Connecting to the Cloud in Java

Connecting to the Cloud in Java


Connecting to the Cloud in Java

·         Overview

·         Prerequisites

Import Java Client Project

·         Set Java Client Variables

Using Java Client Application

·         Starting Cloud Connection

·         Subscribe to Data

·         Publish Data

·         Receive Subscription




Connecting to the Cloud in Java



In this example, we will use Eclipse to create a stand-alone MQTT client in Java that implements Everyware™ Cloud Communication Data Model.  The client will simulate an actual device, publishing data to the platform using the MQTT transport protocol, and subscribing to certain topics.  This will give us a test framework to more readily test all aspects of data transfer throughout the Everyware Cloud.


In this section you will learn how to:

  • Import the sample Java Client project into Eclipse
  • Publish data to the cloud
  • Subscribe to a topic namespace in the cloud




The Everyware Cloud example code is available on the GitHub repository at  Make sure before continuing with this example that you have set up your Eclipse workspace, installed Maven, and downloaded the example code (see Setting up Eclipse Environment for Java). 




Import Java Client Project


In Eclipse, select File | Import.  Select “General | Existing Projects into Workspace,” then click Next.  Click Browse for the root directory, and browse to the workspace location of the cloud examples that were downloaded and installed previously.  Select the “edc-java-client” project folder, but do not enable the checkbox “Copy projects into workspace” (the projects are already in the workspace location).  (If you wish, you may import all the projects, but this tutorial only discusses the EDC Java client.)  You may add the projects to a working set if desired.  Then click Finish.





You should now have the “edc-java-client” project in your workspace, and it should not show any build errors.




NOTE: If you delete the project out of the workspace later, you should not “Delete project contents on disk.”  This is because we have used the Maven install procedures to setup the projects directly into your Eclipse workspace location.  If you do delete the contents on disk, you would need to create a new workspace and re-download the source code from Eurotech’s software repository, as described in Setting up Eclipse Environment for Java.




Set Java Client Variables

Toward the top of the code example, there are several variables noted with comments, which are specific to your Cloud user account.  These variables need to be modified according to your Cloud account credentials, so the Java client can connect properly.  See the section Accessing your Cloud Account to set up an account in Everyware Cloud.


In the sample code, set the following variables with the proper settings of your Cloud broker account, and save changes:



    // >>>>>> Set these variables according to your Cloud user account


       private static final String ACCOUNT_NAME = "myEdcAccount";                        // Your Account name in Cloud

       private static final String ASSET_ID = "my-Device";                               // Unique Asset ID of this client device

       private static final String BROKER_URL = "mqtt://";       // URL address of broker

       private static final String CLIENT_ID = "my-Device-client";                       // Unique Client ID of this client device

       private static final String USERNAME = "myEdcUserName_broker";                    // Username in account, to use for publishing

       private static final String PASSWORD = "myEdcPassword3#";                         // Password associated with Username


    // <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<





Using Java Client Application

The following sections describe the Java Client application and give portions of the relevant code.  See the full Java source code for more details on the program operation.



Starting Cloud Connection

After the client variables have been modified, make a connection to the Cloud by selecting the Run menu, and the option “Run” or “Run as...Java Application”.  You can also select the green Run button  in the Launch toolbar.


This Java code example starts in the main() method by creating an instance of the EDCConfiguration and sets up its identity as a device which will be connecting to the Everyware Cloud.  Then it starts a session, which makes an IP connection to the cloud.



        EdcConfigurationFactory confFact = EdcConfigurationFactory.getInstance();

        EdcConfiguration conf = confFact.newEdcConfiguration(ACCOUNT_NAME, ASSET_ID, BROKER_URL, CLIENT_ID, USERNAME, PASSWORD);

        EdcDeviceProfileFactory profFactory = EdcDeviceProfileFactory.getInstance();

        EdcDeviceProfile prof = profFactory.newEdcDeviceProfile();

        prof.setDisplayName("MyDisplayName");                 // friendly name for this CLIENT_ID, for display in the Cloud

        prof.setModelName("Eclipse Java Client");




The EdcClientFactory is instantiated, using this Java client as a callback.



        EdcCloudClient edcCloudClient = null;

        edcCloudClient = EdcClientFactory.newInstance(conf, prof, new EdcJavaClient());




If you have the proper credentials and have entered them correctly in the code, you should see the debug statements in the Java Console that indicate you have made a successful connection and are publishing and receiving subscribed data. 


