I miss my monkeypatch.
If you have done a decent amount of python code, you’ve probably run into monkey patching – if you haven’t, you’re missing out. But in java, where I use an ever increasing number of open source libraries, I missed this lovely feature I was able to use to good effect in Plone. But no more, now there is AspectJ to the rescue.
First off, the problem I had was to extend the code generation capabilities in Axis 1.3 to generate java code from a WSDL (which is better than the other way around). But WSDL2Java extension is limited, and I don’t feel like downloading all the Axis source and changing it and recompiling it myself. All I wanted to do was to make the java code that was created include a unique ID to make the objects easier to persist in hibernate (and just to be a show-off, yes I am using Spring too, but not for code generation – it’s not good for everything :).
So how to do it? Easy enough, use the cuckoo’s egg design pattern to replace Axis’s current java class generator with an instance of my own when the constructor is called:
import java.util.Vector;
import org.apache.axis.wsdl.symbolTable.TypeEntry;
import org.apache.axis.wsdl.toJava.Emitter;
import org.apache.axis.wsdl.toJava.JavaBeanWriter;
import org.apache.axis.wsdl.toJava.JavaWriter;
import org.kookster.PersistentJavaBeanWriter;
/**
* Use this to change the behaviour of the WSDL2Java axis code gen
*
* @author kookster
*/
public aspect ReplaceJavaBeanWriterAspect {
//here's a pointcut to get the public constructor of Axis JavaBeanWriter
public pointcut javaBeanWriterConstructor( Emitter emitter,
TypeEntry type,
Vector elements,
TypeEntry extendType,
Vector attributes,
JavaWriter helper ):
call( JavaBeanWriter.new( Emitter,TypeEntry,Vector,TypeEntry,Vector,JavaWriter )) &&
args( emitter,type,elements,extendType,attributes,helper );
//here is the advice which calls the constructor for my object instead
JavaBeanWriter around( Emitter emitter,
TypeEntry type,
Vector elements,
TypeEntry extendType,
Vector attributes,
JavaWriter helper) :
javaBeanWriterConstructor( emitter,type,elements,extendType,attributes,helper )
{
return new PersistentJavaBeanWriter(emitter,type,elements,extendType,attributes,helper);
}
}