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Chat with Java and Servlets

Ready to implement a chat application using Twilio Programmable Chat Client?

This application allows users to exchange messages through different channels, using the Twilio Programmable Chat API. On this example, we'll show how to use this API capabilities to manage channels and their usages.

Properati built a web and mobile messaging app to help real estate buyers and sellers connect in real time. Learn more here.

Let's get started!

Generate the Token

In order to create a Twilio Programmable Chat client, you will need an access token. This token holds information about your Twilio Account and Chat API keys.

We generate this token by creating a new AccessToken and providing it with an ChatGrant. With the AccessToken at hand, we can use its method ToJWT() to return its string representation.

        
        
        
        
        src/main/java/com/twilio/chat/TwilioTokenCreator.java

        Generate an Access Token

        src/main/java/com/twilio/chat/TwilioTokenCreator.java

        We can generate a token, now we need a way for the chat app to get it.

        Token Generation Controller

        Token Generation Controller

        On our controller we expose the endpoint responsible for providing a valid token. Using the information provided as parameters:

        • device: identifies the device being used.
        • identity: identifies the user itself.

        It uses tokenGenerator.Generate method to get hold of a new token and return it in a JSON format to be used for our client.

              
              
              
              
              src/main/java/com/twilio/chat/TokenServlet.java

              Token Generation Controller

              src/main/java/com/twilio/chat/TokenServlet.java

              Now that we have a route that generates JWT tokens on demand, let's use this route to initialize our Twilio Chat Client.

              Initialize the Chat Client

              Initialize the Programmable Chat Client

              On our client, we fetch a new Token using a POST request to our endpoint.

              With the token we can create a new Twilio.AccessManager, and initialize our Twilio.Chat.Client.

                    
                    
                    
                    
                    src/main/webapp/js/twiliochat.js

                    Initialize the Chat Client

                    src/main/webapp/js/twiliochat.js

                    Now that we've initialized our Chat Client, lets see how we can get a list of channels.

                    Get the Channel List

                    Get the Channel List

                    After initializing the client, we can call its method getPublicChannelDescriptors to retrieve all visible channels. The method returns a promise which we use to show the list of channels retrieved on the UI.

                          
                          
                          
                          
                          src/main/webapp/js/twiliochat.js

                          Get the Channel List

                          src/main/webapp/js/twiliochat.js

                          Next, we need a default channel.

                          Join the General Channel

                          Join the General Channel

                          This application will try to join a channel called "General Channel" when it starts. If the channel doesn't exist, we'll create one with that name. The scope of this example application will show you how to work only with public channels, but the Programmable Chat client allows you to create private channels and handles invitations.

                          Notice we set a unique name for the general channel as we don't want to create a new general channel every time we start the application.

                                
                                
                                
                                
                                src/main/webapp/js/twiliochat.js

                                Join the General Channel

                                src/main/webapp/js/twiliochat.js

                                Now let's listen for some channel events.

                                Listen to Channel Events

                                Listen to Channel Events

                                Next we listen for channel events. In our case, we're setting listeners to the following events:

                                • messageAdded: When another member sends a message to the channel you are connected to.
                                • typingStarted: When another member is typing a message on the channel that you are connected to.
                                • typingEnded: When another member stops typing a message on the channel that you are connected to.
                                • memberJoined: When another member joins the channel that you are connected to.
                                • memberLeft: When another member leaves the channel that you are connected to.

                                We register a different function to handle each particular event.

                                      
                                      
                                      
                                      
                                      src/main/webapp/js/twiliochat.js

                                      Listen to Channel Events

                                      src/main/webapp/js/twiliochat.js

                                      The client emits events as well. Let's see how we can listen to those events as well.

                                      Listen to Client Events

                                      Listen to Client Events

                                      Just like with channels, we can register handlers for events on the Client:

                                      • channelAdded: When a channel becomes visible to the Client.
                                      • channelRemoved: When a channel is no longer visible to the Client.
                                      • tokenExpired: When the supplied token expires.
                                            
                                            
                                            
                                            
                                            src/main/webapp/js/twiliochat.js

                                            Listen to Client Events

                                            src/main/webapp/js/twiliochat.js

                                            We've actually got a real chat app going here, but let's make it more interesting with multiple channels.

                                            Create a Channel

                                            Create a Channel

                                            When a user clicks on the "+ Channel" link we'll show an input text field where it's possible to type the name of the new channel. Creating a channel is as simple as calling createChannel with an object that has the friendlyName key. You can create a channel with more options listed on the Channels section of the Programmable Chat documentation.

                                                  
                                                  
                                                  
                                                  
                                                  src/main/webapp/js/twiliochat.js

                                                  Create a Channel

                                                  src/main/webapp/js/twiliochat.js

                                                  Next, we will see how we can switch between channels.

                                                  Join Other Channels

                                                  Join Other Channels

                                                  When you tap on the name of a channel from the sidebar, that channel is set as the selectedChannel. The selectChannel method takes care of joining to the selected channel and setting up the selectedChannel.

                                                        
                                                        
                                                        
                                                        
                                                        src/main/webapp/js/twiliochat.js

                                                        Join Other Channels

                                                        src/main/webapp/js/twiliochat.js

                                                        At some point your users will want to delete a channel. Let's have a look at how that can be done.

                                                        Delete a Channel

                                                        Delete a Channel

                                                        Deleting a channel is even more simple than creating one. The application lets the user delete the channel they are currently joined to through the "delete current channel" link. The only thing you need to do to actually delete the channel from Twilio, is call the delete method on the channel you are trying to delete. Like other methods on the Channel object, it'll return a promise where you can set the success handler.