13:09:29,318 [main] INFO  EdcCloudClientImpl:79  - # ------------------------------------------------------------

13:09:29,333 [main] INFO  EdcCloudClientImpl:80  - #     Eurotech Everyware Cloud Client

13:09:29,333 [main] INFO  EdcCloudClientImpl:81  - #     Version: 3.0.3

13:09:29,333 [main] INFO  EdcCloudClientImpl:82  - #     Build Version: d4a2723a52796be508906a1a12d7a48707ff6506

13:09:29,333 [main] INFO  EdcCloudClientImpl:83  - #     Build Number: sbx-73

13:09:29,333 [main] INFO  EdcCloudClientImpl:84  - # ------------------------------------------------------------

13:09:29,333 [main] INFO  EdcCloudClientImpl:156  - # ------------------------------------------------------------

13:09:29,333 [main] INFO  EdcCloudClientImpl:157  - #  Connection Properties

13:09:29,333 [main] INFO  EdcCloudClientImpl:158  - #  broker    = mqtt://

13:09:29,333 [main] INFO  EdcCloudClientImpl:159  - #  clientId  = my-Device-client

13:09:29,333 [main] INFO  EdcCloudClientImpl:160  - #  account   = myEdcAccount

13:09:29,333 [main] INFO  EdcCloudClientImpl:161  - #  username  = myEdcUserName_broker

13:09:29,333 [main] INFO  EdcCloudClientImpl:162  - #  password  = XXXXXXXXXXXXXX

13:09:29,333 [main] INFO  EdcCloudClientImpl:163  - #  keepAlive = 30

13:09:29,333 [main] INFO  EdcCloudClientImpl:164  - #

13:09:29,333 [main] INFO  EdcCloudClientImpl:165  - #  Connecting...

13:09:29,645 [main] INFO  EdcCloudClientImpl:188  - #  Connected.

13:09:29,645 [main] INFO  EdcCloudClientImpl:189  - #  Publishing birth certificate on $EDC/myEdcAccount/my-Device-client/MQTT/BIRTH...

13:09:29,676 [main] INFO  EdcCloudClientImpl:204  - #  Completed.

13:09:29,676 [main] INFO  EdcCloudClientImpl:205  - # ------------------------------------------------------------

Session started


If not configured correctly, there will be an error in the console.




Subscribe to Data

Next, the application issues a few subscription requests to the cloud (for data topics, and control topics such as birth certificates), so that we can receive back a copy of the messages that we will later publish.  See Introduction to MQTT Protocol for more information on subscription topics.



        edcCloudClient.subscribe("#", 1);

        edcCloudClient.controlSubscribe("+", "#", 1);




Because the application has subscribed to the topic “#”, you automatically receive back all messages that your client (or any other client on this account) publishes to the Cloud.


Subscribe to data topics of all assets in the account

13:09:29,676 [main] INFO  EdcCloudClientImpl:404  - [my-Device-client] Subscribing on topic: myEdcAccount/my-Device/#, QoS: 1

Subscribe to control topics of all assets in the account

13:09:29,676 [main] INFO  EdcCloudClientImpl:404  - [my-Device-client] Subscribing on topic: $EDC/myEdcAccount/+/#, QoS: 1

Subscribe message ID: 2 confirmed

Subscribe message ID: 3 confirmed




Publish Data

Then a series of messages is published by the application.  The createPayload() method creates an edcPayload() object and populates it with various sample metrics of different data types, including an incrementing counter value (Metric: “counter”) and a GPS position that varies randomly.



            edcCloudClient.publish(pubTSemanticTopic, createPayload(i), 1, false);   //call createPayload() each time



publish on data semantic topic: sample/data

13:37:32,905 [main] INFO  EdcCloudClientImpl:255  - [my-Device-client] Publishing on topic: myEdcAccount/my-Device/sample/data

13:37:32,905 [main] INFO  EdcCloudClientImpl:258  - [my-Device-client] Publishing message with ID: 4

13:37:33,232 [Thread-1] INFO  EdcCloudClientImpl:495  - [my-Device-client] Message published with ID = 4

Publish message ID: 4 confirmed




Receive Subscription

Because of the subscriptions created earlier, we receive back into our client the same messages that we just published.  The controlArrived() or publishArrived() callbacks display the contents of the messages received as a result of a subscription.



    //display data messages received from broker

    public void publishArrived(String assetId, String topic, EdcPayload msg, int qos, boolean retain) {


        System.out.println("Data publish arrived on semantic topic: " + topic + ", qos: " + qos + ", assetId: " + assetId);


        // Print all the metrics

        for (String name : msg.metricNames()) {

            String content = "";

            if (msg.getMetric(name).getClass().isArray()) {

                //display byte arrays as both hex characters and String

                byte[] contentArray = (byte[]) msg.getMetric(name);

                for (int i = 0; i < contentArray.length; i++) {

                    content = content + Integer.toHexString(0xFF & contentArray[i]) + " ";



                content = content + " (as String: '" + new String(contentArray) + "')";

            } else {

                content = msg.getMetric(name).toString();


            System.out.println(name + ":" + content);





The publishArrived() callback parses through each Metric in the EDC message payload, and displays the contents in the Java console.


13:37:33,529 [Thread-1] INFO  EdcCloudClientImpl:578  - [my-Device-client] Publish arrived on topic "myEdcAccount/my-Device/sample/data"

13:37:33,529 [Thread-1] INFO  EdcCloudClientImpl:606  - [my-Device-client] Publish arrived for device ID: my-Device

Data publish arrived on semantic topic: sample/data, qos: 1, assetId: my-Device

str:this is a string

arr:31 32 33  (as String: '123')









Finally, the application sleeps for several seconds to keep the connection alive and to receive any last subscribed messages that might be received, and then the cloud client session is terminated.









This is the end of this example code.  See the section on Viewing Device Data to verify that the data being published from this Java client is arriving in the Cloud broker.