Apache Camel: JavaScript

JavaScript

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

To use a JavaScript expression use the following Java code

... javaScript("someJavaScriptExpression") ...

For example you could use the javaScript function to create an Predicate in a Message Filter or as an Expression for a Recipient List

Example

In the sample below we use JavaScript to create a Predicate use in the route path, to route exchanges from admin users to a special queue.

    from("direct:start")
        .choice()
            .when().javaScript("request.headers.get('user') == 'admin'").to("seda:adminQueue")
        .otherwise()
            .to("seda:regularQueue");

And a Spring DSL sample as well:

    <route>
        <from uri="direct:start"/>
        <choice>
            <when>
                <javaScript>request.headers.get('user') == 'admin'</javaScript>
                <to uri="seda:adminQueue"/>
            </when>
            <otherwise>
                <to uri="seda:regularQueue"/>
            </otherwise>
        </choice>
    </route>

ScriptContext

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

Attribute	Type	Value
context	`org.apache.camel.CamelContext`	The Camel Context
exchange	`org.apache.camel.Exchange`	The current Exchange
request	`org.apache.camel.Message`	The IN message
response	`org.apache.camel.Message`	The OUT message

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"/>

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>1.4.0</version>
</dependency>

JavaScript

Example

ScriptContext

Attributes

Any scripting language

Dependencies

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