//Listing 5.18 IndentedLogging.java: a reusable base aspect to get indentation behavior

package logging;

public abstract aspect IndentedLogging {
    protected int _indentationLevel = 0;

    protected abstract pointcut loggedOperations();

    before() : loggedOperations() {
	_indentationLevel++;
    }

    after() : loggedOperations() {
	_indentationLevel--;
    }

    before() : call(* java.io.PrintStream.println(..))
	&& within(IndentedLogging+) {
	for (int i = 0, spaces = _indentationLevel * 4;
	     i < spaces; ++i) {
	    System.out.print(" ");
	}
    }
}