Working with JBI Properties
In ServiceMix you can access the JBI message properties as a Map and work natively with it in Groovy using various mechanisms. e.g.

// lets output some message properties
outMessage.properties.foo = "hello"
outMessage.properties.someList = [1, 2, 3]

or use an intermediate object if you've lots of properties to set

def props = outMessage.properties
props.foo = "hello"
props.someList = [1, 2, 3]

or just use the native Map/property syntax

outMessage.properties = [foo:"hello", someList:[1, 2, 3]]

Generating Output
Groovy provides various mechanism for generating the output (whether it is the result of a service or a transformation). Which mechnism you use depends on your use case and personal preference.

String Templates
You can use Groovy string templates to output XML, which is a nice, simple way to generate blocks of XML with dynamic content:

outMessage.bodyText = """
<hello>
  <world person="$inMessage.properties.name"/>
</hello>
"""

Notice the user above of the input messages's 'name' property, which is equivalent to the expression

inMessage.getProperty("name")

POJO Return Values
You can return a POJO as the body of a message - which other components can either transform or the default Marshaler will figure out the right thing to do.

// lets output the body as a POJO
outMessage.body = [3, 2, 1]

Using Groovy Markup
Groovy supports a simple and concise markup mechanism which can be used to programatically generate some XML markup (either DOM, SAX or any other XML model) while retaining the full power of Groovy within the control flow of the markup.

// lets output some XML using GroovyMarkup
outMessage.body = builder.hello(version:1.2) {
  world(person:inMessage.properties.name, location:'London')
}

Conclusion
If you are interested in SOA, EDA and integration please take a look at the ServiceMix project and see if it can help you. We welcome contributions!

Resource ServiceMix: http://servicemix.org/