Chapter 10. Atmosphere Websocket Component

Available as of Camel version 2.14

The atmosphere-websocket: component provides Websocket based endpoints for a servlet communicating with external clients over Websocket (as a servlet accepting websocket connections from external clients).
The component uses the SERVLET component and uses the https://github.com/Atmosphere/atmosphere[Atmosphere] library to support the Websocket transport in various Servlet containers (e..g., Jetty, Tomcat, …​).

Unlike the Websocket component that starts the embedded Jetty server, this component uses the servlet provider of the container.

Maven users will need to add the following dependency to their pom.xml for this component:

<dependency>
    <groupId>org.apache.camel</groupId>
    <artifactId>camel-atmosphere-websocket</artifactId>
    <version>x.x.x</version>
    <!-- use the same version as your Camel core version -->
</dependency>

10.1. Atmosphere-Websocket Options

The Atmosphere Websocket component supports 8 options which are listed below.

NameDescriptionDefaultType

servletName (common)

Default name of servlet to use. The default name is CamelServlet.

 

String

httpRegistry (common)

To use a custom org.apache.camel.component.servlet.HttpRegistry.

 

HttpRegistry

attachmentMultipart Binding (common)

Whether to automatic bind multipart/form-data as attachments on the Camel Exchange. The options attachmentMultipartBinding=true and disableStreamCache=false cannot work together. Remove disableStreamCache to use AttachmentMultipartBinding. This is turn off by default as this may require servlet specific configuration to enable this when using Servlet’s.

false

boolean

httpBinding (advanced)

To use a custom HttpBinding to control the mapping between Camel message and HttpClient.

 

HttpBinding

httpConfiguration (advanced)

To use the shared HttpConfiguration as base configuration.

 

HttpConfiguration

allowJavaSerialized Object (advanced)

Whether to allow java serialization when a request uses context-type=application/x-java-serialized-object. This is by default turned off. If you enable this then be aware that Java will deserialize the incoming data from the request to Java and that can be a potential security risk.

false

boolean

headerFilterStrategy (filter)

To use a custom org.apache.camel.spi.HeaderFilterStrategy to filter header to and from Camel message.

 

HeaderFilterStrategy

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 Atmosphere Websocket endpoint is configured using URI syntax:

atmosphere-websocket:servicePath

with the following path and query parameters:

10.1.1. Path Parameters (1 parameters):

NameDescriptionDefaultType

servicePath

Required Name of websocket endpoint

 

String

10.1.2. Query Parameters (37 parameters):

NameDescriptionDefaultType

chunked (common)

If this option is false the Servlet will disable the HTTP streaming and set the content-length header on the response

true

boolean

disableStreamCache (common)

Determines whether or not the raw input stream from Servlet is cached or not (Camel will read the stream into a in memory/overflow to file, Stream caching) cache. By default Camel will cache the Servlet input stream to support reading it multiple times to ensure it Camel can retrieve all data from the stream. However you can set this option to true when you for example need to access the raw stream, such as streaming it directly to a file or other persistent store. DefaultHttpBinding will copy the request input stream into a stream cache and put it into message body if this option is false to support reading the stream multiple times. If you use Servlet to bridge/proxy an endpoint then consider enabling this option to improve performance, in case you do not need to read the message payload multiple times. The http/http4 producer will by default cache the response body stream. If setting this option to true, then the producers will not cache the response body stream but use the response stream as-is as the message body.

false

boolean

headerFilterStrategy (common)

To use a custom HeaderFilterStrategy to filter header to and from Camel message.

 

HeaderFilterStrategy

sendToAll (common)

Whether to send to all (broadcast) or send to a single receiver.

false

boolean

transferException (common)

If enabled and an Exchange failed processing on the consumer side, and if the caused Exception was send back serialized in the response as a application/x-java-serialized-object content type. On the producer side the exception will be deserialized and thrown as is, instead of the HttpOperationFailedException. The caused exception is required to be serialized. This is by default turned off. If you enable this then be aware that Java will deserialize the incoming data from the request to Java and that can be a potential security risk.

false

boolean

useStreaming (common)

To enable streaming to send data as multiple text fragments.

false

boolean

httpBinding (common)

To use a custom HttpBinding to control the mapping between Camel message and HttpClient.

 

HttpBinding

async (consumer)

Configure the consumer to work in async mode

false

boolean

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

httpMethodRestrict (consumer)

Used to only allow consuming if the HttpMethod matches, such as GET/POST/PUT etc. Multiple methods can be specified separated by comma.

 

String

matchOnUriPrefix (consumer)

Whether or not the consumer should try to find a target consumer by matching the URI prefix if no exact match is found.

false

boolean

responseBufferSize (consumer)

To use a custom buffer size on the javax.servlet.ServletResponse.

