相关疑难解决方法(0)

我是servlet的新手,并阅读有关过滤器和包装器的一些文本.我可以理解过滤器,但对包装器感到困惑.在书中,作者给出了一个例子:

如果没有包装:

public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain)
            throws IOException, ServletException {

        String name = request.getParameter("name").trim();

        try {
            chain.doFilter(request, response);
            PrintWriter out = response.getWriter();
            if (name.length() == 0) {
                out.println("Some message");
                out.println("</body>");
                out.println("</html>");
                out.close();
            }
        } catch (Throwable t) {
        }
    }

如果是包装:

 public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain)
            throws IOException, ServletException {

        String name = request.getParameter("name").trim();

        HttpServletResponse httpRes = (HttpServletResponse) response;
        HttpServletResponseWrapper resWrapper = new HttpServletResponseWrapper(httpRes);
        try {
            chain.doFilter(request, response);

            PrintWriter out = resWrapper.getWriter(); // …

这是与Capture相关的问题并记录响应正文.如果我只想记录响应头而不是整个身体怎么办？是否有与链接问题中描述的方法不同的方法？