Generate code at compile time with Java?

Question

I've created a set of classes that represent RESTful resources, and other helper things that actually do the HTTP requests to retrieve and build objects. My classes look like this :

class MyResource{ Attribute id = new Attribute(this, long); Attribute name = new Attribute(this, String); /* etc */ }

Now it happens that I would like to use POJO classes in order to plug to a framework that likes to deal with POJOs.

I would like to have proxies that would look like this:

class MyResourceProxy{ private MyResource realResource; public MyResourceProxy(MyResource o){realResource = o;} public long getId(){ return realResource.id.get(); } public void setId(long value){ realResource.id.set(value); } public String getName(){ return realResource.name.get(); } public void setName(String value){ realResource.name.set(value); } }

I don't want to have to maintain code for those proxy classes, but only the "resource-type" master classes.

I looked into introspection and found a hint on how to generate the said proxy code on demand. The question is : is it possible to generate the code at compile-time, and then have it compiled along with the library? Maybe I've taken the wrong turn and I'm doing something uninteresting, though ;)

What do you think? Thanks!

If the client code is that dynamic, how is the user of your client code supposed to deal with that? — Jochen Bedersdorfer
– Jochen Bedersdorfer, Commented Mar 24, 2011 at 17:54
Well the client code user would know what classes/methods to use, but I want to make sure the proxy classes are always up-to-date. — Olivier H
– Olivier H, Commented Mar 25, 2011 at 10:47

Peter Lawrey · Accepted Answer · 2011-03-24 17:08:55Z

It depends on what you build system is, if you mean javac, then I would say no, but if you use ant or maven then you can.

There are lots of examples for code generators.

In your case I would use reflection on the compiled MyResource class. I would consider using Velocity to help template the class. It may be overkill in your case, but as you generate more code it may be useful.

Jason Brant · Accepted Answer · 2011-03-24 17:10:15Z

1

Have you tried using dependency injection to generate your classes on instantiation?

Basic example for DI

answered Mar 24, 2011 at 17:10

Jason Brant

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1 Comment

Olivier H Over a year ago

I would have like something lighter, but thanks for the hint.

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