[Springframework-developer] added jython scripting support to spring

[John C. <joh...@gm...>]

I felt it was important to add jython support since the python
following is still strong.

Also looks like the jython project is becoming more active with
ambitions to sync up to the latest version of c python.

i still like python... call me old school.

so anyway this is what I did:

I created an extension to the spring-lang-2.0.xsd:

	<xsd:element name="jython" type="dynamicScriptType">
		<xsd:annotation>
			<xsd:documentation><![CDATA[
	A Spring bean backed by a Jython class definition.
			]]></xsd:documentation>
		</xsd:annotation>
	</xsd:element>

Then added a package org.springframework.scripting.jython with the
following sources added: JythonScriptFactory.java

In "getScriptedObject" perform the following:

	public Object getScriptedObject(ScriptSource actualScriptSource,
Class[] actualInterfaces)
			throws IOException, ScriptCompilationException {
		try {
			PythonInterpreter.initialize(System.getProperties(),null, new String[] {});
			PythonInterpreter interpreter = new PythonInterpreter();
			interpreter.exec(actualScriptSource.getScriptAsString());
			PyStringMap locals = (PyStringMap) interpreter.getLocals();
			PyList list = locals.values();
			PyClass clazz = null;
			for (int i=0; i < list.__len__(); i++) {
				PyObject py = list.__getitem__(i);
				if ((py instanceof PyClass) && !(py instanceof PyJavaClass)) {
					if (clazz != null) throw new PyException(new PyString("multiple
python class declarations present"));
					clazz = (PyClass) py;
				}
			}
			PyInstance instance = (PyInstance) clazz.__call__();
			return instance.__tojava__(actualInterfaces[0]);
		}
		catch (PyException ex) {
			throw new ScriptCompilationException("Could not compile Jython
script: " + actualScriptSource, ex);
		}
	}


This is just a POC.  It would be nice if we could specify the class
name as part of the ScriptSource object so we don't have to guess
which in the locals namespace class we are interested in.

Also in the org.springframework.scripting.config.LangNamespaceHandler
I add to the init method:

		if (ClassUtils.isPresent("org.python.core.PyObject")) {
			registerBeanDefinitionParser("jython", new
ScriptBeanDefinitionParser(JythonScriptFactory.class));
		}

So here is an excerpt from a beans file:

	<bean id="SPAM" class="jcoppola.atsi.application.SetRunnableTest">
		<property name="runnable" ref="runnable1"/>
	</bean>
	
	<bean id="EGGS" class="jcoppola.atsi.application.SetRunnableTest">
		<property name="runnable" ref="runnable2"/>
	</bean>
	
	<lang:jython id="runnable1" script-interfaces="java.lang.Runnable">
		<lang:inline-script>
from java.lang import Runnable
			
class JythonRunnable(Runnable):
	def __init__(self):
		print "__init__: JythonRunnable1"
	def run(self):
		print "run: JythonRunnable1"				
		</lang:inline-script>
	</lang:jython>

	<lang:jython id="runnable2" script-interfaces="java.lang.Runnable">
		<lang:inline-script>
from java.lang import Runnable
		
class JythonRunnable(Runnable):
	def __init__(self):
		print "__init__: JythonRunnable2"
	def run(self):
		print "run: JythonRunnable2"				
		</lang:inline-script>
	</lang:jython>

I'll provide a patch if this gains traction.

Cheers,
John Coppola