Property.java

/*
 * Copyright (c) 2011-2013, 2015 Eike Stepper (Berlin, Germany) and others.
 * 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:
 *    Eike Stepper - initial API and implementation
 *    Christian W. Damus (CEA LIST) - bug 418452
 */
package org.eclipse.net4j.util.properties;

import org.eclipse.net4j.internal.util.bundle.OM;
import org.eclipse.net4j.util.ObjectUtil;
import org.eclipse.net4j.util.lifecycle.LifecycleException;
import org.eclipse.net4j.util.lifecycle.LifecycleUtil;

/**
 * Describes a property of a receiver object and extracts its value.
 *
 * @author Eike Stepper
 * @since 3.2
 */
public abstract class Property<RECEIVER>
{
  private final String name;

  private final String label;

  private final String description;

  private final String category;

  public Property(String name, String label, String description, String category)
  {
    this.name = name;
    this.label = label;
    this.description = description;
    this.category = category;
  }

  public Property(String name, String label, String description)
  {
    this(name, label, description, null);
  }

  public Property(String name)
  {
    this(name, null, null);
  }

  public final String getName()
  {
    return name;
  }

  public final String getLabel()
  {
    return label;
  }

  public final String getDescription()
  {
    return description;
  }

  public final String getCategory()
  {
    return category;
  }

  public boolean testValue(RECEIVER receiver, Object[] args, Object expectedValue)
  {
    Object value = getValue(receiver);
    if (value instanceof Boolean && expectedValue == null)
    {
      // Per the Expressions extension point spec, the 'value' attribute
      // is optional for boolean-valued properties, in which case its
      // default is true
      expectedValue = Boolean.TRUE;
    }

    return ObjectUtil.equals(value, expectedValue);
  }

  public final Object getValue(RECEIVER receiver)
  {
    try
    {
      Object value = eval(receiver);
      if (value == null)
      {
        return value;
      }

      Class<? extends Object> c = value.getClass();
      if (c == Boolean.class)
      {
        return value;
      }

      if (c == Boolean.class)
      {
        return value;
      }

      if (c == Character.class)
      {
        return value;
      }

      if (c == Byte.class)
      {
        return value;
      }

      if (c == Short.class)
      {
        return value;
      }

      if (c == Integer.class)
      {
        return value;
      }

      if (c == Long.class)
      {
        return value;
      }

      if (c == Float.class)
      {
        return value;
      }

      if (c == Double.class)
      {
        return value;
      }

      return value.toString();
    }
    catch (LifecycleException ex)
    {
      //$FALL-THROUGH$
    }
    catch (Throwable ex)
    {
      if (LifecycleUtil.isActive(receiver))
      {
        OM.LOG.error(ex);
      }
    }

    return null;
  }

  /**
   * Returns the receiver's value for this property, either a {@link String} or a boxed primitive type. Return values of
   * all other types are converted with {@link #toString()} in {@link #eval(Object)}.
   */
  protected abstract Object eval(RECEIVER receiver);
}