google.com/appengine/docs/java/urlfetch/">URL Fetch.
Implementation is thread-safe. For maximum efficiency, applications should use a single globally-shared instance of the HTTP transport.
URL Fetch is only available on Google App Engine (not on any other Java environment), and is the underlying HTTP transport used for App Engine. Their implementation of {@link HttpURLConnection}is simply an abstraction layer on top of URL Fetch. By implementing a transport that directly uses URL Fetch, we can optimize the behavior slightly, and can potentially take advantage of features in URL Fetch that are not available in {@link HttpURLConnection}. Furthermore, there is currently a serious bug in how HTTP headers are processed in the App Engine implementation of {@link HttpURLConnection}, which we are able to avoid using this implementation. Therefore, this is the recommended transport to use on App Engine.
@since 1.10
@author Yaniv Inbar