用于缓存的Servlet过滤器 [英] Servlet filter for caching

问题描述

我正在为缓存创建一个servlet过滤器。想法是将响应主体缓存到memcached。响应体由（结果是字符串）生成：

  response.getWriter（）。print（result）; 
  

我的问题是，由于响应正文将被放入memcached而不做修改，我还能需要创建一个自定义的HttpServletResponseWrapper？任何人都可以为此过滤器提供任何框架代码吗？

解决方案

您需要能够在过滤器中捕获servlet的输出。 / p>

为此，您需要注入一个自定义的HttpServletResponseWrapper，它收集发送到 getWriter（）的所有输出.print（）在某个地方，你可以把它交给memcached。

也许是这样的：

  ByteArrayOutputStream baos = new ByteArrayOutputStream（3000）; 
 final PrintWriter w = new PrintWriter（new OutputStreamWriter（baos，UTF-8））; 
 
 HttpServletResponse wrapper = new HttpServletResponseWrapper（response）{
 
 @Override 
 public PrintWriter getWriter（）抛出IOException {
 return w; 
} 
 
}; 
  

如果这是一个更大的项目，你可以更好地控制网络基础设施，它也可能是一个最好不要在Java中执行此操作，而只需在Servlet容器前使用单独的代理服务器。您可以控制通常的缓存控制标头缓存的内容（如果servlet尚未使用过滤器，您可以使用过滤器进行设置）。

I'm creating a servlet filter for caching. The idea is to cache the response body to memcached. The response body is generated by (result is a string):

 response.getWriter().print(result);

My question is that, since the response body will be put into the memcached without modification, do I still need to create a customized HttpServletResponseWrapper? Can anyone provide any skeleton code for this filter?

解决方案

You need to be able to capture the servlet's output in your filter.

For this, you need to inject a customized HttpServletResponseWrapper that collects all output sent to getWriter().print() somewhere so that you can hand it off to memcached.

Maybe something along the lines of:

  ByteArrayOutputStream baos = new ByteArrayOutputStream(3000); 
  final PrintWriter w = new PrintWriter(new OutputStreamWriter(baos, "UTF-8"));

  HttpServletResponse wrapper = new HttpServletResponseWrapper(response) {

                        @Override
                        public PrintWriter getWriter() throws IOException {
                            return w;
                        }

                    };

If this is a bigger project and you have more control over the network infrastructure, it might also be a good idea to not do this in Java, but just use a separate proxy server in front of the Servlet container. You can control what should be cached by the usual cache-control headers (which you can set using a filter if the servlet does not already do it).

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