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Browser Calls with Java and Spark

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This Spark web application shows how you can use Twilio Client to make browser-to-phone and browser-to-browser calls.

This application powers the support site for the Birchwood Bicycle Polo Co., which sells equipment to those who play "the sport of kings." It has three main features:

  • Unsatisfied customers can submit support tickets with their phone number and their problem.
  • Support agents can call customers' phones from their browser to follow up on support tickets.
  • Customers can also use their browser to speak with support agents live when available.

In this tutorial, we'll point out the key bits of code that make this application work. Check out the project README on GitHub to see how to run the code yourself.

Learn how Zendesk uses Twilio Client to make phone support available in 40+ countries.

Let's get started!

Submit a support ticket

The home page of our app displays a form for customers to submit support tickets. We use Mustache Template Engine to power the page, and this controller to create the ticket.

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      src/main/java/com/twilio/browsercalls/controllers/TicketController.java

      Create a Ticket

      src/main/java/com/twilio/browsercalls/controllers/TicketController.java

      Let's look at the model.

      The Support Ticket Model

      The Support Ticket Model

      A support ticket has just a few fields - a name for the end user, a description of the trouble they're having, and a phone number we can use to call them back.

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          src/main/java/com/twilio/browsercalls/models/Ticket.java

          Support Ticket Model

          src/main/java/com/twilio/browsercalls/models/Ticket.java

          Now we can create a ticket. Next up, let's work on the dashboard for the support agent.

          Make a Dashboard for our Support Agents

          The support dashboard

          When a support agent visits /dashboard, they see all the support tickets which have been submitted.

          Each ticket also has a "Call Customer" button which invokes a JavaScript function we wrote named callCustomer(). That function kicks off a Twilio Client call to the phone number passed as its sole parameter.

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              src/main/resources/templates/dashboard.mustache

              Support Agent's Dashboard

              src/main/resources/templates/dashboard.mustache

              Great, now we have an interface good enough for our support agents. Next up, in order to let our agents make calls to their customers through the browser, we need to provide them a capability token.

              Let's learn how to generate a Capability Token

              Generate a capability token

              We use the Twilio Java helper library to generate and configure our capability tokens. To allow our support agents to call the phone numbers on our tickets, we use an OutgoingClientScope.

              That method requires an identifier for a TwiML Application. Twilio will send a POST request to our backend every time a user makes a Twilio Client call — the TwiML Application tells Twilio which URL to send that request to.

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                  src/main/java/com/twilio/browsercalls/lib/CapabilityTokenGenerator.java

                  Generate a capability token

                  src/main/java/com/twilio/browsercalls/lib/CapabilityTokenGenerator.java

                  Once we are equipped with our Capability Token, the next step is to set up the Twilio Device Client in the browser.

                  Time for some JavaScript!

                  Set up a Twilio Device Client

                  To use the Twilio Device Client in a web browser we use the twilio.js library.

                  We start by retrieving a capability token from the view we defined in the previous step with a POST request through AJAX. Then we enable the Twilio Device Client for this page by passing our token to Twilio.Device.setup().

                  After that the Twilio.Device.ready() callback will let us know when the browser is ready to make and receive calls.

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                      src/main/resources/public/js/browser-calls.js

                      Set up a Twilio Device

                      src/main/resources/public/js/browser-calls.js

                      Now that we have almost everything in place, it's time to see the core of this tutorial. Let's look at how we can let our agents start a call from their browsers.

                      Call a customer's phone from your browser

                      Calling a Customer (browser-to-phone)

                      When our support agents click on the Call Customer button on a support ticket, the function highlighted on the code snippet will initiate the call.

                      We use Twilio.Device.connect() to begin a new outgoing call. Our backend will tell Twilio how to handle this call, so we include a phoneNumber parameter that we'll use on our call view.

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                          src/main/resources/public/js/browser-calls.js

                          Call a Customer

                          src/main/resources/public/js/browser-calls.js

                          Great! Now our agents are able to make calls to their customers. Next up, let's look at how to connect that call to a phone number.

