path: root/src/com/itmill/toolkit/data/util/ObjectProperty.java

/* *************************************************************************
 
                               IT Mill Toolkit 

               Development of Browser User Interfaces Made Easy

                    Copyright (C) 2000-2006 IT Mill Ltd
                     
   *************************************************************************

   This product is distributed under commercial license that can be found
   from the product package on license.pdf. Use of this product might 
   require purchasing a commercial license from IT Mill Ltd. For guidelines 
   on usage, see licensing-guidelines.html

   *************************************************************************
   
   For more information, contact:
   
   IT Mill Ltd                           phone: +358 2 4802 7180
   Ruukinkatu 2-4                        fax:   +358 2 4802 7181
   20540, Turku                          email:  info@itmill.com
   Finland                               company www: www.itmill.com
   
   Primary source for information and releases: www.itmill.com

   ********************************************************************** */

package com.itmill.toolkit.data.util;

import com.itmill.toolkit.data.Property;

import java.lang.reflect.Constructor;
import java.util.LinkedList;

/** A simple data object containing one typed value. This class is a
 * straightforward implementation of the the
 * {@link com.itmill.toolkit.data.Property} interface.
 *
 * @author IT Mill Ltd.
 * @version @VERSION@
 * @since 3.0
 */
public class ObjectProperty implements Property, Property.ValueChangeNotifier,
Property.ReadOnlyStatusChangeNotifier {
  
  	/** A boolean value storing the Property's read-only status
  	 * information.
  	 */  
    private boolean readOnly = false;
  
  	/** The value contained by the Property. */  
    private Object value;
  
  	/** Data type of the Property's value */  
    private Class type;
  
  	/** Internal list of registered value change listeners. */  
    private LinkedList valueChangeListeners = null;
  
  	/** Internal list of registered read-only status change listeners. */
    private LinkedList readOnlyStatusChangeListeners = null;
    
    /** Creates a new instance of ObjectProperty with the given value.
     * The type of the property is automatically initialized to be
     * the type of the given value.
     *
     * @param value Initial value of the Property
     */
    public ObjectProperty(Object value) {
        this(value,value.getClass());
    }
    
    /** Creates a new instance of ObjectProperty with the given value and
     * type.
     * 
     * @param value Initial value of the Property
     * @param type The type of the value. The value must be assignable to
     * given type
     */
    public ObjectProperty(Object value, Class type) {
        
        // Set the values
        this.type = type;
        setValue(value);
    }
    
    /** Creates a new instance of ObjectProperty with the given value, type
     * and read-only mode status.
     * 
     * @param value Initial value of the property.
     * @param type The type of the value. <code>value</code> must be
     * assignable to this type.
     * @param readOnly Sets the read-only mode.
     */
    public ObjectProperty(Object value, Class type, boolean readOnly) {
        this(value,type);
        setReadOnly(readOnly);
    }
    
    /** Returns the type of the ObjectProperty. The methods
     * <code>getValue</code> and <code>setValue</code> must be compatible
     * with this type: one must be able to safely cast the value returned
     * from <code>getValue</code> to the given type and pass any variable
     * assignable to this type as an argument to <code>setValue</code>.
     * 
     * @return type of the Property
     */
    public final Class getType() {
        return type;
    }
    
    /** Gets the value stored in the Property.
     * 
     * @return the value stored in the Property
     */
    public Object getValue() {
        return value;
    }
    
    /** Returns the value of the ObjectProperty in human readable textual
     * format. The return value should be assignable to the
     * <code>setValue</code> method if the Property is not in read-only
     * mode.
     * 
     * @return <code>String</code> representation of the value stored in the
     * ObjectProperty
     */
    public String toString() {
    	Object value = getValue();
    	if (value != null) 
        	return value.toString();
        else 
        	return null;
    }
    
    /** Tests if the Property is in read-only mode. In read-only mode calls
     * to the method <code>setValue</code> will throw
     * <code>ReadOnlyException</code>s and will not modify the value of the
     * Property.
     *
     * @return <code>true</code> if the Property is in read-only mode,
     * <code>false</code> if it's not
     */
    public boolean isReadOnly() {
        return readOnly;
    }
    
    /** Sets the Property's read-only mode to the specified status.
     * 
     * @param newStatus new read-only status of the Property
     */	
    public void setReadOnly(boolean newStatus) {
    	if (newStatus != readOnly) {
    		readOnly = newStatus;
    		fireReadOnlyStatusChange();
    	}
    }
    
