This libraries is composed of several modules:

google-http-client

Google HTTP Client Library for Java (google-http-client) is designed to be compatible with all supported Java platforms, including Android.

google-http-client-android

Android extensions to the Google HTTP Client Library for Java (google-http-client-android) support Java Google Android (only for SDK >= 2.1) applications. This module depends on google-http-client.

google-http-client-apache-v2

Apache extension to the Google HTTP Client Library for Java (google-http-client-apache-v2) that contains an implementation of HttpTransport based on the Apache HTTP Client. This module depends on google-http-client.

google-http-client-appengine

Google App Engine extensions to the Google HTTP Client Library for Java (google-http-client-appengine) support Java Google App Engine applications. This module depends on google-http-client.

google-http-client-gson

GSON extension to the Google HTTP Client Library for Java (google-http-client-gson) that contains an implementation of JsonFactory based on the GSON API. This module depends on google-http-client.

google-http-client-jackson2

Jackson2 extension to the Google HTTP Client Library for Java (google-http-client-jackson2) that contains an implementation of JsonFactory based on the Jackson2 API. This module depends on google-http-client.

google-http-client-protobuf

Protocol buffer extensions to the Google HTTP Client Library for Java (google-http-client-protobuf) support protobuf data format. This module depends on google-http-client.

google-http-client-xml

XML extensions to the Google HTTP Client Library for Java (google-http-client-xml) support the XML data format. This module depends on google-http-client.