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/*******************************************************************************
* Copyright (c) 2000, 2015 IBM Corporation and others.
*
* This program and the accompanying materials
* are made available under the terms of the Eclipse Public License 2.0
* which accompanies this distribution, and is available at
* https://www.eclipse.org/legal/epl-2.0/
*
* SPDX-License-Identifier: EPL-2.0
*
* Contributors:
* IBM Corporation - initial API and implementation
*******************************************************************************/
package org.eclipse.ui;
import org.w3c.dom.DOMException;
/**
* 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:
* </p>
* <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>
* 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 that doesn't start
* with a number. eg: [A-Za-z][A-Za-z0-9]* Using '.' is unsupported. However,
* the value of <code>TAG_ID</code> is reserved for internal use.
* </p>
* <p>
* The default implementation can throw a {@link DOMException} for createChild
* and put operations. See {@link XMLMemento}.
* </p>
* <p>
* This interface is not intended to be implemented or extended by clients.
* </p>
*
* @see IPersistableElement
* @see IElementFactory
* @see XMLMemento
* @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()
*/
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
*/
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
*/
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. May return <code>null</code> .
*/
IMemento getChild(String type);
/**
* Returns all children of this node.
*
* @return an array of children of this node. This will not be
* <code>null</code>. If there are no children, an array of length zero
* will be returned.
* @since 3.8
*/
IMemento[] getChildren();
/**
* Returns all children with the given type id.
*
* @param type the type id
* @return an array of children with the given type. This will not be
* <code>null</code>. If there are no keys, an array of length zero will
* be returned.
*/
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
*/
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
*/
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)
*/
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
*/
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
*/
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
*/
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
*/
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
*/
String[] getAttributeKeys();
/**
* Sets the value of the given key to the given floating point number.
*
* @param key the key
* @param value the value
*/
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
*/
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.
*/
void putMemento(IMemento memento);
/**
* Sets the value of the given key to the given string.
*
* @param key the key
* @param value the value
*/
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
*/
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
*/
void putTextData(String data);
}
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