[CONF] Apache ServiceMix: Groovy (page edited)

confluence Thu, 12 Jun 2008 03:43:33 -0700

Page Edited : SM : Groovy

Groovy has been edited by Lars Heinemann (Jun 12, 2008).

Content:

Warning

This component has been deprecated in favor to servicemix-scripting component.

ServiceMix supports Groovy which allows Groovy scripts to be used as endpoints, transformers or services. This allows you to combine the power of the Groovy scripting language with the ServiceMix JBI container and any off the shelf JBI components to create a very flexible and agile integration solution.

The GroovyComponent is an extension of the Scripting support and supports the same variable bindings.

Example

Before we go into detail of how you can work with JBI and Groovy in ServiceMix, lets show a simple hello world kinda example.

<sm:activationSpec componentName="myServiceUsingXMLText"
        service="foo:myServiceUsingXMLText">
        <sm:component>
          <bean class="org.apache.servicemix.components.groovy.GroovyComponent">
            <property name="scriptText">
              <value>
                <![CDATA[


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

// lets output some non-xml body
outMessage.bodyText = """
<hello>
  <world person="$inMessage.properties.name" location="London"/>
</hello>
"""
                ]]>
              </value>
            </property>
          </bean>
        </sm:component>
      </sm:activationSpec>

As you can see the component is configured with a piece of Groovy to execute when the service is invoked. (BTW if you wanna see this script in action try the test case and XML config file.

Now we'll go through the various options which are available when working with JBI and Groovy in ServiceMix

Maintaining state across requests

Its often handy to keep track of state across requests. There is a variable called 'bindings' which you can use to maintain state...

<activationSpec componentName="myServiceImpl" service="foo:myServiceImpl">
      <component>
       <bean xmlns="" class="org.apache.servicemix.components.groovy.GroovyComponent">
        <property name="scriptText">
          <value>
            <![CDATA[
if (bindings.counter == null) {
    bindings.counter = 1
}
else {
    ++bindings.counter
}

def date = new Date()

outMessage.bodyText = "<response counter='$bindings.counter' date='$date'></response>"
            ]]>
          </value>
        </property>
      </bean></component></activationSpec>

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 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 mechanism 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')
}

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