Chapter 331. Undertow Component

Available as of Camel version 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.

Tip

Since Camel version 2.21, the undertow component also supports WebSocket connections and can thus 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>

331.1. 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&…​

331.2. Options

The Undertow component supports 5 options which are listed below.

NameDescriptionDefaultType

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:

331.2.1. Path Parameters (1 parameters):

NameDescriptionDefaultType

httpURI

Required The url of the HTTP endpoint to use.

 

URI

331.2.2. Query Parameters (21 parameters):

NameDescriptionDefaultType

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 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

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

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

useStreaming (websocket)

if true, text and binary messages coming through a WebSocket 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

sslContextParameters (security)

To configure security using SSLContextParameters

 

SSLContextParameters

331.3. Message Headers

Camel uses the same message headers as the HTTP component. From Camel 2.2, it also uses Exchange.HTTP_CHUNKED,CamelHttpChunked header to turn on or turn off the chuched 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.

331.4. 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>

331.5. 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>

331.6. 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>

331.7. 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 a Jetty endpoint on a specific network interface, the numerical IP address of this interface should be used as the host. If you need to expose a Jetty 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.

331.8. Undertow consumers on {wildfly}

The configuration of camel-undertow consumers on {wildfly} is different to that of standalone Camel. Producer endpoints work as per normal.

On {wildfly}, camel-undertow consumers leverage the default Undertow HTTP server provided by the container. The server is defined within the undertow subsystem configuration. Here’s an excerpt of the default configuration from standalone.xml:

<subsystem xmlns="urn:jboss:domain:undertow:4.0">
    <buffer-cache name="default" />
    <server name="default-server">
        <http-listener name="default" socket-binding="http" redirect-socket="https" enable-http2="true" />
        <https-listener name="https" socket-binding="https" security-realm="ApplicationRealm" enable-http2="true" />
        <host name="default-host" alias="localhost">
            <location name="/" handler="welcome-content" />
            <filter-ref name="server-header" />
            <filter-ref name="x-powered-by-header" />
            <http-invoker security-realm="ApplicationRealm" />
        </host>
    </server>
</subsystem>

In this instance, Undertow is configured to listen on interfaces / ports specified by the http and https socket-binding. By default this is port 8080 for http and 8443 for https.

This has the following implications:

  • camel-undertow consumers will only bind to localhost:8080 or localhost:8443
  • Some endpoint consumer configuration options have no effect (see below), since these settings are managed by the {wildfly} container

For example, if you configure an endpoint consumer using different host or port combinations, a warning will appear within the server log file. For example the following host & port configurations would be ignored:

from("undertow:http://somehost:1234/path/to/resource")
[org.wildfly.extension.camel] (pool-2-thread-1) Ignoring configured host: http://somehost:1234/path/to/resource

However, the consumer is still available on the default host & port localhost:8080 or localhost:8443.

331.8.1. Configuring alternative ports

If alternative ports are to be accepted, then these must be configured via the {wildfly} subsystem configuration. This is explained in the server documentation:

https://access.redhat.com/documentation/en-us/red_hat_jboss_enterprise_application_platform/7.1/html/configuration_guide/configuring_the_web_server_undertow

331.8.2. Ignored camel-undertow consumer configuration options on {wildfly}

hostOptions

Refer to the {wildfly} undertow configuration guide for how to configure server host options:

https://access.redhat.com/documentation/en-us/red_hat_jboss_enterprise_application_platform/7.1/html-single/how_to_configure_server_security/#configure_one_way_and_two_way_ssl_tls_for_application

sslContextParameters

To configure SSL, refer to the {wildfly} SSL configuration guide:

https://access.redhat.com/documentation/en-us/red_hat_jboss_enterprise_application_platform/7.1/html-single/how_to_configure_server_security/#configure_one_way_and_two_way_ssl_tls_for_application