How to Add Chat Functionality to a Maven Java Web App

Today we learn how to add chat functionality to a java web application. We do this by using a java library based on CometD chat libraries. This is a 2 part tutorial.

This is Part 1 of a 2-part blog post

Requirements. To be able to follow this tutorial, you should understand:

• The basics of building a java web application with Servlets.
• How to use [Java Server Pages (JSP)](https://docs.oracle.com/javaee/5/tutorial/doc/bnagy/“>Java Server Pages (JSP))
• How to use Maven
• How to use Github

First we ask: Why add chat functionality?

Each visitor to a website could be engaged at the critical window when they are about to make a decision. It could also be at the time algorithm decides they are confused about something (e.g visiting the same link, back and forth 3 times). At that point a chat window could appear with a customer care representative at the other end to engage the potential custeomer. With that in mind, the following are basically the advantages of chat:

• Reduce expenses.
• Increase sales.
• Improve customer service and loyalty.
• Discover customer pain points.
• Faster problem resolution.
• Customer convenience.
• Competitive advantages.
• Expand market reach.

So what is CometD?

| The CometD libraries allow your application to send messages in three forms: Push-Subscribe, Peer-to-Peer and Remote-Call.

• With Publish-Subscribe, a message sent by a publisher is broadcast to many subscribers.

This is the typical case for chat rooms, for example.

• With Peer-to-Peer, a message is sent by a sender to a specific receiver. This is the

typical case for private one-to-one chats, for example.

• With Remote-Call, a “message” is sent by a client to the server to perform a specific

action. This is the typical case for creating a new chat room, for example.

Learn more about the CometD messaging features in the CometD reference manual.

Now how do we add CometD chat functionality to a java web application?

To add CometD chat functionality to a java web application, we will be using the CometD chat library I wrote. Clone the library from github. Then follow the next steps.

####Step 1#### Open your favorite java ide and create a maven web java application.

####Step 2#### Add the CometdD chat library you cloned from github as a dependency to your maven java web application.

####Step 3#### Add the xml below to your web.xml

  <!-- Servlet to query cometd chat messages -->
  <servlet>
      <servlet-name>messages</servlet-name>
      <servlet-class>com.looseboxes.cometd.chat.servlets.Messages</servlet-class>
      <async-supported>true</async-supported>
  </servlet>
  <servlet-mapping>
      <servlet-name>messages</servlet-name>
      <url-pattern>/chat/messages</url-pattern>
  </servlet-mapping>
  <!-- CometdChat WebApp Config -->
  <context-param>
      <param-name>cometdChatAppName</param-name>
      <param-value>[PUT A NAME HERE]</param-value>
  </context-param>
  <filter>
      <filter-name>continuation</filter-name>
      <filter-class>org.eclipse.jetty.continuation.ContinuationFilter</filter-class>
      <async-supported>true</async-supported>
  </filter>
  <filter-mapping>
      <filter-name>continuation</filter-name>
      <url-pattern>/cometd/*</url-pattern>
  </filter-mapping>
  <!-- Cometd Servlet -->
  <servlet>
      <servlet-name>cometd</servlet-name>
      <servlet-class>com.looseboxes.cometd.chat.servlets.CometdWithMessageConsumer</servlet-class>
      <async-supported>true</async-supported>
      <init-param>
          <param-name>transports</param-name>
          <param-value>org.cometd.websocket.server.WebSocketTransport</param-value>
      </init-param>
      <init-param>
          <param-name>services</param-name>
          <param-value>com.looseboxes.cometd.chat.ChatService</param-value>
      </init-param>
      <load-on-startup>1</load-on-startup>
  </servlet>
  <servlet-mapping>
      <servlet-name>cometd</servlet-name>
      <url-pattern>/cometd/*</url-pattern>
  </servlet-mapping>

####Step4#### Add the code below to any ServletContextListener.

public void contextInitialized(ServletContextEvent servletContextEvent) {
    final ServletContext servletContext = servletContextEvent.getServletContext();
    final CometdChat cometdChat = new CometdChat(servletContext);
}

####Step 5#### Add the code below to the head section of any jsp or jspf etc, page you want chat to be available from.

<%@taglib uri="/META-INF/tlds/cometdchat" prefix="cometdchat"%>
<cometdchat:joinChat loginUserDisplayName="me" windowBackground="navy"/>

####Hurray! We made it####

Now when you open the page where you added the above taglib, a small chat window should open.

In Part 2 we will delve a bit deeper into whats happening behind the scenes

References:

• CometD Messaging.
• Top 10 Live Chat Benefits.