[疑难杂症]Filter会影响配置？

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今天上课讲到一个web应用时，随口提起异常、错误集中处理显示，自然地想到了web.xml配置文件中的项，进而在一个servlet中应用了一下。如下：
web.xml加入如下配置
 
    javax.servlet.ServletException
    /error.jsp
 
servlet中加入异常抛出代码
String title=request.getParameter("title");
if(title==null || title.trim().equals(""))
    throw new ServletException("请输入数据");
启动运行，页面一片空白！？怎么回事，难道没有进入error.jsp？仔细查了查看到控制台报的异常中有一处是EncodingFilter的代码位置，难道和过滤器有关？！于是屏蔽了过滤器再启动服务运行，一切OK了！果真和过滤器有关，翻开servlet-2.4手册查到一段说明：
The error page mechanism described does not intervene when errors occur
when invoked using the RequestDispatcher or filter.doFilter method. In this
way, a filter or servlet using the RequestDispatcher has the opportunity to handle
errors generated.
回头再认真看了看抛出的异常位置，是在过滤器的doFilter()方法调用处，恍然大悟，doFilter()调用被try-catch了，过滤器自己catch(ServletException)进行了处理，所以不会再转到error.jsp页面。最后想了个解决方法：
       try {          
            filterChain.doFilter(request, response);
        }catch (ServletException sx) {
            filterConfig.getServletContext().log(sx.getMessage());
            request.setAttribute("errMsg",sx.getMessage());
            RequestDispatcher rd=request.getRequestDispatcher("/error.jsp");
            try {
                rd.forward(request, response);
            } catch (Exception ex) {
               filterConfig.getServletContext().log(ex.getMessage());
            }
        } catch (IOException iox) {
            filterConfig.getServletContext().log(iox.getMessage());
        }