PropertyValue.java

/*******************************************************************************
 * Copyright (c) 2008 Ralf Ebert
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 * Ralf Ebert - initial API and implementation
 *******************************************************************************/
package de.ralfebert.rcputils.properties;

import java.beans.PropertyDescriptor;
import java.util.ArrayList;
import java.util.List;

import org.eclipse.core.internal.databinding.beans.BeanPropertyHelper;

/**
 * PropertyValue: Resolves nested property Strings like "company.country.name".
 * 
 * Use like this:
 * 
 * <pre>
 * PropertyValue prop = new PropertyValue("country.name");
 * Object countryName = prop.getValue(someObject);
 * </pre>
 * 
 * This class allows to use JFace Data Binding property support to get and set
 * nested property values without observing them.
 * 
 * Please note that this class is not prepared for a case where the classes of
 * the objects change on the path to the property. For example, if you use
 * "country.name" on a "Company" object once, it expects a "Company" object you
 * use it the next time.
 * 
 * WARNING: This uses internal data binding classes. This enhancement described
 * in https://bugs.eclipse.org/bugs/show_bug.cgi?id=285307 would allow to use
 * official API instead of this class.
 * 
 * @author Ralf Ebert <info@ralfebert.de>
 */
@SuppressWarnings("restriction")
public class PropertyValue implements IValue {

  private final Object[] properties;

  /**
   * Creates a PropertyValue to access the bean property referred by
   * propertyName.
   */
  public PropertyValue(String propertyName) {
    properties = split(propertyName);

  }

  private static Object[] split(String propertyName) {
    if (propertyName.indexOf('.') == -1) {
      return new Object[] { propertyName };
    }
    List<String> propertyNames = new ArrayList<String>();
    int index;
    while ((index = propertyName.indexOf('.')) != -1) {
      propertyNames.add(propertyName.substring(0, index));
      propertyName = propertyName.substring(index + 1);
    }
    propertyNames.add(propertyName);
    return propertyNames.toArray(new Object[propertyNames.size()]);
  }

  /**
   * Returns the property value referred by object."propertyName"
   */
  @Override
  public Object getValue(Object object) {
    Object currentObject = object;
    for (int i = 0; i < properties.length; i++) {
      if (currentObject == null) {
        return null;
      }

      if (properties[i] instanceof String) {
        properties[i] = BeanPropertyHelper.getPropertyDescriptor(currentObject.getClass(), (String) properties[i]);
      }

      if (properties[i] instanceof PropertyDescriptor) {
        currentObject = BeanPropertyHelper.readProperty(currentObject, (PropertyDescriptor) properties[i]);
      } else {
        throw new RuntimeException("Invalid property: " + properties[i]);
      }

    }

    return currentObject;
  }

  /**
   * Sets the property value referred by object."propertyName" to value
   */
  @Override
  public void setValue(Object object, Object value) {
    Object currentObject = object;
    for (int i = 0; i < properties.length; i++) {
      if (currentObject == null) {
        throw new RuntimeException("Value cannot be set because of null value in nested property!");
      }

      if (properties[i] instanceof String) {
        properties[i] = BeanPropertyHelper.getPropertyDescriptor(currentObject.getClass(), (String) properties[i]);
      }

      if (properties[i] instanceof PropertyDescriptor) {
        boolean lastProperty = i == properties.length - 1;
        if (lastProperty) {
          BeanPropertyHelper.writeProperty(currentObject, (PropertyDescriptor) properties[i], value);
        } else {
          currentObject = BeanPropertyHelper.readProperty(currentObject, (PropertyDescriptor) properties[i]);
        }
      } else {
        throw new RuntimeException("Invalid property: " + properties[i]);
      }

    }
  }
}