Add facility to customize HttpRequests

src/main/java/com/asana/Client.java

@@ -235,6 +235,15 @@ public static Client basicAuth(String apiKey, HttpTransport httpTransport) {
         return new Client(new BasicAuthDispatcher(apiKey, httpTransport));
     }
 
+    /**
+     * @param apiKey                Basic Auth API key
+     * @param requestInitializer    The request initializer to use for requests
+     * @return Client instance
+     */
+    public static Client basicAuth(String apiKey, HttpRequestInitializer requestInitializer) {
+        return new Client(new BasicAuthDispatcher(apiKey, requestInitializer));
+    }
+
     /**
      * @param accessToken Personal Access Token
      * @return Client instance
@@ -252,6 +261,15 @@ public static Client accessToken(String accessToken, HttpTransport httpTransport
         return new Client(new AccessTokenDispatcher(accessToken, httpTransport));
     }
 
+    /**
+     * @param accessToken   Personal Access Token
+     * @param requestInitializer    The request initializer to use for requests
+     * @return Client instance
+     */
+    public static Client accessToken(String accessToken, HttpRequestInitializer requestInitializer) {
+        return new Client(new AccessTokenDispatcher(accessToken, requestInitializer));
+    }
+
     /**
      * @param app OAuth application instance
      * @return Client instance
@@ -268,4 +286,14 @@ public static Client oauth(OAuthApp app) {
     public static Client oauth(OAuthApp app, HttpTransport httpTransport) {
         return new Client(new OAuthDispatcher(app, httpTransport));
     }
+
+    /**
+     * @param app           OAuth application instance
+     * @param requestInitializer    The request initializer to use for requests
+     * @return Client instance
+     */
+    public static Client oauth(OAuthApp app, HttpRequestInitializer requestInitializer) {
+        return new Client(new OAuthDispatcher(app, requestInitializer));
+    }
+
 }

src/main/java/com/asana/dispatcher/AccessTokenDispatcher.java

@@ -1,9 +1,6 @@
 package com.asana.dispatcher;
 
-import com.google.api.client.http.GenericUrl;
-import com.google.api.client.http.HttpContent;
-import com.google.api.client.http.HttpRequest;
-import com.google.api.client.http.HttpTransport;
+import com.google.api.client.http.*;
 
 import java.io.IOException;
 
@@ -16,6 +13,11 @@ public AccessTokenDispatcher(String accessToken) {
         this.accessToken = accessToken;
     }
 
+    public AccessTokenDispatcher(String accessToken, HttpRequestInitializer requestInitializer) {
+        super(requestInitializer);
+        this.accessToken = accessToken;
+    }
+
     public AccessTokenDispatcher(String accessToken, HttpTransport httpTransport) {
         super(httpTransport);
         this.accessToken = accessToken;

src/main/java/com/asana/dispatcher/BasicAuthDispatcher.java

@@ -1,9 +1,6 @@
 package com.asana.dispatcher;
 
-import com.google.api.client.http.GenericUrl;
-import com.google.api.client.http.HttpContent;
-import com.google.api.client.http.HttpRequest;
-import com.google.api.client.http.HttpTransport;
+import com.google.api.client.http.*;
 
 import java.io.IOException;
 
@@ -15,6 +12,11 @@ public BasicAuthDispatcher(String apiKey) {
         this.apiKey = apiKey;
     }
 
+    public BasicAuthDispatcher(String apiKey, HttpRequestInitializer requestInitializer) {
+        super(requestInitializer);
+        this.apiKey = apiKey;
+    }
+
     public BasicAuthDispatcher(String apiKey, HttpTransport httpTransport) {
         super(httpTransport);
         this.apiKey = apiKey;

src/main/java/com/asana/dispatcher/Dispatcher.java

@@ -1,27 +1,40 @@
 package com.asana.dispatcher;
 
-import com.google.api.client.http.GenericUrl;
-import com.google.api.client.http.HttpContent;
-import com.google.api.client.http.HttpRequest;
-import com.google.api.client.http.HttpTransport;
+import com.google.api.client.http.*;
 import com.google.api.client.http.javanet.NetHttpTransport;
 
 import java.io.IOException;
 
 public abstract class Dispatcher {
     protected HttpTransport httpTransport;
+    protected HttpRequestInitializer httpRequestInitializer;
 
 
     public Dispatcher() {
-        this.httpTransport = new NetHttpTransport();
+        this(new NetHttpTransport());
+    }
+
+    public Dispatcher(HttpRequestInitializer requestInitializer) {
+        this(new NetHttpTransport(), requestInitializer);
     }
 
     public Dispatcher(HttpTransport httpTransport) {
+        this(httpTransport, null);
+    }
+
+    public Dispatcher(HttpTransport httpTransport, HttpRequestInitializer requestInitializer) {
         this.httpTransport = httpTransport;
+        this.httpRequestInitializer = requestInitializer;
     }
 
     public HttpRequest buildRequest(String method, GenericUrl url, HttpContent content) throws IOException {
-        return httpTransport.createRequestFactory().buildRequest(method, url, content);
+        HttpRequestFactory requestFactory;
+        if(httpRequestInitializer == null) {
+            requestFactory = httpTransport.createRequestFactory();
+        } else {
+            requestFactory = httpTransport.createRequestFactory(httpRequestInitializer);
+        }
+        return requestFactory.buildRequest(method, url, content);
     }
 
     public void sleep(long millis) {

src/main/java/com/asana/dispatcher/OAuthDispatcher.java

@@ -1,10 +1,7 @@
 package com.asana.dispatcher;
 
 import com.asana.OAuthApp;
-import com.google.api.client.http.GenericUrl;
-import com.google.api.client.http.HttpContent;
-import com.google.api.client.http.HttpRequest;
-import com.google.api.client.http.HttpTransport;
+import com.google.api.client.http.*;
 
 import java.io.IOException;
 
@@ -16,6 +13,11 @@ public OAuthDispatcher(OAuthApp app) {
         this.app = app;
     }
 
+    public OAuthDispatcher(OAuthApp app, HttpRequestInitializer requestInitializer) {
+        super(requestInitializer);
+        this.app = app;
+    }
+
     public OAuthDispatcher(OAuthApp app, HttpTransport httpTransport) {
         super(httpTransport);
         this.app = app;