Core HTTP components based on the blocking I/O model. These deal with the fundamental things required for using the HTTP protocol, such as representing a {@link org.apache.http.HttpMessage message} including it's {@link org.apache.http.Header headers} and optional {@link org.apache.http.HttpEntity entity}, and {@link org.apache.http.HttpConnection connections} over which messages are sent. In order to prepare messages before sending or after receiving, there are interceptors for {@link org.apache.http.HttpRequestInterceptor requests} and {@link org.apache.http.HttpResponseInterceptor responses}.