/**
* Performs the web-service call. If the <code>session</code> parameter is <code>non-null</code>
* then an authenticated call is made. If it's <code>null</code> then an unauthenticated call is
* made.<br>
* The <code>apiKey</code> parameter is always required, even when a valid session is passed to
* this method.
*
* @param method The method to call
* @param apiKey A Last.fm API key
* @param params Parameters
* @param session A Session instance or <code>null</code>
* @return the result of the operation
*/
private Result call(String method, String apiKey, Map<String, String> params) {
params =
new HashMap<String, String>(params); // create new Map in case params is an immutable Map
InputStream inputStream = null;
// try to load from cache
String cacheEntryName = Cache.createCacheEntryName(method, params);
if (cache != null) {
inputStream = getStreamFromCache(cacheEntryName);
}
// no entry in cache, load from web
if (inputStream == null) {
// fill parameter map with apiKey and session info
params.put(PARAM_API_KEY, apiKey);
try {
HttpURLConnection urlConnection = openPostConnection(method, params);
inputStream = getInputStreamFromConnection(urlConnection);
if (inputStream == null) {
this.lastResult =
Result.createHttpErrorResult(
urlConnection.getResponseCode(), urlConnection.getResponseMessage());
return lastResult;
} else {
if (cache != null) {
long expires = urlConnection.getHeaderFieldDate("Expires", -1);
if (expires == -1) {
expires = cache.findExpirationDate(method, params);
}
if (expires != -1) {
cache.store(
cacheEntryName, inputStream, expires); // if data wasn't cached store new result
inputStream = cache.load(cacheEntryName);
if (inputStream == null) throw new CallException("Caching/Reloading failed");
}
}
}
} catch (IOException e) {
throw new CallException(e);
}
}
try {
Result result = createResultFromInputStream(inputStream);
if (!result.isSuccessful()) {
Log.w(TAG, String.format("API call failed with result: %s%n", result));
if (cache != null) {
cache.remove(cacheEntryName);
}
}
this.lastResult = result;
return result;
} catch (IOException e) {
throw new CallException(e);
} catch (SAXException e) {
throw new CallException(e);
}
}
