Not able to cache HttpResponse using cachingHttpClient in java?

Question

I'm trying to cache HTTP responses using cachingHttpClient, but in vain. This is the demo which I put together by refering to this link, 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;
        }
    }

  }

Its a simple program, but I'm unable to figure out where am I going wrong. Your help would be appreciated. Thanks.

Answer 1

The GET request with url http://www.mydomain.com/content/ will end up with Http 404 code (Not found). This result can not be most likely cached, so that is why it does not work for you I guess.

UPDATE: There must be certain conditions met in order to serve the response from cache. You should enable logging of apache http client (e.g. http://hc.apache.org/httpclient-3.x/logging.html). Than you can debug what is going on and why there are cache misses for your other URLs. You should probably download also source code of the library and have a look there (http://hc.apache.org/downloads.cgi). Especially you will be interested in org.apache.http.impl.client.cache.CachedResponseSuitabilityChecker class. This should help you also in your following development with the library.

Btw. http://muvireviews.com/celebrity/full_view/41/Shahrukh-khan return this header:

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

and because of the if statement in CachedResponseSuitabilityChecker:

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

the cache will not be used.

Good luck ;)