Java annotation processing with source code manipulation

The standard annotation processing API does not support direct modification of source code. However, some of the effects of modifying source code can be had by generating either the superclass or subclass(es) of the annotated type. The blog entry below shows an example of this technique:

"Properties via Annotation Processing"

You can do this as something below which will let you accomplish 3) and 4).

Example taken from java annotation processor example

@SupportedAnnotationTypes( "com.javacodegeeks.advanced.processor.Immutable" )
@SupportedSourceVersion( SourceVersion.RELEASE_7 )
public class SimpleAnnotationProcessor extends AbstractProcessor {
  @Override
  public boolean process(final Set< ? extends TypeElement > annotations, 
      final RoundEnvironment roundEnv) {

    for( final Element element: roundEnv.getElementsAnnotatedWith( Immutable.class ) ) {
      if( element instanceof TypeElement ) {
        final TypeElement typeElement = ( TypeElement )element;

        for( final Element eclosedElement: typeElement.getEnclosedElements() ) {
       if( eclosedElement instanceof VariableElement ) {
           final VariableElement variableElement = ( VariableElement )eclosedElement;

           if( !variableElement.getModifiers().contains( Modifier.FINAL ) ) {
             processingEnv.getMessager().printMessage( Diagnostic.Kind.ERROR,
               String.format( "Class '%s' is annotated as @Immutable, 
                 but field '%s' is not declared as final", 
                 typeElement.getSimpleName(), variableElement.getSimpleName()            
               ) 
             );                     
           }
         }
       }
    }

    // Claiming that annotations have been processed by this processor 
    return true;
  }
}

Another way using projectlombok with custom handler.

Example built in handler from GitHub Project Lombok. This annotation adds try catch block

public class SneakyThrowsExample implements Runnable {
    @SneakyThrows(UnsupportedEncodingException.class)
    public String utf8ToString(byte[] bytes) {
        return new String(bytes, "UTF-8");
    }

    @SneakyThrows
    public void run() {
        throw new Throwable();
    }
}

This gets processed to

public String utf8ToString(byte[] bytes) {
    try {
        return new String(bytes, "UTF-8");
    } catch (UnsupportedEncodingException e) {
        throw Lombok.sneakyThrow(e);
    }
}

public void run() {
    try {
        throw new Throwable();
    } catch (Throwable t) {
        throw Lombok.sneakyThrow(t);
    }
}

You can find the Handler code on the same Github/lombok site.

I would suggest you copy all of the source code to a separate directory, modify the code there and build from the temporary path.