Adding support for Proxy in Slack / SlackService

Requirement for ashwanthkumar/gocd-slack-build-notifier#2

Author: ashwanthkumar

src/main/java/in/ashwanthkumar/slack/webhook/Slack.java

@@ -4,6 +4,8 @@
 import in.ashwanthkumar.utils.collections.Lists;
 
 import java.io.IOException;
+import java.net.InetSocketAddress;
+import java.net.Proxy;
 import java.util.List;
 
 import static in.ashwanthkumar.utils.lang.StringUtils.isEmpty;
@@ -17,13 +19,22 @@ public class Slack {
     private String channel;
     private String user;
     private String icon;
-    private SlackService slackService = new SlackService();
+    private SlackService slackService;
 
-    public Slack(String webhookUrl) {
+    public Slack(String webhookUrl, Proxy proxy) {
         if (isEmpty(webhookUrl)) {
             throw new IllegalArgumentException("Webhook url is not provided");
         }
         this.webhookUrl = webhookUrl;
+        this.slackService = new SlackService(proxy);
+    }
+
+    public Slack(String webhookUrl) {
+        this(webhookUrl, (Proxy) null);
+    }
+
+    public Slack(String webhookUrl, String hostname, int port) {
+        this(webhookUrl, new Proxy(Proxy.Type.HTTP, new InetSocketAddress(hostname, port)));
     }
 
     /**

src/main/java/in/ashwanthkumar/slack/webhook/service/SlackService.java

@@ -2,7 +2,6 @@
 
 import com.google.api.client.http.GenericUrl;
 import com.google.api.client.http.HttpRequestFactory;
-import com.google.api.client.http.HttpTransport;
 import com.google.api.client.http.UrlEncodedContent;
 import com.google.api.client.http.javanet.NetHttpTransport;
 import com.google.api.client.util.Maps;
@@ -11,6 +10,7 @@
 import in.ashwanthkumar.slack.webhook.SlackMessage;
 
 import java.io.IOException;
+import java.net.Proxy;
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
@@ -21,8 +21,17 @@
 
 
 public class SlackService {
-    private final HttpTransport HTTP_TRANSPORT = new NetHttpTransport();
-    private final HttpRequestFactory requestFactory = HTTP_TRANSPORT.createRequestFactory();
+    private final HttpRequestFactory requestFactory;
+
+    public SlackService(Proxy proxy) {
+        NetHttpTransport.Builder builder = new NetHttpTransport.Builder();
+        builder.setProxy(proxy);
+        requestFactory = builder.build().createRequestFactory();
+    }
+
+    public SlackService() {
+        this(null);
+    }
 
     public void push(String webHookUrl, SlackMessage text, String username, String imageOrIcon, String destination, List<SlackAttachment> attachments) throws IOException {
         Map<String, Object> payload = new HashMap<String, Object>();