Modifying the signature of a type

Question

I am trying to programmatically change the signature of a type, to be precise I want to let a class implement an interface or to add implements SomeInterface to its signature in other words.

I get an object for the type as follows:

IType ejbType = jproject.findType(ejbClass);

Then I would expect ITypeto have a method like setSuperInterfaceNames(String[]) but there is only a method getSuperInterfaceNames().

Is there any possibility to satisfy my requirement with jdt?

Answer 1

You can use Eclipse AST to modify the code. Roughly, the steps are:

1) Parse the source file [CompilationUnit unit = parseAst(ejbType.getCompilationUnit())]

public static CompilationUnit parseAst(ICompilationUnit unit, SubMonitor progress) {
    ASTParser parser = ASTParser.newParser(AST.JLS8);
    parser.setSource(unit);
    parser.setResolveBindings(true);
    return (CompilationUnit)parser.createAST(progress);
}

2) Find the Type you want to modify in your CompilationUnit, by using the visitor pattern:

unit.accept(new ASTVisitor() {
    @Override
    public boolean visit(TypeDeclaration node) {
        IType type = (IType) node.resolveBinding().getTypeDeclaration().getJavaElement();
        if (ejbType.equals(type)) {
            modifyTypeDeclaration(node);
        }
        return false;
    }
});

3) Implement modifyTypeDeclaration(TypeDeclaration node).

I usualy use ASTRewrite to collect all changes to a compilation unit (*.java file), bevor writing it back, which looks something like this.

ICompilationUnit cu = ejbType.getCompilationUnit();
cu.becomeWorkingCopy(...);
CompilationUnit unit = parseAst(ejbType.getCompilationUnit())
final ASTRewrite rewrite = ASTRewrite.create(unit.getAST());
collectChangesToUnit(unit, rewrite);
cu.applyTextEdit(rewrite.rewriteAST(), ...);
cu.commitWorkingCopy(false, ...);

If your case is realy simple you could also modify the TypeDeclaration directly.