/*******************************************************************************
* Copyright (c) 2000, 2007 IBM Corporation 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:
* IBM Corporation - initial API and implementation
*******************************************************************************/
package org.eclipse.ui;
/**
* 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
* @noimplement This interface is not intended to be implemented by clients.
*/
public interface IMemento {
/**
* Special reserved key used to store the memento id
* (value <code>"IMemento.internal.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 an array 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 type for this memento.
*
* @return the memento type
* @see #createChild(java.lang.String)
* @see #createChild(java.lang.String,java.lang.String)
* @since 3.4
*/
public String getType();
/**
* Returns the id for this memento.
*
* @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
*/
public String getString(String key);
/**
* Returns the boolean value of the given key.
*
* @param key the key
* @return the value, or <code>null</code> if the key was not found
* @since 3.4
*/
public Boolean getBoolean(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();
/**
* Returns an array of all the attribute keys of the memento. This will not
* be <code>null</code>. If there are no keys, an array of length zero will
* be returned.
* @return an array with all the attribute keys of the memento
* @since 3.4
*/
public String[] getAttributeKeys();
/**
* 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 value of the given key to the given boolean value.
*
* @param key the key
* @param value the value
* @since 3.4
*/
public void putBoolean(String key, boolean 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);
}