Code Generation Using Annotation Processing

Question

I'm trying to figure out how to do something like thus:
Given this source file with the following custom annotation:
@Composite(interfaces=Mammal.class)
public class Dog implements IComposite
};I want to create an annotation processor that inserts a data member, implementation into the constructor, and a public method into this class:
@Composite(interfaces=Mammal.class)
public class Dog implements IComposite
    IComponent[] m_inner_objects;
    public Dog()
        m_inner_objects = new IComponent[1];
        m_inner_objects[0] = Mammal.compose(this);
    public IComponent getComponent(Class<?> inInterface)
        if(inInterface == Mammal.class)
           return m_inner_objects[0];
        return null;
};Are all three tasks possible? Are any of the three tasks possible? If yes to any of my questions how would I go about this. I've gotten just past the 'hello world' state in writing a custom annotation processor so I just need the more advanced knowledge of how to actually affect the code once I'm actively processing it.
cheers,

Answer 1

brucechapman wrote:
sednivo wrote:
I can get the CompilationUnitTree. Yes
Then I can modify it with Compiler Tree API.Really?
Where is a pitfall in my train of thought?The Tree API is an immutable API, you can look, but not modify.Here is example of modifying compiler tree.
http://svntrac.hanhuy.com/repo/browser/hanhuy/trunk/panno/src/com/hanhuy/panno/processing/PropertyProcessor.java
Also, the javax.annotation.processing.Filer will not allow you to overwrite an existing compilation unit, and you must use the Filer if you wish a generated class to be compiled in the next round.I don't use Filer class. Method writeCompilationUnit that I've wrote works well for existed files.
There is a fundamental principle of java that the same program always has the same meaning. See the 3rd paragraph of the Preface to the first edition of the Java Language Spec . >This is the reason why you can't modify existing source code.We can mark generated methods in a class with @Generated annotation.