rename applicationContext to httpContext (Yaniv didn't like applicationContext name in http artifact)

Author: peleyal

google-http-client/src/main/java/com/google/api/client/http/ApplicationContext.java renamed to google-http-client/src/main/java/com/google/api/client/http/HttpContext.java

@@ -17,15 +17,21 @@
 import com.google.api.client.json.JsonFactory;
 
 /**
- * @author [email protected] (Your Name Here)
+ * HTTP context which contains the transport layer, the Json factory and the user agent header which
+ * are going to be used in the different requests.
  *
+ * @author [email protected] (Nick Miceli)
+ * @author [email protected] (Eyal Peled)
+ * @since 1.18
  */
-public interface ApplicationContext {
+public interface HttpContext {
 
+  /** Returns the transport layer. */
   HttpTransport getTransport();
 
+  /** Returns the Json factory. */
   JsonFactory getJsonFactory();
 
-  String getApplicationName();
-
+  /** Returns the user-agent header which is going to be used in every HTTP request. */
+  String getUserAgent();
 }

google-http-client/src/main/java/com/google/api/client/http/apache/ApacheHttpTransport.java

@@ -87,6 +87,24 @@ public final class ApacheHttpTransport extends HttpTransport {
   /** Apache HTTP client. */
   private final HttpClient httpClient;
 
+  /**
+   * {@link Beta} <br/>
+   * Returns a global thread-safe instance.
+   *
+   * @since 1.18
+   */
+  @Beta
+  public static ApacheHttpTransport getDefaultInstance() {
+    return InstanceHolder.INSTANCE;
+  }
+
+  /** Holder for the result of {@link #getDefaultInstance()}. */
+  @Beta
+  static class InstanceHolder {
+    static final ApacheHttpTransport INSTANCE = new ApacheHttpTransport();
+  }
+
+
   /**
    * Constructor that uses {@link #newDefaultHttpClient()} for the Apache HTTP client.
    *