Step 4: Create the appropriate computation service

• Create a new package, named org.decisiondeck.mytest.computation.
• Create a new class in this package, and named it WeightedSum. It should extend AlternativeDependentComputation and implement IComputation.
• Implement the weighted sum method in the compute function, and update the name and discriminant functions.

  public class WeightedSum extends AlternativeDependentComputation implements
                  IComputation {
  
          static public final String NAME = "WeightedSum";
          static public final String LOGICAL_NAME = "NewWeightedSum";
          
          public Object compute(User user) {
                  AbstractAlternative alt = getAlternative1();
  
                  List<AbstractEntity> entities = MyBeanService.getInstance().getAll(user);
                  
                  float weightedSum = 0;
                  float totalWeight = 0;
                  
                  // Browse the weights given by the relevant user
                  // each weight has a float value and is related to a criterion
                  for (AbstractEntity entity:entities)
                  {
                          if (entity instanceof MyBean)
                          {
                                  MyBean bean = (MyBean) entity;
                                  
                                  Float weight = bean.getWeight();
                                  ICriteria criterion = bean.getCriterion();
                                  
                                  float localSum = 0;
                                  float numEvaluator = 0;
  
                                  // Browse all the evaluators to have a mean value (among evaluators)
                                  // of the valuation of alt wrt criterion
                                  for (Iterator iter = EvaluatorService.getEvaluators().iterator(); iter.hasNext();)
                                  {
                                          Evaluator evaluator = (Evaluator) iter.next();
                                          Float valuation = evaluator.getEvaluations().getAnswer(alt, criterion);
                                          
                                          if (valuation != null)
                                          {
                                                  localSum += valuation;
                                                  numEvaluator++;
                                          }
                                  }
                                  
                                  if (numEvaluator!=0 && weight!=null)
                                  {
                                          float contribution = localSum/numEvaluator;
                                          weightedSum += weight.floatValue()*contribution;
                                          totalWeight += weight.floatValue();
                                  }
                          }
                  }
                  if (totalWeight !=0)
                  {
                          return weightedSum/totalWeight;
                  }
                  return 0;
          }
  
          public String getDiscriminant() {
                  return WeightedSum.NAME;
          }
  
          public String getName() {
                  return WeightedSum.NAME;
          }
  
          public String getSecondaryDiscriminant() {
                  return WeightedSum.LOGICAL_NAME;
          }
  
  }
  

  It is necessary to add the following imports

  import org.decisiondeck.model.alternative.AbstractAlternative;
  import org.decisiondeck.model.AbstractEntity;
  import java.util.List;
  import java.util.Iterator;
  import org.decisiondeck.mytest.model.MyBean;
  import org.decisiondeck.mytest.service.MyBeanService;
  import org.decisiondeck.model.evaluation.ICriteria;
  import org.decisiondeck.model.evaluation.Evaluator;
  import org.decisiondeck.service.EvaluatorService;
  

Next Step

Build the view layer.