Enabling Cross Origin Requests for WebSockets in Spring
<p>I have a OpenShift Wildfly server. I am building a website with the <code>Spring MVC</code> framework. One of my webpages also uses a WebSocket connection. On the server side, I have used the <code>@ServerEndpoint</code> annotation and <code>javax.websocket.*</code> library to create my websocket: </p>

<pre><code>package com.myapp.spring.web.controller;
import java.io.IOException;

import javax.websocket.OnClose;
import javax.websocket.OnError;
import javax.websocket.OnMessage;
import javax.websocket.OnOpen;
import javax.websocket.Session;
import javax.websocket.server.ServerEndpoint;

import org.springframework.web.socket.server.standard.SpringConfigurator;


@ServerEndpoint(value="/serverendpoint", configurator = SpringConfigurator.class)

public class serverendpoint {

    @OnOpen
    public void handleOpen () {
        System.out.println("JAVA: Client is now connected...");
    }

    @OnMessage
    public String handleMessage (Session session, String message) throws IOException {

        if (message.equals("ping")) {
//            return "pong"
                session.getBasicRemote().sendText("pong");
        }
        else if (message.equals("close")) {
            handleClose();
            return null;
        }
        System.out.println("JAVA: Received from client: "+ message);
        MyClass mc = new MyClass(message);
        String res = mc.action();
        session.getBasicRemote().sendText(res);
        return res;
    }

    @OnClose
    public void handleClose() {
        System.out.println("JAVA: Client is now disconnected...");
    }

    @OnError
    public void handleError (Throwable t) {
        t.printStackTrace();
    }
}
</code></pre>

<p>OpenShift gives a default URL, so all of my webpages (html files) have the common (canonical) hostname. For the sake of simplicity, I am calling this URL <code>URL A</code> (<strong><code>projectname-domainname.rhclound.com</code></strong>). I created an alias, CNAME, of <code>URL A</code>, which is called <code>URL B</code> (say <strong><code>https://www.mywebsite.tech</code></strong>). <code>URL B</code> is secure, as it has the <code>https</code>.</p>

<p>I am using a JavaScript client to connect to the WebSocket at the path <code>/serverendpoint</code>. The URI I am using in my html webpage file, <code>test.html</code>, is the following: </p>

<pre><code>var wsUri = "wss://" + "projectname-domainname.rhclound.com" + ":8443" + "/serverendpoint";
</code></pre>

<p>When I open up <code>URL A</code> (<strong><code>projectname-domainname.rhclound.com/test</code></strong>), the WebSocket connects and everything works fine. However, when I try to connect to the websocket using <code>URL B</code> (<strong><code>https://mywebsite.tech/test</code></strong>), the JavaScript client immediately connects and disconnects. </p>

<p>Here is the message from the console that I receive:</p>

<p><a href="https://i.stack.imgur.com/Y03zQ.png" rel="noreferrer"><img src="https://i.stack.imgur.com/Y03zQ.png" alt="enter image description here"></a></p>

<p>Here is my JavaScript code that connects to the WebSocket:</p>

<pre><code>/****** BEGIN WEBSOCKET ******/
            var connectedToWebSocket = false;
            var responseMessage = '';
            var webSocket = null;
            function initWS() {
                connectedToWebSocket = false;
                var wsUri = "wss://" + "projectname-domainname.rhcloud.com" + ":8443" + "/serverendpoint";
                webSocket = new WebSocket(wsUri); // Create a new instance of WebSocket using usUri
                webSocket.onopen = function(message) {
                    processOpen(message);
                };
                webSocket.onmessage = function(message) {
                    responseMessage = message.data;
                    if (responseMessage !== "pong") { // Ping-pong messages to keep a persistent connection between server and client
                        processResponse(responseMessage);
                    }
                    return false;
                };
                webSocket.onclose = function(message) {
                    processClose(message);
                };
                webSocket.onerror = function(message) {
                    processError(message);
                };
                console.log("Exiting initWS()");
            }

            initWS(); //Connect to websocket

            function processOpen(message) {
                connectedToWebSocket = true;
                console.log("JS: Server Connected..."+message);
            }

            function sendMessage(toServer) { // Send message to server
                if (toServer != "close") {
                    webSocket.send(toServer);
                } else {
                    webSocket.close();
                }
            }

            function processClose(message) {
                connectedToWebSocket = false;
                console.log("JS: Client disconnected..."+message);
            }

            function processError(message) { 
                userInfo("An error occurred. Please contact for assistance", true, true);
            }
            setInterval(function() {
                if (connectedToWebSocket) {
                    webSocket.send("ping");
                }
            }, 4000); // Send ping-pong message to server
/****** END WEBSOCKET ******/
</code></pre>

