Add header on WebSocket handshake with modifyHandshake

Question

I'm trying to send a custom header during the handshake. I can intercept the handshake with the ServerEndpointConfig.Configurator and override modifyHandshake. ``` public class WebsocketConfigurator extends ServerEndpointConfig.Configurator { public static final String HEADER_SOCKET_ID = "X-Socket-Id"; @Override public void modifyHandshake(ServerEndpointConfig sec, HandshakeRequest request, HandshakeResponse response) { String id = UUID.randomUUID().toString(); List list = new ArrayList(); list.add(id); response.getHeaders().put(HEADER_SOCKET_ID, list); sec.getUserProperties().put(HEADER_SOCKET_ID, id); } } ``` The method gets called and the id gets added to the response headers, though it doesn't send the additional headers. I sniffed it with wireshark to make sure it's not the client framework: ``` GET /websocket HTTP/1.1 Upgrade: websocket Connection: Upgrade Host: localhost:8080 Origin: http://localhost:8080 Pragma: no-cache Cache-Control: no-cache Sec-WebSocket-Ke…

Accepted Answer

I assume it was a bug in Jetty's implementation of Websockets. I was using

```
Jetty: 9.1.1.v20140108
```

I briefly looked into the code and it seemed to me that they called modifyHandshake after the response was sent. Though could be totally wrong too.

However upgrading to

```
 Jetty: 9.2.0.RC0
```

fixes this issue.

```
GET /websocket HTTP/1.1
Upgrade: websocket
Connection: Upgrade
Host: localhost:8080
Origin: http://localhost:8080
Pragma: no-cache
Cache-Control: no-cache
Sec-WebSocket-Key: P93FwyXNrD9ecVHCDywzTg==
Sec-WebSocket-Version: 13
Sec-WebSocket-Extensions: permessage-deflate; client_max_window_bits, x-webkit-deflate-frame
User-Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/36.0.1985.8 Safari/537.36

HTTP/1.1 101 Switching Protocols
Date: Tue, 20 May 2014 10:58:31 GMT
Connection: Upgrade
Sec-WebSocket-Accept: U+tHV5zYWWSX8vDsVdiDo7yUN9s=
Upgrade: WebSocket
X-Socket-Id: f16bc17b-9a5c-45a4-a851-9d66ffb1d2f1
```

Add header on WebSocket handshake with modifyHandshake

Solution

Problem