Providing Support for Extracting Concerns towards JAsCo Artifacts in the Concern Manipulation Environment

Type: Apprenticeship and Thesis

Assistant(s): Wim Vanderperren, Davy Suvee
Supervisor: Viviane Jonckers

Part of Thesis and/or Apprenticeship Projects 2004-2005

Karel Bernolet
Program: Licentiaat Toegepaste Informatica
E-mail: kbernole@vub.ac.be

The purpose of the apprenticeship is to support the extraction of concerns in the CME ¹⁾ towards JAsCo ²⁾.
Since the CME itself has no support yet for extraction, the main goal is to provide a framework to extract concerns. The CME will be used to identify and encapsulate a concern. Those concerns will be extracted towards JAsCo artifacts.
Len Feremans, an other student, provides support for JAsCo artifacts within the CME.

Here a simple scenario is demonstrated:

• We start with a regular java class containg a crosscutting concern.

package stock;
import logging.Logger;
public class Stock {
        public int counter;
 
        public Stock(int begin) {
                counter = begin;
        }
 
        public void add(int num) {
                counter += num;
                Logger.log("added " + num + counter);
        }
 
        public void remove(int num) {
                counter -= num;
                Logger.log("removed " + num + counter);
        }
 
        public int getStock() {
                int tmptmp = 3;
                int tmp = 20 + tmptmp;
                Logger.log("tmp var is:" + tmp+
                        " requested counter is: "+counter);
                return counter;
        }
}

• The CME query engine is used to identify all artifacts of the concern:

• and to construct the concern:

• the context menu of the concern is expanded with an option to extract the concern to JasCo artifacts:

• next a wizard pops up, allowing the developper to name the aspect, connector and a prefix of the generated hooks:

• the result of the refactoring is the same old class without the crosscutting concern:

package stock;
import logging.Logger;
public class Stock {
        public int counter;
        public Stock(int begin) {
                counter = begin;
        }
        public void add(int num) {
                counter += num;
        }
        public void remove(int num) {
                counter -= num;
        }
        public int getStock() {
                return counter;
        }
        public int getCounter() {
                return counter;
        }
}

• a connector describing where the aspect has to be applied:

static connector LogConnector {
  LogAspect.LogHook0 hook0 =
    new LogAspect.LogHook0(int stock.Stock.getStock());
  LogAspect.LogHook1 hook1 =
    new LogAspect.LogHook1(void stock.Stock.remove(int));
  LogAspect.LogHook2 hook2 =
    new LogAspect.LogHook2(void stock.Stock.add(int));
 
  hook0.after();
  hook1.after();
  hook2.after();
}

• and the aspect itself:

package aspects;
class LogAspect {
 
  hook LogHook0 {
    LogHook0(method(..args)) {
      execute(method);
    }
    after() {
      int tmptmp = 3;
      int tmp = 20 + tmptmp;
      Logger.log(
        "tmp var is:"
          + tmp
          + " requested calledobject.getCounter() is: "
          + calledobject.getCounter());
    }
  }
  hook LogHook1 {
    LogHook1(method(..args)) {
      execute(method);
    }
    after() {
      Logger.log(
        "removed " + arg[0] + calledobject.getCounter());
    }
  }
  hook LogHook2 {
    LogHook2(method(..args)) {
      execute(method);
    }
    after() {
      Logger().log(
        "added " + arg[0] + calledobject.getCounter());
    }
  }
}

• since the CME query engine only supports artifacts of 1 line, this system is limited to 1 line concerns as well
• at the moment only method calls are supported as an artifact
• the system only generates after() advices no matter where the concern is situated in the original code
• when a variable is and needed in the advice and needed in the original code, the system causes code duplication

Not yet available

Not yet available

• Intermediate Presentation
• Apprenticeship Report
• Apprenticeship Presentation

• Original proposal (in Dutch)
• Concern Manipulation Environment
• JAsCo: An Aspect-Oriented approach tailored for Component Based Software Development