WrapperActionElement.java :  » Inversion-of-Control » JICE » org » jicengine » element » Java Open Source

package org.jicengine.element;

import org.jicengine.operation.SimpleContext;
import org.jicengine.operation.OperationException;
import org.jicengine.operation.LocalContext;
import org.jicengine.operation.Context;
import org.jicengine.operation.Operation;
import org.jicengine.expression.*;
import java.util.List;
import java.util.ArrayList;

/**
 * <p>
 * WrapperActionElement adds an action to a VariableElement.
 * </p>
 * <p>
 * Useful way for example transforming VariableElements as property-setters:
 * wrap them inside a WrapperActionElement and set the
 * action-operation to the set-property.
 * </p>
 *
 * <p>
 * Design-note: currently, there's know way to give the action any parameters
 * besides the implicit 'parent' and 'this' objects and global objects.
 * (and we shouldn't create new data that is not available in the JIC-file?)
 * of course, the action-Operation can always be constructor so that it
 * won't need other parameters..
 * </p>
 * <p>
 * Copyright (C) 2004  Timo Laitinen
 * </p>
 * @author    .timo
 */

public class WrapperActionElement extends AbstractElement implements ActionElement {

  private Operation action;
  private VariableElement variableElement;

  public WrapperActionElement(VariableElement variableElement, Location location,  Operation action)
  {
    super(variableElement.getName(), location);
    this.action = action;
    this.variableElement = variableElement;
  }

  public boolean isExecuted(Context outerContext, Object parentInstance) throws ElementException
  {
    return this.variableElement.isExecuted(outerContext,parentInstance);
  }

  public void execute(Context globalContext, Object parentInstance) throws ElementException
  {
    // create the context.
    Context actionParameterContext = new SimpleContext();

    if( parentInstance != null ){
      actionParameterContext.addObject(VARIABLE_NAME_PARENT_INSTANCE, parentInstance);
    }

    // create the instance here as part of the execution
    Object instance = this.variableElement.getValue(globalContext, parentInstance);

    // add the instance to the context, if necessary.
    if( this.action.needsParameter(Element.VARIABLE_NAME_ELEMENT_INSTANCE) ){
      actionParameterContext.addObject(Element.VARIABLE_NAME_ELEMENT_INSTANCE, instance);
    }

    // NOTE: the 'parent' element should already be in the outerContext.


    // context-hierarchy: action + global.
    Context actionContext = new LocalContext(
      actionParameterContext,
      globalContext);

    try {
      this.action.execute(actionContext);
    } catch (OperationException e){
      // this way the location information is added to the exception.
      throw new ElementException("Failed to execute action " + this.action, e, getName(), getLocation());
    }
  }
}