Groovy

Since Camel 1.3

Camel has support for using Groovy.

For example, you can use Groovy in a Predicate with the Message Filter EIP.

groovy("someGroovyExpression")

Groovy Options

The Groovy language supports 2 options, which are listed below.

Name Default Java Type Description

resultType

String

Sets the class of the result type (type from output).

trim

true

Boolean

Whether to trim the value to remove leading and trailing whitespaces and line breaks.

Examples

In the example below we use a groovy script as predicate in the message filter, to determine if any line items is over $100:

// lets route if a line item is over $100
from("queue:foo")
    .filter(groovy("request.lineItems.any { i -> i.value > 100 }"))
        .to("queue:bar")

And in XML DSL:

<route>
    <from uri="queue:foo"/>
    <filter>
        <groovy>request.lineItems.any { i -> i.value > 100 }</groovy>
        <to uri="queue:bar"/>
    </filter>
</route>

Groovy Context

Camel will provide exchange information in the Groovy context (just a Map). The Exchange is transferred as:

key value

exchange

The Exchange itself.

exchangeProperties

The Exchange properties.

variables

The variables

headers

The headers of the In message.

camelContext

The Camel Context.

request

The In message.

body

The In message body.

response

The Out message (only for InOut message exchange pattern).

How to get the result from multiple statements script

As the Groovy script engine evaluate method just return a Null if it runs a multiple statements script. Camel now look up the value of script result by using the key of "result" from the value set. If you have multiple statements script, you need to make sure you set the value of result variable as the script return value.

bar = "baz";
# some other statements ...
# camel take the result value as the script evaluation result
result = body * 2 + 1

Customizing Groovy Shell

For very special use-cases you may need to use a custom GroovyShell instance in your Groovy expressions. To provide the custom GroovyShell, add an implementation of the org.apache.camel.language.groovy.GroovyShellFactory SPI interface to the Camel registry.

public class CustomGroovyShellFactory implements GroovyShellFactory {

  public GroovyShell createGroovyShell(Exchange exchange) {
    ImportCustomizer importCustomizer = new ImportCustomizer();
    importCustomizer.addStaticStars("com.example.Utils");
    CompilerConfiguration configuration = new CompilerConfiguration();
    configuration.addCompilationCustomizers(importCustomizer);
    return new GroovyShell(configuration);
  }

}

Camel will then use your custom GroovyShell instance (containing your custom static imports), instead of the default one.

Loading script from external resource

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").groovy("resource:classpath:mygroovy.groovy")

Dependencies

To use scripting languages in your camel routes you need to add a dependency on camel-groovy.

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

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