Web Socket in Spring Boot

Posted By : Anil Kumar | 26-May-2018

Introduction:

Socket programming or web socket is used for communication between the applications server and client.

Java Socket programming is of two types of connection-oriented or connectionless.

1. Socket and ServerSocket classes are used for connection-oriented socket programming.

Socket class

Important methods

Method:

1) public InputStream getInputStream()

returns the InputStream attached to this socket.

2) public OutputStream getOutputStream()

returns the OutputStream attached to this socket.

3) public synchronized void close()

closes this socket

ServerSocket class:

The ServerSocket class is used to create a server socket.

That socket object is used to establish communication with the clients/users.

Important methods:

1) public Socket accept()

2) public synchronized void close()

closes the server socket.

Example:

Let's go with a simple java socket programme in which users sends a text and server receives that text.

1. Create a web config file

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.context.annotation.Configuration;
import org.springframework.messaging.simp.config.MessageBrokerRegistry;
import org.springframework.web.socket.config.annotation.AbstractWebSocketMessageBrokerConfigurer;
import org.springframework.web.socket.config.annotation.EnableWebSocketMessageBroker;
import org.springframework.web.socket.config.annotation.StompEndpointRegistry;



@Configuration
@EnableWebSocketMessageBroker
public class WebSocketConfig extends AbstractWebSocketMessageBrokerConfigurer {

	private static final Logger LOGGER = LoggerFactory.getLogger(WebSocketConfig.class);

	@Override
	public void configureMessageBroker(MessageBrokerRegistry config) {
		try {
			config.enableSimpleBroker("/topic");
			config.setApplicationDestinationPrefixes("/app");
		}
		catch(Exception e){
			LOGGER.error("unable to send data with socket connection: "+e.getMessage());
		}
	}

	@Override
	public void registerStompEndpoints(StompEndpointRegistry registry) {
		LOGGER.info("registry added");
		try {
			registry.addEndpoint("/socket").setAllowedOrigins("*").withSockJS();
		}
		catch (Exception e){
			LOGGER.error("unable to connect socket connection: "+e.getMessage());
		}
	}
}

2. Create a Web Socket class with @EnableScheduling to auto update the data
and push the data on the client side.

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.ResponseEntity;
import org.springframework.messaging.handler.annotation.MessageMapping;
import org.springframework.messaging.handler.annotation.SendTo;
import org.springframework.scheduling.annotation.EnableScheduling;
import org.springframework.scheduling.annotation.Scheduled;
import org.springframework.stereotype.Component;
import org.springframework.stereotype.Controller;

import com.accounts.mapping.URLMapping;
import com.accounts.service.MarketDataService;



@Controller
@Component
@Configuration
@EnableScheduling
public class WebSocketController {


	@Autowired
	MarketDataService marketDataService;
	
	@Scheduled(fixedDelay=3000)
    @MessageMapping(URLMapping.MARKET_DATA)
    @SendTo("/topic"+ URLMapping.MARKET_DATA)
    public ResponseEntity<Object> fetchMarketData() {
        return marketDataService.fetchMarketData();
    }
}