无法在java中使用cachingHttpClient缓存HttpResponse？

Question

我正在尝试使用cachingHttpClient缓存HTTP响应,但是徒劳无功.这是我通过参考这个链接放在一起的演示,http://hc.apache.org/httpcomponents-client-ga/tutorial/html/caching.html

  public class CacheDemo {

    public static void main(String[] args) {
        CacheConfig cacheConfig = new CacheConfig();
        cacheConfig.setMaxCacheEntries(1000);
        cacheConfig.setMaxObjectSizeBytes(1024 * 1024);

        HttpClient cachingClient = new CachingHttpClient(new DefaultHttpClient(), cacheConfig);

        HttpContext localContext = new BasicHttpContext();

        sendRequest(cachingClient, localContext);
        CacheResponseStatus responseStatus = (CacheResponseStatus) localContext.getAttribute(
                CachingHttpClient.CACHE_RESPONSE_STATUS);
        checkResponse(responseStatus);


        sendRequest(cachingClient, localContext);
        responseStatus = (CacheResponseStatus) localContext.getAttribute(
                CachingHttpClient.CACHE_RESPONSE_STATUS);
        checkResponse(responseStatus);
    }

    static void sendRequest(HttpClient cachingClient, HttpContext localContext) {
        HttpGet httpget = new HttpGet("http://www.mydomain.com/content/");
        HttpResponse response = null;
        try {
            response = cachingClient.execute(httpget, localContext);
        } catch (ClientProtocolException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        } catch (IOException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        }
        HttpEntity entity = response.getEntity();
        try {
            EntityUtils.consume(entity);
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }

    static void checkResponse(CacheResponseStatus responseStatus) {
        switch (responseStatus) {
            case CACHE_HIT:
                System.out.println("A response was generated from the cache with no requests "
                        + "sent upstream");
                break;
            case CACHE_MODULE_RESPONSE:
                System.out.println("The response was generated directly by the caching module");
                break;
            case CACHE_MISS:
                System.out.println("The response came from an upstream server");
                break;
            case VALIDATED:
                System.out.println("The response was generated from the cache after validating "
                        + "the entry with the origin server");
                break;
        }
    }

  }

它是一个简单的程序,但我无法弄清楚我哪里出错了.非常感谢您的帮助.谢谢.

Answer 1

url http://www.mydomain.com/content/的 GET 请求将以 Http 404 代码（未找到）结束。这个结果很可能不会被缓存，所以我猜这就是它对你不起作用的原因。

更新： 必须满足某些条件才能从缓存提供响应。您应该启用 apache http 客户端的日志记录（例如http://hc.apache.org/httpclient-3.x/logging.html）。您可以调试正在发生的情况以及其他 URL 缓存未命中的原因。您可能还应该下载该库的源代码并查看那里（http://hc.apache.org/downloads.cgi）。尤其是你会对org.apache.http.impl.client.cache.CachedResponseSuitabilityChecker课堂感兴趣。这也应该对您使用该库进行后续开发有所帮助。

顺便提一句。http://muvireviews.com/celebrity/full_view/41/Shahrukh-khan返回此标头：

Cache-Control:no-store, no-cache, must-revalidate, post-check=0, pre-check=0, max-age=0, no-cache, no-store

并且由于 if 语句CachedResponseSuitabilityChecker：

            if (HeaderConstants.CACHE_CONTROL_NO_CACHE.equals(elt.getName())) {
                log.trace("Response contained NO CACHE directive, cache was not suitable");
                return false;
            }

缓存将不会被使用。

祝你好运 ;）