SlackApi.java

package net.gpedro.integrations.slack;

import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLEncoder;

import com.google.gson.JsonObject;


public class SlackApi {

	private String service;
	
	public SlackApi(String service) {
		if(service == null) {
			throw new IllegalArgumentException("Missing WebHook URL Configuration @ SlackApi");
		} else if (!service.startsWith("https://hooks.slack.com/services/")) {
			throw new IllegalArgumentException("Invalid Service URL. WebHook URL Format: https://hooks.slack.com/services/{id_1}/{id_2}/{token}");
		}
		
		this.service = service;
	}
	
	public void call(SlackMessage message) {
		if(message != null) {
			this.send(message.prepare());
		}
	}
	
	private String send(JsonObject message) {
		URL url;
	    HttpURLConnection connection = null;  
	    try {
	      //Create connection
	      url = new URL(this.service);
	      connection = (HttpURLConnection)url.openConnection();
	      connection.setRequestMethod("POST");
	      connection.setConnectTimeout(5000);
	      connection.setUseCaches (false);
	      connection.setDoInput(true);
	      connection.setDoOutput(true);

	      String payload = "payload="+URLEncoder.encode(message.toString(), "UTF-8");
	      
	      //Send request
	      DataOutputStream wr = new DataOutputStream (
	                  connection.getOutputStream ());
	      wr.writeBytes(payload);
	      wr.flush ();
	      wr.close ();

	      //Get Response	
	      InputStream is = connection.getInputStream();
	      BufferedReader rd = new BufferedReader(new InputStreamReader(is));
	      String line;
	      StringBuffer response = new StringBuffer(); 
	      while((line = rd.readLine()) != null) {
	        response.append(line);
	        response.append('\r');
	      }
	      
	      System.out.println(response.toString());
	      rd.close();
	      return response.toString();

	    } catch (Exception e) {

	      e.printStackTrace();
	      return null;

	    } finally {

	      if(connection != null) {
	        connection.disconnect(); 
	      }
	    }
	}
	
}