 

Integer

servletName (consumer)

Name of the servlet to use

CamelServlet

String

attachmentMultipartBinding (consumer)

Whether to automatic bind multipart/form-data as attachments on the Camel Exchange. The options attachmentMultipartBinding=true and disableStreamCache=false cannot work together. Remove disableStreamCache to use AttachmentMultipartBinding. This is turn off by default as this may require servlet specific configuration to enable this when using Servlet’s.

false

boolean

eagerCheckContentAvailable (consumer)

Whether to eager check whether the HTTP requests has content if the content-length header is 0 or not present. This can be turned on in case HTTP clients do not send streamed data.

false

boolean

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

optionsEnabled (consumer)

Specifies whether to enable HTTP OPTIONS for this Servlet consumer. By default OPTIONS is turned off.

false

boolean

traceEnabled (consumer)

Specifies whether to enable HTTP TRACE for this Servlet consumer. By default TRACE is turned off.

false

boolean

bridgeEndpoint (producer)

If the option is true, HttpProducer will ignore the Exchange.HTTP_URI header, and use the endpoint’s URI for request. You may also set the option throwExceptionOnFailure to be false to let the HttpProducer send all the fault response back.

false

boolean

connectionClose (producer)

Specifies whether a Connection Close header must be added to HTTP Request. By default connectionClose is false.

false

boolean

copyHeaders (producer)

If this option is true then IN exchange headers will be copied to OUT exchange headers according to copy strategy. Setting this to false, allows to only include the headers from the HTTP response (not propagating IN headers).

true

boolean

httpMethod (producer)

Configure the HTTP method to use. The HttpMethod header cannot override this option if set.

 

HttpMethods

ignoreResponseBody (producer)

If this option is true, The http producer won’t read response body and cache the input stream

false

boolean

preserveHostHeader (producer)

If the option is true, HttpProducer will set the Host header to the value contained in the current exchange Host header, useful in reverse proxy applications where you want the Host header received by the downstream server to reflect the URL called by the upstream client, this allows applications which use the Host header to generate accurate URL’s for a proxied service

false

boolean

throwExceptionOnFailure (producer)

Option to disable throwing the HttpOperationFailedException in case of failed responses from the remote server. This allows you to get all responses regardless of the HTTP status code.

true

boolean

cookieHandler (producer)

Configure a cookie handler to maintain a HTTP session

 

CookieHandler

okStatusCodeRange (producer)

The status codes which are considered a success response. The values are inclusive. Multiple ranges can be defined, separated by comma, e.g. 200-204,209,301-304. Each range must be a single number or from-to with the dash included.

200-299

String

urlRewrite (producer)

Deprecated Refers to a custom org.apache.camel.component.http.UrlRewrite which allows you to rewrite urls when you bridge/proxy endpoints. See more details at http://camel.apache.org/urlrewrite.html

 

UrlRewrite

mapHttpMessageBody (advanced)

If this option is true then IN exchange Body of the exchange will be mapped to HTTP body. Setting this to false will avoid the HTTP mapping.

true

boolean

mapHttpMessageFormUrl EncodedBody (advanced)

If this option is true then IN exchange Form Encoded body of the exchange will be mapped to HTTP. Setting this to false will avoid the HTTP Form Encoded body mapping.

true

boolean

mapHttpMessageHeaders (advanced)

If this option is true then IN exchange Headers of the exchange will be mapped to HTTP headers. Setting this to false will avoid the HTTP Headers mapping.

true

boolean

synchronous (advanced)

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

false

boolean

proxyAuthScheme (proxy)

Proxy authentication scheme to use

 

String

proxyHost (proxy)

Proxy hostname to use

 

String

proxyPort (proxy)

Proxy port to use

 

int

authHost (security)

Authentication host to use with NTML

 

String

10.2. URI Format

atmosphere-websocket:///relative path[?options]

10.3. Reading and Writing Data over Websocket

An atmopshere-websocket endpoint can either write data to the socket or read from the socket, depending on whether the endpoint is configured as the producer or the consumer, respectively.

10.4. Configuring URI to Read or Write Data

In the route below, Camel will read from the specified websocket connection.

from("atmosphere-websocket:///servicepath")
        .to("direct:next");

And the equivalent Spring sample:

<camelContext xmlns="http://camel.apache.org/schema/spring">
  <route>
    <from uri="atmosphere-websocket:///servicepath"/>
    <to uri="direct:next"/>
  </route>
</camelContext>

In the route below, Camel will read from the specified websocket connection.

from("direct:next")
        .to("atmosphere-websocket:///servicepath");

And the equivalent Spring sample:

<camelContext xmlns="http://camel.apache.org/schema/spring">
  <route>
    <from uri="direct:next"/>
    <to uri="atmosphere-websocket:///servicepath"/>
  </route>
</camelContext>
 

10.5. See Also