bundles/org.eclipse.ui/Eclipse UI/org/eclipse/ui/IMemento.java

package org.eclipse.ui;

/**********************************************************************
Copyright (c) 2000, 2002 IBM Corp. and others.
All rights reserved.   This program and the accompanying materials
are made available under the terms of the Common Public License v0.5
which accompanies this distribution, and is available at
http://www.eclipse.org/legal/cpl-v05.html
 
Contributors:
**********************************************************************/
 
/**
 * Interface to a memento used for saving the important state of an object
 * in a form that can be persisted in the file system.
 * <p>
 * Mementos were designed with the following requirements in mind:
 * <ol>
 *  <li>Certain objects need to be saved and restored across platform sessions.
 *    </li>
 *  <li>When an object is restored, an appropriate class for an object might not
 *    be available. It must be possible to skip an object in this case.</li>
 *  <li>When an object is restored, the appropriate class for the object may be
 *    different from the one when the object was originally saved. If so, the
 *    new class should still be able to read the old form of the data.</li>
 * </ol>
 * </p>
 * <p>
 * Mementos meet these requirements by providing support for storing a
 * mapping of arbitrary string keys to primitive values, and by allowing
 * mementos to have other mementos as children (arranged into a tree).
 * A robust external storage format based on XML is used.
 * </p><p>
 * The key for an attribute may be any alpha numeric value.  However, the
 * value of <code>TAG_ID</code> is reserved for internal use.
 * </p><p>
 * This interface is not intended to be implemented or extended by clients.
 * </p>
 *
 * @see IPersistableElement
 * @see IElementFactory
 */ 
public interface IMemento {
	/**
	 * Special reserved key used to store the memento id 
	 * (value <code>"org.eclipse.ui.id"</code>).
	 *
	 * @see #getId
	 */
	public static final String TAG_ID = "IMemento.internal.id"; //$NON-NLS-1$
/**
 * Creates a new child of this memento with the given type.
 * <p>
 * The <code>getChild</code> and <code>getChildren</code> methods
 * are used to retrieve children of a given type.
 * </p>
 *
 * @param type the type
 * @return a new child memento
 * @see #getChild
 * @see #getChildren
 */
public IMemento createChild(String type);
/**
 * Creates a new child of this memento with the given type and id.
 * The id is stored in the child memento (using a special reserved
 * key, <code>TAG_ID</code>) and can be retrieved using <code>getId</code>.
 * <p>
 * The <code>getChild</code> and <code>getChildren</code> methods
 * are used to retrieve children of a given type.
 * </p>
 *
 * @param type the type
 * @param id the child id
 * @return a new child memento with the given type and id
 * @see #getId
 */
public IMemento createChild(String type, String id);
/**
 * Returns the first child with the given type id.
 *
 * @param type the type id
 * @return the first child with the given type
 */
public IMemento getChild(String type);
/**
 * Returns all children with the given type id.
 *
 * @param type the type id
 * @return the list of children with the given type
 */
public IMemento[] getChildren(String type);
/**
 * Returns the floating point value of the given key.
 *
 * @param key the key
 * @return the value, or <code>null</code> if the key was not found or was found
 *   but was not a floating point number
 */
public Float getFloat(String key);
/**
 * Returns the id for this memento.
 * <p>
 * [Issue: For consistency, rename to "getId".]
 * </p>
 *
 * @return the memento id, or <code>null</code> if none
 * @see #createChild(java.lang.String,java.lang.String)
 */
public String getID();
/**
 * Returns the integer value of the given key.
 *
 * @param key the key
 * @return the value, or <code>null</code> if the key was not found or was found
 *   but was not an integer
 */
public Integer getInteger(String key);
/**
 * Returns the string value of the given key.
 *
 * @param key the key
 * @return the value, or <code>null</code> if the key was not found or was found
 *  but was not an integer
 */
public String getString(String key);
/**
 * Returns the data of the Text node of the memento. Each memento is allowed
 * only one Text node.
 * 
 * @return the data of the Text node of the memento, or <code>null</code>
 * if the memento has no Text node.
 * @since 2.0
 */
public String getTextData();
/**
 * Sets the value of the given key to the given floating point number.
 *
 * @param key the key
 * @param value the value
 */
public void putFloat(String key, float value);
/**
 * Sets the value of the given key to the given integer.
 *
 * @param key the key
 * @param value the value
 */
public void putInteger(String key, int value);
/**
 * Copy the attributes and children from  <code>memento</code>
 * to the receiver.
 *
 * @param memento the IMemento to be copied.
 */
public void putMemento(IMemento memento);
/**
 * Sets the value of the given key to the given string.
 *
 * @param key the key
 * @param value the value
 */
public void putString(String key, String value);
/**
 * Sets the memento's Text node to contain the given data. Creates the Text node if
 * none exists. If a Text node does exist, it's current contents are replaced. 
 * Each memento is allowed only one text node.
 * 
 * @param data the data to be placed on the Text node
 * @since 2.0
 */
public void putTextData(String data);
}