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<p>When writing a script, it may be unwieldy to call the script defining the whole classpath at the command line, e.g. </p>

<p>  groovy -cp %JAXB_HOME%\bin\activation.jar;%JAXB_HOME%\bin\... myscript.groovy</p>

<p>You can go the other way - let the script itself find the jars it needs and add them to the classpath before using them. To do this, you need to </p>

<p>1. get the groovy rootloader</p>

<p>def loader = this.class.classLoader.rootLoader</p>

<p>2. introduce the necessary uls to groovy rootloader. Use whatever logic suits your situations to find the jars / class directories</p>

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def jardir = new File( System.getenv( 'JAXB_HOME' ), 'lib' )
def jars   = jardir.listFiles().findAll { it.name.endsWith('.jar') } 
jars.each { loader.addURL(it.toURI().toURL()) }
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<p>3. Load the classes you need:</p>

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// in a script run from command line this is ok:
JAXBContext = Class.forName( 'javax.xml.bind.JAXBContext' )
Marshaller  = Class.forName( 'javax.xml.bind.Marshaller' )

// if the groovy script / class is loaded from a java app, then the above may fail as it uses the same classloader to load the class as the containing script / class was loaded by. In that case, this should work:

JAXBContext = Class.forName( 'javax.xml.bind.JAXBContext', true, loader )
Marshaller  = Class.forName( 'javax.xml.bind.Marshaller', true, loader )
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<p>4. To instantiate the classes, use the newInstance method:</p>

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def jaxbContext = JAXBContext.newInstance( MyDataClass )
</pre></td></tr></table>

<p>Note that newInstance is on steroids when called from groovy. In addition to being able to call the parameterless constructor (as w/ Java's Class.newInstance()), you can give any parameters to invoke any constructor, e.g.</p>

<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
def i = MyClass.newInstance( "Foo", 12 ) // invokes the constructor w/ String and int as params
</pre></td></tr></table>

<p>You can also pass a map to initialize properties, e.g.</p>

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def i2 = MyClass.newInstance(foo:'bar', boo:12) // creates a new instance using the parameterless constructor and then sets property foo to 'bar' and property boo to 12
</pre></td></tr></table>

<p>The downside of using this approach is that you can't inherit from the classes you load this way - classes inherited from need to be known before the script starts to run.</p>