BeanShell

Camel supports BeanShell among other Scripting Languages to allow an Expression or Predicate to be used in the DSL or Xml Configuration.

To use a BeanShell expression use the following Java code:

...choice()
    .when(script("beanshell", "request.getHeaders().get(\"foo\").equals(\"bar\")"))
       .to("...")

Or the something like this in your Spring XML:

<filter>
  <language language="beanshell">request.getHeaders().get("Foo") == null</language>
  ...

You could follow the examples above to create an Predicate in a Message Filter or as an Expression for a Recipient List

ScriptContext

The JSR-223 scripting languages ScriptContext is pre configured with the following attributes all set at ENGINE_SCOPE:

Attributes

You can add your own attributes with the attribute(name, value) DSL method, such as:

In the sample below we add an attribute user that is an object we already have instantiated as myUser. This object has a getFirstName() method that we want to set as header on the message. We use the groovy language to concat the first and last name into a single string that is returned.

from("direct:in").setHeader("name").groovy("'$user.firstName $user.lastName'").attribute("user", myUser).to("seda:users");

Any scripting language

Camel can run any JSR-223 scripting languages using the script DSL method such as:

from("direct:in").setHeader("firstName").script("jaskel", "user.firstName").attribute("user", myUser).to("seda:users");

This is a bit different using the Spring DSL where you use the expression element that doesn't support setting attributes (yet):

    <from uri="direct:in"/>
    <setHeader headerName="firstName">
        <expression language="jaskel">user.firstName</expression>
    </setHeader>
    <to uri="seda:users"/>

You can also use predicates e.g. in a Filter:

    <filter>
        <language language="beanshell">request.getHeaders().get("Foo").equals("Bar")</language>
        <to uri="direct:next" />
    </filter>

See Scripting Languages for the list of languages with explicit DSL support.

Some languages without specific DSL support but known to work with these generic methods include:

Additional arguments to ScriptingEngine

Available as of Camel 2.8

You can provide additional arguments to the ScriptingEngine using a header on the Camel message with the key CamelScriptArguments.
See this example:

    public void testArgumentsExample() throws Exception {
        if (!ScriptTestHelper.canRunTestOnThisPlatform()) {
            return;
        }

        getMockEndpoint("mock:result").expectedMessageCount(0);
        getMockEndpoint("mock:unmatched").expectedMessageCount(1);

        // additional arguments to ScriptEngine
        Map<String, Object> arguments = new HashMap<String, Object>();
        arguments.put("foo", "bar");
        arguments.put("baz", 7);

        // those additional arguments is provided as a header on the Camel Message
        template.sendBodyAndHeader("direct:start", "hello", ScriptBuilder.ARGUMENTS, arguments);

        assertMockEndpointsSatisfied();
    }

Using properties function

Available as of Camel 2.9

If you need to use the Properties component from a script to lookup property placeholders, then its a bit cumbersome to do so.
For example to set a header name myHeader with a value from a property placeholder, which key is provided in a header named "foo".

.setHeader("myHeader").groovy("context.resolvePropertyPlaceholders('{{' + request.headers.get('foo') + '}}')")

From Camel 2.9 onwards you can now use the properties function and the same example is simpler:

.setHeader("myHeader").groovy("properties.resolve(request.headers.get('foo'))")

Dependencies

To use scripting languages in your camel routes you need to add the a dependency on camel-script which integrates the JSR-223 scripting engine.

If you use maven you could just add the following to your pom.xml, substituting the version number for the latest & greatest release (see the download page for the latest versions).

<dependency>
  <groupId>org.apache.camel</groupId>
  <artifactId>camel-script</artifactId>
  <version>x.x.x</version>
</dependency>