Undertow

Since Camel 2.16

The Undertow component provides HTTP and WebSocket based endpoints for consuming and producing HTTP/WebSocket requests.

That is, the Undertow component behaves as a simple Web server. Undertow can also be used as a http client which mean you can also use it with Camel as a producer.

Since the component also supports WebSocket connections, it can serve as a drop-in replacement for Camel websocket component or atmosphere-websocket component.

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

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

URI format

undertow:http://hostname[:port][/resourceUri][?options]
undertow:https://hostname[:port][/resourceUri][?options]
undertow:ws://hostname[:port][/resourceUri][?options]
undertow:wss://hostname[:port][/resourceUri][?options]

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

Options

The Undertow component supports 5 options, which are listed below.

Name Description Default Type

undertowHttpBinding (advanced)

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

UndertowHttpBinding

sslContextParameters (security)

To configure security using SSLContextParameters

SSLContextParameters

useGlobalSslContext Parameters (security)

Enable usage of global SSL context parameters.

false

boolean

hostOptions (advanced)

To configure common options, such as thread pools

UndertowHostOptions

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 Undertow endpoint is configured using URI syntax:

undertow:httpURI

with the following path and query parameters:

Path Parameters (1 parameters):

Name Description Default Type

httpURI

Required The url of the HTTP endpoint to use.

URI

Query Parameters (22 parameters):

Name Description Default Type

useStreaming (common)

For HTTP endpoint: if true, text and binary messages will be wrapped as java.io.InputStream before they are passed to an Exchange; otherwise they will be passed as byte. For WebSocket endpoint: if true, text and binary messages will be wrapped as java.io.Reader and java.io.InputStream respectively before they are passed to an Exchange; otherwise they will be passed as String and byte respectively.

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

optionsEnabled (consumer)

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

false

boolean

exceptionHandler (consumer)

To let the consumer use a custom ExceptionHandler. Notice if the option bridgeErrorHandler is enabled then this option 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

cookieHandler (producer)

Configure a cookie handler to maintain a HTTP session

CookieHandler

keepAlive (producer)

Setting to ensure socket is not closed due to inactivity

true

Boolean

options (producer)

Sets additional channel options. The options that can be used are defined in org.xnio.Options. To configure from endpoint uri, then prefix each option with option., such as option.close-abort=true&option.send-buffer=8192

Map

preserveHostHeader (producer)

If the option is true, UndertowProducer 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.

true

boolean

reuseAddresses (producer)

Setting to facilitate socket multiplexing

true

Boolean

tcpNoDelay (producer)

Setting to improve TCP protocol performance

true

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

transferException (producer)

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

headerFilterStrategy (advanced)

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

HeaderFilterStrategy

synchronous (advanced)

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

false

boolean

undertowHttpBinding (advanced)

To use a custom UndertowHttpBinding to control the mapping between Camel message and undertow.

UndertowHttpBinding

fireWebSocketChannelEvents (websocket)

if true, the consumer will post notifications to the route when a new WebSocket peer connects, disconnects, etc. See UndertowConstants.EVENT_TYPE and EventType.

false

boolean

sendTimeout (websocket)

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

30000

Integer

sendToAll (websocket)

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

Boolean

sslContextParameters (security)

To configure security using SSLContextParameters

SSLContextParameters

Spring Boot Auto-Configuration

When using Spring Boot make sure to use the following Maven dependency to have support for auto configuration:

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

The component supports 10 options, which are listed below.

Name Description Default Type

camel.component.undertow.enabled

Enable undertow component

true

Boolean

camel.component.undertow.host-options.buffer-size

The buffer size of the Undertow host.

Integer

camel.component.undertow.host-options.direct-buffers

Set if the Undertow host should use direct buffers.

Boolean

camel.component.undertow.host-options.http2-enabled

Set if the Undertow host should use http2 protocol.

Boolean

camel.component.undertow.host-options.io-threads

The number of io threads to use in a Undertow host.

Integer

camel.component.undertow.host-options.worker-threads

The number of worker threads to use in a Undertow host.

Integer

camel.component.undertow.resolve-property-placeholders

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

true

Boolean

camel.component.undertow.ssl-context-parameters

To configure security using SSLContextParameters. The option is a org.apache.camel.util.jsse.SSLContextParameters type.

String

camel.component.undertow.undertow-http-binding

To use a custom HttpBinding to control the mapping between Camel message and HttpClient. The option is a org.apache.camel.component.undertow.UndertowHttpBinding type.

String

camel.component.undertow.use-global-ssl-context-parameters

Enable usage of global SSL context parameters.

false

Boolean

Message Headers

Camel uses the same message headers as the HTTP component. It also uses Exchange.HTTP_CHUNKED,CamelHttpChunked header to turn on or turn off the chunked encoding on the camel-undertow consumer.

Camel also populates all request.parameter and request.headers. For example, given a client request with the URL, http://myserver/myserver?orderid=123, the exchange will contain a header named orderid with the value 123.

HTTP Producer Example

The following is a basic example of how to send an HTTP request to an existing HTTP endpoint.

in Java DSL

from("direct:start")
    .to("undertow:http://www.google.com");

or in XML

<route>
    <from uri="direct:start"/>
    <to uri="undertow:http://www.google.com"/>
<route>

HTTP Consumer Example

In this sample we define a route that exposes a HTTP service at http://localhost:8080/myapp/myservice:

<route>
  <from uri="undertow:http://localhost:8080/myapp/myservice"/>
  <to uri="bean:myBean"/>
</route>

WebSocket Example

In this sample we define a route that exposes a WebSocket service at http://localhost:8080/myapp/mysocket and returns back a response to the same channel:

<route>
  <from uri="undertow:ws://localhost:8080/myapp/mysocket"/>
  <transform><simple>Echo ${body}</simple></transform>
  <to uri="undertow:ws://localhost:8080/myapp/mysocket"/>
</route>

Using localhost as host

When you specify localhost in a URL, Camel exposes the endpoint only on the local TCP/IP network interface, so it cannot be accessed from outside the machine it operates on.

If you need to expose an Undertow endpoint on a specific network interface, the numerical IP address of this interface should be used as the host. If you need to expose an Undertow endpoint on all network interfaces, the 0.0.0.0 address should be used.

To listen across an entire URI prefix, see How do I let Jetty match wildcards.

If you actually want to expose routes by HTTP and already have a Servlet, you should instead refer to the Servlet Transport.

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