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/*
Wotonomy: OpenStep design patterns for pure Java applications.
Copyright (C) 2000 Blacksmith, Inc.
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, see http://www.gnu.org
*/
package net.wotonomy.web;
/**
* A pure java implementation of WOAssociation. <br><br>
*
* A WOAssociation represents the mapping of a property on a
* WOComponent to a property on a WOAssociation. For example: <br><br>
*
* MyAssociation: WOString { value = currentCustomer.location.city }; <br><br>
*
* This example represents a WOAssociation between the value field
* on a WOString element and the city property of the location property
* of the currentCustomer property of a WOComponent. <br><br>
*
* To resolve values, a property accessor method will be used in
* preference to a public field, if both exist. Any null value
* in the path will produce null. <br><br>
*
* A mapping represented in quotation marks: { value = "This is a test." }
* is considered a constant value.
*
* @author michael@mpowers.net
* @author $Author: cgruber $
* @version $Revision: 893 $
*/
public class WOAssociation implements java.io.Serializable
{
protected Object value;
protected String path;
/**
* The default constructor. The static factory methods should
* be used to create instances of WOAssociation.
*/
protected WOAssociation ()
{
value = null;
path = null;
}
/**
* Creates a WOAssociation that maps to a constant value.
*/
public static WOAssociation associationWithValue (Object anObject)
{
WOAssociation result = new WOAssociation();
result.value = anObject;
return result;
}
/**
* Creates a WOAssociation that maps to the specified key path.
* If the path is null, the association will map to null.
* Throws an exception if the property cannot be resolved.
*/
public static WOAssociation associationWithKeyPath (String aString)
{
WOAssociation result = new WOAssociation();
result.path = aString;
return result;
}
/**
* Returns the value for this association's key path in the
* specified component, or null if any value in the path is
* null or if the key path is null.
*/
public Object valueInComponent (WOComponent aComponent)
{
if ( aComponent == null ) return null;
if ( value != null ) return value;
if ( path != null ) return aComponent.valueForKey( path );
throw new RuntimeException(
"WOAssociation: neither value nor path specified!" );
}
/**
* Sets the property in the specified component to the specified value.
* Throws an exception if the property cannot be resolved.
*/
public void setValue (Object aValue, WOComponent aComponent)
{
if ( path != null )
{
aComponent.takeValueForKey( aValue, path );
return;
}
throw new RuntimeException(
"WOAssociation: tried to set value but no path was specified!" );
}
/**
* Returns true if this association is writable; that is,
* returns true if this association is not constant.
*/
public boolean isValueSettable ()
{
return ( path != null );
}
/**
* Returns true if this association is constant
* and therefore read-only.
*/
public boolean isValueConstant ()
{
return ( path == null );
}
/**
* For debugging purposes.
*/
public String toString()
{
if ( path != null )
{
return "[WOAssociation:" + path + "]";
}
return "[WOAssociation:\"" + value + "\"]";
}
}
/*
* $Log$
* Revision 1.1 2006/02/16 13:22:22 cgruber
* Check in all sources in eclipse-friendly maven-enabled packages.
*
* Revision 1.6 2003/01/24 20:13:22 mpowers
* Now accepting immutable NSDictionary in constructor, not Map.
*
* Revision 1.5 2003/01/17 22:55:08 mpowers
* Straighted out the parent binding issue (I think).
* Fixes for woextensions compatibility.
*
* Revision 1.3 2003/01/15 19:50:49 mpowers
* Fixed issues with WOSession and Serializable.
* Can now persist sessions between classloaders (hot swap of class impls).
*
* Revision 1.2 2003/01/14 15:51:48 mpowers
* Removed value() method from WOAssociaton.
*
* Revision 1.1.1.1 2000/12/21 15:52:50 mpowers
* Contributing wotonomy.
*
* Revision 1.3 2000/12/20 16:25:49 michael
* Added log to all files.
*
*
*/
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