Chapter 340. Jetty Websocket Component

Available as of Camel version 2.10

The websocket component provides websocket endpoints for communicating with clients using websocket. The component uses Eclipse Jetty Server which implements the IETF specification (drafts and RFC 6455). It supports the protocols ws:// and wss://. To use wss:// protocol, the SSLContextParameters must be defined.

Version currently supported

Camel 2.18 uses Jetty 9

340.1. URI format

websocket://hostname[:port][/resourceUri][?options]

You can append query options to the URI in the following format, ?option=value&option=value&…​

340.2. Websocket Options

The Jetty Websocket component supports 14 options which are listed below.

NameDescriptionDefaultType

staticResources (consumer)

Set a resource path for static resources (such as .html files etc). The resources can be loaded from classpath, if you prefix with classpath:, otherwise the resources is loaded from file system or from JAR files. For example to load from root classpath use classpath:., or classpath:WEB-INF/static If not configured (eg null) then no static resource is in use.

 

String

host (common)

The hostname. The default value is 0.0.0.0

0.0.0.0

String

port (common)

The port number. The default value is 9292

9292

Integer

sslKeyPassword (security)

The password for the keystore when using SSL.

 

String

sslPassword (security)

The password when using SSL.

 

String

sslKeystore (security)

The path to the keystore.

 

String

enableJmx (advanced)

If this option is true, Jetty JMX support will be enabled for this endpoint. See Jetty JMX support for more details.

false

boolean

minThreads (advanced)

To set a value for minimum number of threads in server thread pool. MaxThreads/minThreads or threadPool fields are required due to switch to Jetty9. The default values for minThreads is 1.

 

Integer

maxThreads (advanced)

To set a value for maximum number of threads in server thread pool. MaxThreads/minThreads or threadPool fields are required due to switch to Jetty9. The default values for maxThreads is 1 2 noCores.

 

Integer

threadPool (advanced)

To use a custom thread pool for the server. MaxThreads/minThreads or threadPool fields are required due to switch to Jetty9.

 

ThreadPool

sslContextParameters (security)

To configure security using SSLContextParameters

 

SSLContextParameters

useGlobalSslContext Parameters (security)

Enable usage of global SSL context parameters.

false

boolean

socketFactory (common)

To configure a map which contains custom WebSocketFactory for sub protocols. The key in the map is the sub protocol. The default key is reserved for the default implementation.

 

Map

resolveProperty Placeholders (advanced)

Whether the component should resolve property placeholders on itself when starting. Only properties which are of String type can use property placeholders.

true

boolean

The Jetty Websocket endpoint is configured using URI syntax:

websocket:host:port/resourceUri

with the following path and query parameters:

340.2.1. Path Parameters (3 parameters):

NameDescriptionDefaultType

host

The hostname. The default value is 0.0.0.0. Setting this option on the component will use the component configured value as default.

0.0.0.0

String

port

The port number. The default value is 9292. Setting this option on the component will use the component configured value as default.

9292

Integer

resourceUri

Required Name of the websocket channel to use

 

String

340.2.2. Query Parameters (18 parameters):

NameDescriptionDefaultType

maxBinaryMessageSize (common)

Can be used to set the size in bytes that the websocket created by the websocketServlet may be accept before closing. (Default is -1 - or unlimited)

-1

Integer

bridgeErrorHandler (consumer)

Allows for bridging the consumer to the Camel routing Error Handler, which mean any exceptions occurred while the consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. By default the consumer will use the org.apache.camel.spi.ExceptionHandler to deal with exceptions, that will be logged at WARN or ERROR level and ignored.

false

boolean

sessionSupport (consumer)

Whether to enable session support which enables HttpSession for each http request.

false

boolean

staticResources (consumer)

Set a resource path for static resources (such as .html files etc). The resources can be loaded from classpath, if you prefix with classpath:, otherwise the resources is loaded from file system or from JAR files. For example to load from root classpath use classpath:., or classpath:WEB-INF/static If not configured (eg null) then no static resource is in use.

 

String

exceptionHandler (consumer)

To let the consumer use a custom ExceptionHandler. Notice if the option bridgeErrorHandler is enabled then this options is not in use. By default the consumer will deal with exceptions, that will be logged at WARN or ERROR level and ignored.

 

ExceptionHandler

exchangePattern (consumer)

Sets the exchange pattern when the consumer creates an exchange.

 

ExchangePattern

sendTimeout (producer)

Timeout in millis when sending to a websocket channel. The default timeout is 30000 (30 seconds).

30000

Integer

sendToAll (producer)

To send to all websocket subscribers. Can be used to configure on endpoint level, instead of having to use the WebsocketConstants.SEND_TO_ALL header on the message.

