| /* Element.java -- Base class for object tree elements. |
| Copyright (C) 2005 Free Software Foundation, Inc. |
| |
| This file is part of GNU Classpath. |
| |
| GNU Classpath is free software; you can redistribute it and/or modify |
| it under the terms of the GNU General Public License as published by |
| the Free Software Foundation; either version 2, or (at your option) |
| any later version. |
| |
| GNU Classpath 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 |
| General Public License for more details. |
| |
| You should have received a copy of the GNU General Public License |
| along with GNU Classpath; see the file COPYING. If not, write to the |
| Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA |
| 02110-1301 USA. |
| |
| Linking this library statically or dynamically with other modules is |
| making a combined work based on this library. Thus, the terms and |
| conditions of the GNU General Public License cover the whole |
| combination. |
| |
| As a special exception, the copyright holders of this library give you |
| permission to link this library with independent modules to produce an |
| executable, regardless of the license terms of these independent |
| modules, and to copy and distribute the resulting executable under |
| terms of your choice, provided that you also meet, for each linked |
| independent module, the terms and conditions of the license of that |
| module. An independent module is a module which is not derived from |
| or based on this library. If you modify this library, you may extend |
| this exception to your version of the library, but you are not |
| obligated to do so. If you do not wish to do so, delete this |
| exception statement from your version. */ |
| |
| |
| package gnu.java.beans.encoder.elements; |
| |
| import java.util.Iterator; |
| import java.util.LinkedList; |
| |
| import gnu.java.beans.encoder.ObjectId; |
| import gnu.java.beans.encoder.Writer; |
| |
| /** <code>Element</code> is the base class for the object tree elements. |
| * |
| * <p>It provides the neccessary infrastructure every element subclass |
| * needs in order to interact with the {@link gnu.java.beans.encoder.Root} |
| * class.</p> |
| * |
| * @author Robert Schuster (robertschuster@fsfe.org) |
| */ |
| public abstract class Element |
| { |
| /** |
| * Stores the child elements. |
| */ |
| private LinkedList children = new LinkedList(); |
| |
| /** |
| * An optional ObjectId instance which is needed for certain subclasses |
| * only. |
| */ |
| private ObjectId objectId; |
| |
| /** Sets an {@link gnu.java.beans.encoder.ObjectId} instance in this |
| * <code>Element</code>. |
| * |
| * <p>This can only be done once.</p> |
| * |
| * @param objectId An ObjectId instance. |
| */ |
| public final void initId(ObjectId objectId) |
| { |
| assert (this.objectId == null); |
| assert (objectId != null); |
| |
| this.objectId = objectId; |
| } |
| |
| /** Adds a child element to this <code>Element</code>. |
| * |
| * @param elem The new child. |
| */ |
| public final void addChild(Element elem) |
| { |
| children.add(elem); |
| } |
| |
| /** Removes the child element added last. |
| */ |
| public final void removeLast() |
| { |
| children.removeLast(); |
| } |
| |
| /** Provides access to the child elements via an iterator. |
| * |
| * @return An iterator for the child elements. |
| */ |
| public final Iterator iterator(){ |
| return children.iterator(); |
| } |
| |
| /** Clears all the stored child elements. |
| * |
| */ |
| public final void clear() |
| { |
| children.clear(); |
| } |
| |
| /** Returns whether this element contains child elements. |
| * |
| * <p>This method is useful to decide which formatting variant |
| * for the XML element can be chosen.</p> |
| * |
| * @return Whether the element has child elements. |
| */ |
| public final boolean isEmpty() |
| { |
| return children.isEmpty(); |
| } |
| |
| /** Retrieves the element's {@link gnu.java.beans.encoder.ObjectId} instance |
| * if it has one. |
| * |
| * @return The ObjectId instance or <code>null</code>. |
| */ |
| public final ObjectId getId() |
| { |
| return objectId; |
| } |
| |
| /** Writes the opening XML tag. |
| * |
| * @param writer The writer to be used for XML writing. |
| */ |
| public abstract void writeStart(Writer writer); |
| |
| /** Writes the closing XML tag. |
| * |
| * <p>By default this does <code>writer.writeEnd(children.isEmpty())</code>. |
| * Override if neccessary, for example when using the |
| * {@link gnu.java.beans.encoder.Writer#writeNoChildren}</code> method |
| * variants. |
| * |
| * @param writer The writer to be used for XML writing. |
| */ |
| public void writeEnd(Writer writer) |
| { |
| writer.writeEnd(children.isEmpty()); |
| } |
| |
| } |