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This article mainly shows you "WebSocket how to achieve server message push client", the content is easy to understand, clear, hope to help you solve your doubts, the following let the editor lead you to study and learn "WebSocket how to achieve server message push client" this article.

I. background

The project needs to do a function that the message can be obtained in real time. The daily active volume of the system reaches 10000, and the message generated is several times of the active volume. If you use Http to poll the back-end service, it will make the back-end service collapse under too much pressure, so you need a new technical way to change the "pull" way.

II. Solutions

After a variety of Google, Baidu found that html5's new technology WebSocket can be used to change the existing "pull" message into a "push" mode, greatly reducing the pressure on the server.

III. Concrete realization

The example adopts Spring Boot framework.

Introduce pom dependency

Org.springframework.boot

Spring-boot-starter-websocket

Org.springframework.boot

Spring-boot-starter-undertow

Org.springframework.boot

Spring-boot-starter-web

Org.springframework.boot

Spring-boot-starter-tomcat

WebSocket services can be developed using websocket-api or spring-websocket, and we adopt the annotated development method of websocket-api:

Package com.gridsum.techpub.systemhistory.api.server

Import org.slf4j.Logger

Import org.slf4j.LoggerFactory

Import org.springframework.stereotype.Service

Import javax.websocket.*

Import javax.websocket.server.PathParam

Import javax.websocket.server.ServerEndpoint

Import java.io.IOException

Import java.util.Objects

Import java.util.Set

Import java.util.concurrent.CopyOnWriteArraySet

/ * *

* @ author ouyangrongtao

* @ version 1.0

* @ description WebSocketServer

* @ date 10:16 on 2019-12-23

* * /

@ ServerEndpoint ("/ websocket/ {sid}")

@ Service

Public class WebSocketServer {

Private static final Logger logger = LoggerFactory.getLogger (WebSocketServer.class)

Private ClientInfo clientInfo

/ * *

* store the corresponding ClientInfo object for each client.

* /

Private static final Set WEB_SOCKET_SET = new CopyOnWriteArraySet ()

/ * *

* the method called successfully when the connection is established

*

* @ param session session

* @ param sid client

* /

@ OnOpen

Public void onOpen (Session session, @ PathParam ("sid") String sid) {

/ / join set

This.clientInfo = new ClientInfo (sid, session)

WEB_SOCKET_SET.add (clientInfo)

Logger.info ("start listening with a new window: [{}], the current number of online users is [{}]", sid, WEB_SOCKET_SET.size ())

Try {

This.sendMessage (session, "connected successfully")

} catch (IOException e) {

Logger.error ("websocket IO exception")

}

}

/ * *

* connect the method called by closing the call

* /

@ OnClose

Public void onClose () {

/ / remove from set

WEB_SOCKET_SET.remove (this.clientInfo)

Logger.info ("one connection is closed! the current number of people online is: [{}]", WEB_SOCKET_SET.size ())

}

/ * *

*

Messages sent by * @ param message client

* /

@ OnMessage

Public void onMessage (String message) {

Logger.info ("received message from window [{}]: [{}]", this.clientInfo.getSid (), message)

/ / send a message

For (ClientInfo item: WEB_SOCKET_SET) {

Try {

This.sendMessage (item.getSession (), message)

} catch (IOException ignored) {

}

}

}

/ * *

* called in case of error

* @ param session session

* @ param error error message

* /

@ OnError

Public void onError (Session session, Throwable error) {

Logger.error ("error occurred", error)

}

/ * *

* send a message to sid

* @ param message message

* @ param sid sid

* /

Public void sendMessage (String message, String sid) {

Logger.info ("push message to window [{}], push content: [{}]", sid, message)

ClientInfo client = WEB_SOCKET_SET.parallelStream ()

.filter (item-> item.getSid () .equals (sid)) .findFirst () .orElse (null)

If (client! = null) {

Try {

This.sendMessage (client.getSession (), message)

} catch (IOException ignored) {

}

}

}

/ * *

* implement active push on the server

* @ param session session

* @ param message message

* @ throws IOException IOException

* / which gynecological hospital in Zhengzhou has a good http://www.sptdfk.com/

Private void sendMessage (Session session, String message) throws IOException {

Session.getBasicRemote () sendText (message)

}

Class ClientInfo {

/ * *

* receive sid

* /

Private String sid = ""

/ * *

* client

* /

Private Session session

Public ClientInfo () {}

Private ClientInfo (String sid, Session session) {

This.sid = sid

This.session = session

}

Private String getSid () {

Return sid

}

Private Session getSession () {

Return session

}

@ Override

Public boolean equals (Object o) {

If (this = = o) {

Return true

}

If (o = = null | | getClass ()! = o.getClass ()) {

Return false

}

ClientInfo that = (ClientInfo) o

Return Objects.equals (sid, that.sid)

}

@ Override

Public int hashCode () {

Return Objects.hash (sid)

}

}

}

Front-end code

Run WebSocketClient1000001

Come to an interface that sends messages.

/ * *

* send messages to the client

* @ author ouyangrongtao

* /

@ RestController

Public class WebSocketController {

Private WebSocketServer webSocketServer

@ Autowired

Public WebSocketController (WebSocketServer webSocketServer) {

This.webSocketServer = webSocketServer

}

@ PostMapping ("/ socket/push")

Public boolean pushToWeb (@ RequestBody Map content) {

WebSocketServer.sendMessage (content.get ("message"), content.get ("cid"))

Return true

}

}

So far, it has been basically finished. Using Postman to call the sending interface, it is found that the client can receive the sent message.

IV. Problem record

When doing this, because of the Tomcat container used in the project, there is a conflict between the Tomcat-related package and the WebSocket dependency, and the project cannot be started in the end. The solution is to change the Tomcat container to Undertow.

Org.springframework.boot

Spring-boot-starter-undertow

Org.springframework.boot

Spring-boot-starter-web

Org.springframework.boot

Spring-boot-starter-tomcat

Exception message:

Caused by: java.lang.IllegalStateException: javax.websocket.server.ServerContainer not available

At org.springframework.util.Assert.state (Assert.java:73)

At org.springframework.web.socket.server.standard.ServerEndpointExporter.afterPropertiesSet (ServerEndpointExporter.java:106)

At org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods (AbstractAutowireCapableBeanFactory.java:1753)

At org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean (AbstractAutowireCapableBeanFactory.java:1690)

... 16 common frames omitted

The above is all the contents of the article "how to implement the server message push client in WebSocket". Thank you for reading! I believe we all have a certain understanding, hope to share the content to help you, if you want to learn more knowledge, welcome to follow the industry information channel!

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