                          Connect the Call to a Phone Number

                          Connect the call to a phone number

                          Whenever one of our users makes a call, Twilio will send a POST request to the URL we set on our TwiML Application - in this case, /call/connect.

                          We use TwiML to respond to the request and tell Twilio how to handle the call. Twilio will pass along the phoneNumber parameter from the previous step in its request, which we will then Dial in our TwiML.

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                              src/main/java/com/twilio/browsercalls/controllers/CallController.java

                              Connect the call to a phone number

                              src/main/java/com/twilio/browsercalls/controllers/CallController.java

                              After our call view responds, Twilio completes the connection between our support agent's browser and the customer's phone. Let's go back to the browser and see how this is handled.

                              Learn how to indicate a live call

                              The call is live

                              We use the Twilio.Device.connect() callback to update some UI elements to notify our users that they are in a call. This function receives a Connection object, which offers some additional details about the call.

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                                  src/main/resources/public/js/browser-calls.js

                                  Indicate a live call

                                  src/main/resources/public/js/browser-calls.js

                                  And that's all for our browser-to-phone example. Next up, we will go even further and show a browser-to-browser example.

                                  Have the customer start a call from their browser

                                  Call a support agent (browser-to-browser)

                                  Support tickets are useful, but sometimes a customer needs help right now. With just a little more work we let customers speak with a support agent live via a browser-to-browser call.

                                  When a customer clicks the Call support button on the home page we again use Twilio.Device.connect() to initiate the call. This time we don't pass any additional parameters — our backend will route this call to our support agent.

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                                      src/main/resources/public/js/browser-calls.js

                                      Call a Support Agent

                                      src/main/resources/public/js/browser-calls.js

                                      Setting up the browser-to-browser call was rather simple right? Now let's look at how our backend will route this call to our support agent.

                                      Connect an Incoming Call from the Customer

                                      Connect the call to the support agent's client

                                      To allow our support agents to accept incoming calls we use an IncomingClientScope when generating their capability token, passing support_agent as the client's name.

                                      When Twilio sends a POST request to our /call/connect endpoint, we can connect the call to our support agent by responding with a <Client> TwiML noun and the support_agent name.

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                                          What does this thing do?

                                          Connect Incoming Calls

                                          What does this thing do?

                                          That's how we prepare everything for accepting incoming calls. Now we should go back in the browser and see how to handle the connection this time.

                                          Answer the call

                                          Answer the call

                                          When our support agent's client receives an incoming call, it will trigger the function we defined on the Twilio.Device.incoming() callback.

                                          The incoming connection will be in a pending state until we invoke its .accept() method, which we do in a function bound to the Answer Call button.

                                          We also set a .accept() callback to update the UI once the call is live.

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                                              src/main/resources/public/js/browser-calls.js

                                              Answer the call

                                              src/main/resources/public/js/browser-calls.js

                                              Great! Now we know how to work on both cases: browser-to-phone and browser-to-browser calls! Next up, we will see what happens when they decide to hang up the call.

                                              Hanging up the Call

                                              Hang up the Call

                                              In order to finish a call we invoke Twilio.Device.disconnectAll(), which we wired to the Hang up button in our UI.

                                              We also pass a callback function to Twilio.Device.disconnect() above, to reset some UI elements.

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                                                  src/main/resources/public/js/browser-calls.js

                                                  Hang up the Call

                                                  src/main/resources/public/js/browser-calls.js

                                                  That's it! Our Spark application now powers browser-to-phone and browser-to-browser calls using Twilio Client.

                                                  Where to Next?

                                                  Where to next?

                                                  If you're a Java developer working with Twilio, you might also enjoy these tutorials:

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                                                  Did this help?

                                                  Thanks for checking this tutorial out! If you have any feedback to share with us please contact us on Twitter, we'd love to hear it.

                                                  Mario Celi Jose Oliveros Agustin Camino Andrew Baker David Prothero Kat King

                                                  Need some help?

                                                  We all do sometimes; code is hard. Get help now from our support team, or lean on the wisdom of the crowd browsing the Twilio tag on Stack Overflow.

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