Chapter 358. 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>

358.1. 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&…

358.2. 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:

358.2.1. Path Parameters (1 parameters):

Name	Description	Default	Type
httpURI	Required The url of the HTTP endpoint to use.		URI

358.2.2. Query Parameters (22 parameters):

Name	Description	Default	Type
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
handlers (consumer)	Specifies a comma-delimited set of `io.undertow.server.HttpHandler` instances to lookup in your Registry. These handlers are added to the Undertow handler chain, for example, to add security. Note You can not use different handlers with different Undertow endpoints using the same port number. The handlers is associated to the port number. If you need different handlers, then use different port numbers.		String
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

358.3. Spring Boot Auto-Configuration

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

358.4. 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.

358.5. 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>

358.6. 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>

358.7. 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>

358.8. HTTP/2 Example

In this sample, we configure the camel-undertow component to support the HTTP/2 protocol and expose a HTTP service at http://localhost:7766/foo/bar.

The directory structure of this sample is as follows:

├── pom.xml 1
├── README.md
└── src
    └── main
        └── resources
            └── META-INF
                └── spring
                    └── camel-context.xml 2

The following files are important for configuring the camel-undertow component to support the HTTP/2 protocol:

1

pom.xml: Includes the following properties and dependencies:

<properties>
    <camel.version>2.23.1</camel.version>
</properties>

<dependency>
    <groupId>org.apache.camel</groupId>
    <artifactId>camel-core</artifactId>
    <version>${camel.version}</version>
</dependency>
<dependency>
    <groupId>org.apache.camel</groupId>
    <artifactId>camel-spring</artifactId>
    <version>${camel.version}</version>
</dependency>
<dependency>
    <groupId>org.apache.camel</groupId>
    <artifactId>camel-undertow</artifactId>
    <version>${camel.version}</version>
    </dependency>
<dependency>
    <groupId>org.apache.camel</groupId>
    <artifactId>camel-http-common</artifactId>
    <version>${camel.version}</version>
</dependency>

<plugin>
    <groupId>org.apache.camel</groupId>
    <artifactId>camel-maven-plugin</artifactId>
    <version>${camel.version}</version>
    <configuration>
        <fileApplicationContextUri>src/main/resources/META-INF/spring/camel-context.xml</fileApplicationContextUri>
    </configuration>
</plugin>

2

camel-context.xml: Configures the camel-undertow component as follows:

<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://camel.apache.org/schema/spring http://camel.apache.org/schema/spring/camel-spring.xsd">
    <camelContext id="cbr-example-context" xmlns="http://camel.apache.org/schema/spring">
        <route id="cbr-route" trace="true">
            <from id="_from1" uri="undertow:http://localhost:7766/foo/bar"/>
            <setBody id="_setBody1">
                <constant>Sending Response</constant>
            </setBody>
            <log id="_log5" message="Headers ${in.headers}"/>
            <log id="_log5" message="Done processing ${body}"/>
        </route>
    </camelContext>
    <bean class="org.apache.camel.component.undertow.UndertowComponent" id="undertow">
        <property name="hostOptions" ref="undertowHostOptions"/>
    </bean>
    <bean     class="org.apache.camel.component.undertow.UndertowHostOptions" id="undertowHostOptions">
        <property name="http2Enabled" value="true"/>
    </bean>
</beans>

Note

The http2Enabled property which is set to false by default, is set to true for UndertowHostOptions class. This class is then referred to UndertowComponent which is used in camel route.

In this example, by using the camel-maven-plugin in the pom.xml file, we can expose a HTTP service at http://localhost:7766/foo/bar when we execute the Maven command mvn camel:run.

We can test this example using the curl command as follows:

$ curl -v --http2 http://localhost:7766/foo/bar
* Trying ::1...
* TCP_NODELAY set
* connect to ::1 port 7766 failed: Connection refused
* Trying 127.0.0.1...
* TCP_NODELAY set
* Connected to localhost (127.0.0.1) port 7766 (#0)
> GET /foo/bar HTTP/1.1
> Host: localhost:7766
> User-Agent: curl/7.53.1
> Accept: */*
> Connection: Upgrade, HTTP2-Settings
> Upgrade: h2c
> HTTP2-Settings: AAMAAABkAARAAAAAAAIAAAAA
>
< HTTP/1.1 101 Switching Protocols
< Connection: Upgrade
< Upgrade: h2c
< Date: Sun, 10 Dec 2017 08:43:58 GMT
* Received 101
* Using HTTP2, server supports multi-use
* Connection state changed (HTTP/2 confirmed)
* Copying HTTP/2 data in stream buffer to connection buffer after upgrade: len=0
* Connection state changed (MAX_CONCURRENT_STREAMS updated)!
< HTTP/2 200
< accept: */*
< http2-settings: AAMAAABkAARAAAAAAAIAAAAA
< breadcrumbid: ID-dhcppc1-1512886066149-0-25
< content-length: 16
< user-agent: curl/7.53.1
< date: Sun, 10 Dec 2017 08:43:58 GMT
<
* Connection #0 to host localhost left intact
Sending Response

358.9. 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.

358.10. 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.

358.10.1. 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

358.10.2. 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: