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:

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");

In the route above, notice spel is a static method which we need to import from org.apache.camel.language.spel.SpelExpression.spel, as we use spel as an Expression passed in as a parameter to the setBody method. Though if we use the fluent API we can do this instead:

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

Notice we now use the spel method from the setBody() method. And this does not require us to static import the spel method from org.apache.camel.language.spel.SpelExpression.spel.

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");

Loading script from external resource

Available as of Camel 2.11

You can externalize the script and have Camel load it from a resource such as "classpath:", "file:", or "http:".
This is done using the following syntax: "resource:scheme:location", eg to refer to a file on the classpath you can do:

.setHeader("myHeader").spel("resource:classpath:myspel.txt")

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>