Tomcat erecting a simple websocket server

Environment:
JDK 8
Eclipse-oxygen
Tomcat 7.088

1. Build a Maven project in eclipse
   
   
   Click Next
   
   Like, pick that Maven-archetype-webapp, click Next.
   
   Write your name at the group ID and artifact ID, and start your own, click Finish
   
   This will be built, leave the error first.
   Open Pom.xml, go to Riga content
   
   Join:

   <dependency>   <groupId>javax.websocket</groupId>   <artifactId>javax.websocket-api</artifactId>   <version>1.0</version>     <scope>provided</scope></dependency>

   Again to solve the problem of error
   Start with a new folder,libs under your project
   
   Find your Tomcat directory/lib/
   
   Put the two jar pack in the box: Serverlet-api.jar Websocket-api.jar to the Libs folder you just built.
   
   And then put the two jar package add to Build Path
   
   This will not be an error, that is to say WebSocket server development ready OK.

Let's start writing the service.

With annotation injection, a script is ok

Package Com.r.server;import Java.io.ioexception;import Java.util.concurrent.concurrenthashmap;import  javax.websocket.*; Import Javax.websocket.server.ServerEndpoint; @ServerEndpoint ("/ws") public class WSServer {///static variable, used to record the current number of online connections.      It should be designed to be thread-safe.      private static int onlinecount = 0;    private static concurrenthashmap<session, wsserver> ssmap= new concurrenthashmap<session, wsserver> ();      A connection session with a client, which is required to send data to the client private session session; /** * Connection established method of successful call * @param session optional parameters. Session is a connection to a client, it needs to send data to the client */@OnOpen public void OnOpen (session session) {this.session =          Session        Ssmap.put (session, this);           Addonlinecount (); Online number plus 1 System.out.println ("New connection added!")      The current number of online people is "+ getonlinecount ());        }/** * method to close the call */@OnClose public void OnClose () {ssmap.remove (this.session);           Subonlinecount (); Online number minus 1 System.out.println ("There is a connectionShut down!      The current number of online people is "+ getonlinecount ());      /** * The method that is called after receiving the client message * @param message sent by the client * @param session Optional Parameters */@OnMessage          public void OnMessage (String message, session session) {SYSTEM.OUT.PRINTLN ("Message from client:" + message);        WSServer tmp = Ssmap.get (session);        try {tmp.sendmessage (message);        } catch (IOException E1) {e1.printstacktrace (); }}/** * Called when an error occurred * @param session * @param error */@OnError public void OnError (Se          Ssion session, throwable error) {System.out.println ("error occurred");      Error.printstacktrace (); }/** * This method is not the same as the above methods.      Without annotations, it is based on the method you need to add.          * @param message * @throws IOException */public void SendMessage (String message) throws ioexception{          This.session.getBasicRemote (). SendText (message);      This.session.getAsyncRemote (). SendText (message); } public static synchronizedint Getonlinecount () {return onlinecount;      } public static synchronized void Addonlinecount () {wsserver.onlinecount++;      } public static synchronized void Subonlinecount () {wsserver.onlinecount--; }}

This code is also copied from the Internet, but after my modification

@ServerEndpoint("/ws")

This line of code indicates that the address of this websockt server is when the project is running on the Tomcat server:
Ws://localhost:8080/web2/ws, where Web2 is the Artifect Id of the previous project, this example is WEB2
Each session here is a connection to each client.
Ssmap is a thread-safe map that joins clients to this map whenever a client connects
The original OnMessage method, is to receive the message after the message sent to all clients, a little chat room meaning, I changed it, who sent the message to send back to WHO

Then modify the index.jsp (this is the test)

<%@ page contenttype= "Text/html;charset=utf-8"%> 

Finally add the project to Tomcat and run Tomcat (operating in Eclipse)

Then open the browser, 360 Ah, Firefox, Chrome, whatever, enter the path to this project
Http://localhost:8080/web2
This will open index.jsp
Open post page Auto Connect websocket service

Sends a message that the server receives and returns to the client

Click Close WebSocket Connection will disconnect


These operations are also shown on the Tomcat server


This is the simple server-side and test JSP page

Tomcat erecting a simple websocket server