 

Boolean

bufferSize (advanced)

Set the buffer size of the websocketServlet, which is also the max frame byte size (default 8192)

8192

Integer

maxIdleTime (advanced)

Set the time in ms that the websocket created by the websocketServlet may be idle before closing. (default is 300000)

300000

Integer

maxTextMessageSize (advanced)

Can be used to set the size in characters that the websocket created by the websocketServlet may be accept before closing.

 

Integer

minVersion (advanced)

Can be used to set the minimum protocol version accepted for the websocketServlet. (Default 13 - the RFC6455 version)

13

Integer

synchronous (advanced)

Sets whether synchronous processing should be strictly used, or Camel is allowed to use asynchronous processing (if supported).

false

boolean

allowedOrigins (cors)

The CORS allowed origins. Use to allow all.

 

String

crossOriginFilterOn (cors)

Whether to enable CORS

false

boolean

filterPath (cors)

Context path for filtering CORS

 

String

enableJmx (monitoring)

If this option is true, Jetty JMX support will be enabled for this endpoint. See Jetty JMX support for more details.

false

boolean

sslContextParameters (security)

To configure security using SSLContextParameters

 

SSLContextParameters

 

340.3. Message Headers

The websocket component uses 2 headers to indicate to either send messages back to a single/current client, or to all clients.

WebsocketConstants.SEND_TO_ALLSends the message to all clients which are currently connected. You can use the sendToAll option on the endpoint instead of using this header.

WebsocketConstants.CONNECTION_KEY

Sends the message to the client with the given connection key.

340.4. Usage

In this example we let Camel exposes a websocket server which clients can communicate with. The websocket server uses the default host and port, which would be 0.0.0.0:9292.
The example will send back an echo of the input. To send back a message, we need to send the transformed message to the same endpoint "websocket://echo". This is needed
because by default the messaging is InOnly.

This example is part of an unit test, which you can find here. As a client we use the AHC library which offers support for web socket as well.

Here is another example where webapp resources location have been defined to allow the Jetty Application Server to not only register the WebSocket servlet but also to expose web resources for the browser. Resources should be defined under the webapp directory.

from("activemq:topic:newsTopic")
   .routeId("fromJMStoWebSocket")
   .to("websocket://localhost:8443/newsTopic?sendToAll=true&staticResources=classpath:webapp");

340.5. Setting up SSL for WebSocket Component

340.5.1. Using the JSSE Configuration Utility

As of Camel 2.10, the WebSocket component supports SSL/TLS configuration through the Camel JSSE Configuration Utility.  This utility greatly decreases the amount of component specific code you need to write and is configurable at the endpoint and component levels.  The following examples demonstrate how to use the utility with the Cometd component.

Programmatic configuration of the component

KeyStoreParameters ksp = new KeyStoreParameters();
ksp.setResource("/users/home/server/keystore.jks");
ksp.setPassword("keystorePassword");

KeyManagersParameters kmp = new KeyManagersParameters();
kmp.setKeyStore(ksp);
kmp.setKeyPassword("keyPassword");

TrustManagersParameters tmp = new TrustManagersParameters();
tmp.setKeyStore(ksp);

SSLContextParameters scp = new SSLContextParameters();
scp.setKeyManagers(kmp);
scp.setTrustManagers(tmp);

CometdComponent commetdComponent = getContext().getComponent("cometds", CometdComponent.class);
commetdComponent.setSslContextParameters(scp);

Spring DSL based configuration of endpoint

...
  <camel:sslContextParameters
      id="sslContextParameters">
    <camel:keyManagers
        keyPassword="keyPassword">
      <camel:keyStore
          resource="/users/home/server/keystore.jks"
          password="keystorePassword"/>
    </camel:keyManagers>
    <camel:trustManagers>
      <camel:keyStore
          resource="/users/home/server/keystore.jks"
          password="keystorePassword"/>
    </camel:trustManagers>
  </camel:sslContextParameters>...
...
  <to uri="websocket://127.0.0.1:8443/test?sslContextParameters=#sslContextParameters"/>...

Java DSL based configuration of endpoint

...
    protected RouteBuilder createRouteBuilder() throws Exception {
        return new RouteBuilder() {
            public void configure() {

                String uri = "websocket://127.0.0.1:8443/test?sslContextParameters=#sslContextParameters";

                from(uri)
                     .log(">>> Message received from WebSocket Client : ${body}")
                     .to("mock:client")
                     .loop(10)
                         .setBody().constant(">> Welcome on board!")
                         .to(uri);
...

340.6. See Also

  • Configuring Camel
  • Component
  • Endpoint
  • Getting Started
  • AHC
  • Jetty
  • Twitter Websocket Example demonstrates how to poll a constant feed of twitter searches and publish results in real time using web socket to a web page.