    /** Set the value of the property. This method supports setting from
     * <code>String</code>s if either <code>String</code> is directly
     * assignable to property type, or the type class contains a string
     * constructor.
     *
     * @param newValue New value of the property.
     * @throws <code>Property.ReadOnlyException</code> if the object is in
     * read-only mode
     * @throws <code>Property.ConversionException</code> if
     * <code>newValue</code> can't be converted into the Property's native
     * type directly or through <code>String</code>
     */
    public void setValue(Object newValue)
    throws Property.ReadOnlyException, Property.ConversionException {
        
        // Check the mode
        if (isReadOnly()) throw new Property.ReadOnlyException();
        
        // Try to assign the compatible value directly
        if (newValue == null || type.isAssignableFrom(newValue.getClass()))
            value = newValue;
        
        // Otherwise try to convert the value trough string constructor
        else try {
            
            // Get the string constructor
            Constructor constr =
            getType().getConstructor(new Class[] { String.class });
            
            // Create new object from the string
            value = constr.newInstance(new Object[] {newValue.toString()});
            
        } catch (java.lang.Exception e) {
            throw new Property.ConversionException(e);
        }

        fireValueChange();
    }

    /* Events *************************************************************** */
    
    /** An <code>Event</code> object specifying the ObjectProperty whose value
     * has changed.
     * @author IT Mill Ltd.
     * @version @VERSION@
     * @since 3.0
     */
    private class ValueChangeEvent extends java.util.EventObject
    implements Property.ValueChangeEvent {
        
        /**
         * Serial generated by eclipse.
         */
        private static final long serialVersionUID = 3256718468479725873L;

        /** Constructs a new value change event for this object.
         * 
         * @param source source object of the event
         */
        protected ValueChangeEvent(ObjectProperty source) {
            super(source);
        }
        
        /** Gets the Property whose read-only state has changed.
         * 
         * @return source Property of the event.
         */
        public Property getProperty() {
            return (Property) getSource();
        }
    }
    
   /** An <code>Event</code> object specifying the Property whose read-only
     * status has been changed.
     * @author IT Mill Ltd.
     * @version @VERSION@
     * @since 3.0
     */
	private class ReadOnlyStatusChangeEvent extends java.util.EventObject
    implements Property.ReadOnlyStatusChangeEvent {
        
        /**
         * Serial generated by eclipse.
         */
        private static final long serialVersionUID = 3907208273529616696L;

        /** Constructs a new read-only status change event for this object.
         * 
         * @param source source object of the event
         */
        protected ReadOnlyStatusChangeEvent(ObjectProperty source) {
            super(source);
        }
        
        /** Gets the Property whose read-only state has changed.
         * 
         * @return source Property of the event.
         */
        public Property getProperty() {
            return (Property) getSource();
        }
    }
    
    /** Remove a previously registered value change listener.
     * 
     * @param listener listener to be removed
     */
    public void removeListener(Property.ValueChangeListener listener) {
        if (valueChangeListeners != null) 
            valueChangeListeners.remove(listener);
    }
    
    /** Registers a new value change listener for this ObjectProperty.
     * 
     * @param listener the new Listener to be registered
     */
    public void addListener(Property.ValueChangeListener listener) {
        if (valueChangeListeners == null) 
            valueChangeListeners = new LinkedList();
        valueChangeListeners.add(listener);
    }
    
    /** Registers a new read-only status change listener for this Property.
     * 
     * @param listener the new Listener to be registered
     */
    public void addListener(Property.ReadOnlyStatusChangeListener listener) {
        if (readOnlyStatusChangeListeners == null)
            readOnlyStatusChangeListeners = new LinkedList();
        readOnlyStatusChangeListeners.add(listener);
    }
    
    /** Remove a previously registered read-only status change listener.
     * 
     * @param listener listener to be removed
     */
    public void removeListener(Property.ReadOnlyStatusChangeListener listener) {
        if (readOnlyStatusChangeListeners != null)
            readOnlyStatusChangeListeners.remove(listener);
    }
    
    /** Send a value change event to all registered listeners.
     */
    private void fireValueChange() {
        if (valueChangeListeners != null) {
            Object[] l = valueChangeListeners.toArray();
            Property.ValueChangeEvent event =
            new ObjectProperty.ValueChangeEvent(this);
            for (int i=0; i<l.length; i++)
                ((Property.ValueChangeListener)l[i]).valueChange(event);
        }
    }

    /** Send a read only status change event to all registered listeners.
     */
    private void fireReadOnlyStatusChange() {
        if (readOnlyStatusChangeListeners != null) {
            Object[] l = readOnlyStatusChangeListeners.toArray();
            Property.ReadOnlyStatusChangeEvent event =
            new ObjectProperty.ReadOnlyStatusChangeEvent(this);
            for (int i=0; i<l.length; i++)
                ((Property.ReadOnlyStatusChangeListener)l[i]).
                readOnlyStatusChange(event);
        }
    }
}