Capture sensitive character of the application of filters

Ideas: in the jsp settings form, the form Jump to access the servlet, but the middle of the filter, the filter is provided with a sensitive word to intercept
sensitive word then prompts the user to jump to another page, the word is not sensitive to the normal jump to the servlet.

Procedure:
     1.jsp of:

<form action="comment.do">
       username:<input type="text" name="username"/>
       comment:<textarea name="comment"></textarea>
       <button>提交评论</button>
  </form>

      2. doFilter filter's method:
 

        // set the character set
         // not garbled page from the character input 
        Request.setCharacterEncoding ( "UTF-. 8" );
         // character output from the servlet does not garbled 
        response.setContentType ( "text / html; charset = utf- 8 " );
         // acquisition request parameter 
        String = request.getParameter keyword (" Comment " ); 
        System.out.println (keyword); 
        IF (keyword.contains (" XXX ")! = & keyword null ) {
             // Note: It is not the HttpServletRequest HttpServletResponse
             // and ServletResponse is HttpServletResponse parent 
            HttpServletResponse RESP = (HttpServletResponse) Response;
            // Redirect jump page 
            resp.sendRedirect ( "the error.jsp" ); 
        } the else { 
            the chain.doFilter (Request, Response); 
        } 
    }

 

 

3. The existence of sensitive words jump page error.jsp, the contents of self

4. there is no sensitive words, normal jump to the servlet, self-made content