Spring Expression Language (SpEL)

Available as of Camel 2.7

Camel allows SpEL to be used as an Expression or Predicate in the DSL or Xml Configuration.

Variables

The following variables are available in expressions and predicates written in SpEL:

Variable Type Description
this Exchange the Exchange is the root object
exchange Exchange the Exchange object
exception Throwable the Exchange exception (if any)
exchangeId String the exchange id
fault Message the Fault message (if any)
request Message the exchange.in message
response Message the exchange.out message (if any)
properties Map the exchange properties
property(name) Object the property by the given name
property(name, type) Type the property by the given name as the given type

Samples

Expression templating

SpEL expressions need to be surrounded by #{ } delimiters since expression templating is enabled. This allows you to combine SpEL expressions with regular text and use this as extremely lightweight template language.

For example if you construct the following route:

from("direct:example").setBody(spel("Hello #{request.body}! What a beautiful #{request.headers['dayOrNight']}")).to("mock:result");

And sent a message with the string "World" in the body, and a header "dayOrNight" with value "day":

template.sendBodyAndHeader("direct:example", "World", "dayOrNight", "day");

The output on mock:result will be "Hello World! What a beautiful day"

Bean integration

You can reference beans defined in the Registry (most likely an ApplicationContext) in your SpEL expressions. For example if you have a bean named "foo" in your ApplicationContext you can invoke the "bar" method on this bean like this:

#{@foo.bar == 'xyz'}

SpEL in enterprise integration patterns

You can use SpEL as an expression for Recipient List or as a predicate inside a Message Filter:

<route>
  <from uri="direct:foo"/>
  <filter>
    <spel>#{request.headers['foo'] == 'bar'}</spel>
    <to uri="direct:bar"/>
  </filter>
</route>

And the equivalent in Java DSL:

   from("direct:foo").filter().spel("#{request.headers['foo'] == 'bar'}").to("direct:bar");

Dependencies

You need Spring 3.0 or higher to use Spring Expression Language. If you use Maven you could just add the following to your pom.xml:

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