else 
    {
      //log that an infite loop occurred
      throw new ServletException(crapMsg, e);
    }
  }
}

错误豆

public class ErrorBean implements Serializable 
{
  private String feedback;
  private String lastToken;

  public String getLastErrorCode() 
  {
    return "your token: " + getToken();
  }

  private String getToken() 
  {
    final String token = (String) FacesContext.getCurrentInstance().getExternalContext().getRequestParameterMap().get("token");
    //here the "token" returns null although it is sent via get.

    if (token != null) 
    {
        if (!token.equals(lastToken)) 
        {
          // reset data on token change.
          feedback = null;
        }
        lastToken = token;
    }

    return lastToken;
  }

  public void setFeedback(String feedback) 
  {
    this.feedback = feedback;
  }

    public String getFeedback() 
    {
      if (feedback == null) 
      {
        feedback = getDefaultMessage();
      }

      return feedback;
    }

  public void send()
  {
    sendMail(lastToken,feedback);
  }
}