<p>After a lot of debugging and trying various things, I concluded that this was problem was occurring because of the Spring Framework. <strong>This is because before I introduced the <code>Spring Framework</code> in my project, <code>URL B</code> could connect to the WebSocket, but after introducing Spring, it cannot.</strong><br>
I read on <a href="http://docs.spring.io/spring-security/site/docs/current/reference/html/websocket.html" rel="noreferrer">spring's website</a> about WebSocket Policy. I came across their <a href="http://docs.spring.io/spring-security/site/docs/current/reference/html/websocket.html#websocket-sameorigin" rel="noreferrer">same origin policy</a> which states that an alias, <code>URL B</code>, cannot connect to the WebSocket because it is not the same origin as <code>URL A</code> is. To solve this problem I <a href="http://docs.spring.io/spring-security/site/docs/current/reference/html/websocket.html#websocket-sameorigin-disable" rel="noreferrer">disabled the same origin policy with WebSockets</a> as said in the documentation, so I added the following code. I thought that doing so would fix my error. Here is what I added:</p>

<pre><code>import org.springframework.context.annotation.Configuration;
import org.springframework.security.config.annotation.web.socket.AbstractSecurityWebSocketMessageBrokerConfigurer;

@Configuration
public class WebSocketSecurityConfig extends AbstractSecurityWebSocketMessageBrokerConfigurer {

    @Override
    protected boolean sameOriginDisabled() {
        return true;
    }

}
</code></pre>

<p>However, this did not fix the problem, so I added the following method to my <code>ApplicationConfig</code> which <code>extends WebMvcConfigurerAdapter</code>: </p>

<pre><code>@Override
public void addCorsMappings(CorsRegistry registry) {
    registry.addMapping("/**").allowedOrigins("https://www.mywebsite.com");
}
</code></pre>

<p>This also didn't work either. Then I tried this:</p>

<pre><code>package com.myapp.spring.security.config;
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.cors.CorsConfiguration;
import org.springframework.web.cors.UrlBasedCorsConfigurationSource;
import org.springframework.web.filter.CorsFilter;

@Configuration
public class MyCorsFilter {

//  @Bean
//  public FilterRegistrationBean corsFilter() {
//      System.out.println("Filchain");
//      UrlBasedCorsConfigurationSource source = new UrlBasedCorsConfigurationSource();
//      CorsConfiguration config = new CorsConfiguration();
//      config.setAllowCredentials(true);
//      config.addAllowedOrigin("https://www.mymt.tech");
//      config.addAllowedHeader("*");
//      config.addAllowedMethod("*");
//      source.registerCorsConfiguration("/**", config);
//      FilterRegistrationBean bean = new FilterRegistrationBean(new CorsFilter(source));
//      bean.setOrder(0);
//      System.out.println("Filchain");
//      return bean;
//  }

     @Bean
     public CorsFilter corsFilter() {
         System.out.println("Filchain");
         UrlBasedCorsConfigurationSource source = new UrlBasedCorsConfigurationSource();
         CorsConfiguration config = new CorsConfiguration();
         config.setAllowCredentials(true); // you USUALLY want this
         config.addAllowedOrigin("*");
         config.addAllowedHeader("*");
         config.addAllowedMethod("*");
         config.addAllowedMethod("*");
         source.registerCorsConfiguration("/**", config);
         System.out.println("Filchain");
         return new CorsFilter(source);
     }

}
</code></pre>

<p>This also did not work. </p>

<p>I even changed the <code>var wsURI</code> in the JS code to the following: 
<code>var wsUri = "wss://" + "www.mywebsite.com" + ":8443" + "/serverendpoint";</code>
Then <code>var wsUri = "wss://" + "mywebsite.com" + ":8443" + "/serverendpoint";</code></p>

<p>When I did this, the Google Chrome gave me an error, saying that the handshake failed. However, when I have this URL, <code>var wsUri = "wss://" + "projectname-domianname.rhcloud.com" + ":8443" + "/serverendpoint";</code>, I did not get the error that the handshake didn't occur, but I get a message that the connection opened and closed immediately (as seen above). </p>

<p>So how can I fix this?</p>