Groovy DSL

About the Groovy DSL

The Groovy DSL implementation is built on top of the existing Java-based DSL, but it additionally allows to use Groovy language features in your routes, particularly Closures acting as Processor, Expression, Predicate, or Aggregation Strategy.
With the Groovy DSL you write your RouteBuilder classes entirely in Groovy, while the scripting component allows to embed small scripts into Java routes. The Groovy DSL requires Groovy 2.0 or newer and is available as of Camel 2.11.

Introduction

Because Groovy is syntactically very similar to Java, you can write your Groovy routes just like Java routes. The same Java DSL classes are being used, with the exception that some of the DSL classes get extended with a bunch of new methods at runtime. This is achieved by turning camel-groovy into a Groovy Extension Module that defines extension methods on existing classes.

The majority of the extension methods allow Closures to be used as parameters e.g. for expressions, predicates, processors. The following example reverses a string in the message body:

...
   from('direct:test')
      .transform { it.in.body.reverse() }
...

The corresponding route in Java would look something like this:

...
   from('direct:test')
      .transform(new Expression() {
         public Object evaluate(Exchange e) {
            return new StringBuffer(e.getIn().getBody().toString()).reverse().toString();
         }
      });
   }
...

Using Closures

Using Groovy XML processing

Custom DSL extensions

Developing with the Groovy DSL

To be able to use the Groovy DSL in your camel routes you need to add the a dependency on camel-groovy which implements the Groovy DSL.

If you use Maven you can 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-groovy</artifactId>
  <version>2.11.0</version>
</dependency>

Additionally you need to make sure that the Groovy classes will be compiled. You can either use gmaven for this or, particularly with mixed projects containing Java and Groovy code, you might want to use the Groovy Eclipse compiler:

  <plugin>
    <artifactId>maven-compiler-plugin</artifactId>
    <configuration>
      <compilerId>groovy-eclipse-compiler</compilerId>
    </configuration>
    <dependencies>
      <dependency>
        <groupId>org.codehaus.groovy</groupId>
        <artifactId>groovy-eclipse-compiler</artifactId>
	<version>2.7.0-01</version>
      </dependency>
    </dependencies>
  </plugin>

As Eclipse user, you might want to configure the Maven Eclipse plugin in a way so that your project is set up correctly for using Eclipse Plugin for Groovy when mvn eclipse:eclipse is executed:

  <plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-eclipse-plugin</artifactId>
    <configuration>
      <additionalProjectnatures>
        <projectnature>org.eclipse.jdt.groovy.core.groovyNature</projectnature>
      </additionalProjectnatures>
      <classpathContainers>
        <classpathContainer>org.eclipse.jdt.launching.JRE_CONTAINER</classpathContainer>
        <classpathContainer>GROOVY_DSL_SUPPORT</classpathContainer>
      </classpathContainers>              
    </configuration>
  </plugin>