FireAndIce FireAndIce - 23 days ago 5
Java Question

Not able to cache HttpResponse using cachingHttpClient in java?

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

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 ;)