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Eclipse Platform
Release 3.0

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org.eclipse.ui
Interface IMemento

All Known Implementing Classes:

XMLMemento

public interface IMemento

Interface to a memento used for saving the important state of an object in a form that can be persisted in the file system.

Mementos were designed with the following requirements in mind:

1. Certain objects need to be saved and restored across platform sessions.
2. 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.
3. 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.

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.

The key for an attribute may be any alpha numeric value. However, the value of TAG_ID is reserved for internal use.

This interface is not intended to be implemented or extended by clients.

See Also:

IPersistableElement, IElementFactory

Field Summary

static String

TAG_ID Special reserved key used to store the memento id (value "org.eclipse.ui.id").

Method Summary

IMemento	createChild(String type) Creates a new child of this memento with the given type.
IMemento	createChild(String type, String id) Creates a new child of this memento with the given type and id.
IMemento	getChild(String type) Returns the first child with the given type id.
IMemento[]	getChildren(String type) Returns all children with the given type id.
Float	getFloat(String key) Returns the floating point value of the given key.
String	getID() Returns the id for this memento.
Integer	getInteger(String key) Returns the integer value of the given key.
String	getString(String key) Returns the string value of the given key.
String	getTextData() Returns the data of the Text node of the memento.
void	putFloat(String key, float value) Sets the value of the given key to the given floating point number.
void	putInteger(String key, int value) Sets the value of the given key to the given integer.
void	putMemento(IMemento memento) Copy the attributes and children from memento to the receiver.
void	putString(String key, String value) Sets the value of the given key to the given string.
void	putTextData(String data) Sets the memento's Text node to contain the given data.

Field Detail

TAG_ID

public static final String TAG_ID

Special reserved key used to store the memento id (value "org.eclipse.ui.id").

See Also:

getID(), Constant Field Values

Method Detail

createChild

public IMemento createChild(String type)

Creates a new child of this memento with the given type.

The getChild and getChildren methods are used to retrieve children of a given type.

Parameters:

type - the type

Returns:

a new child memento

See Also:

getChild(java.lang.String), getChildren(java.lang.String)

createChild

public IMemento createChild(String type,
                            String id)

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, TAG_ID) and can be retrieved using getId.

The getChild and getChildren methods are used to retrieve children of a given type.

Parameters:

type - the type

id - the child id

Returns:

a new child memento with the given type and id

See Also:

getID()

getChild

public IMemento getChild(String type)

Returns the first child with the given type id.

Parameters:

type - the type id

Returns:

the first child with the given type

getChildren

public IMemento[] getChildren(String type)

Returns all children with the given type id.

Parameters:

type - the type id

Returns:

the list of children with the given type

getFloat

public Float getFloat(String key)

Returns the floating point value of the given key.

Parameters:

key - the key

Returns:

the value, or null if the key was not found or was found but was not a floating point number

getID

public String getID()

Returns the id for this memento.

Returns:

the memento id, or null if none

See Also:

createChild(java.lang.String,java.lang.String)

getInteger

public Integer getInteger(String key)

Returns the integer value of the given key.

Parameters:

key - the key

Returns:

the value, or null if the key was not found or was found but was not an integer

getString

public String getString(String key)

Returns the string value of the given key.

Parameters:

key - the key

Returns:

the value, or null if the key was not found

getTextData

public String getTextData()

Returns the data of the Text node of the memento. Each memento is allowed only one Text node.

Returns:

the data of the Text node of the memento, or null if the memento has no Text node.

Since:

2.0

putFloat

public void putFloat(String key,
                     float value)

Sets the value of the given key to the given floating point number.

Parameters:

key - the key

value - the value

putInteger

public void putInteger(String key,
                       int value)

Sets the value of the given key to the given integer.

Parameters:

key - the key

value - the value

putMemento

public void putMemento(IMemento memento)

Copy the attributes and children from memento to the receiver.

Parameters:

memento - the IMemento to be copied.

putString

public void putString(String key,
                      String value)

Sets the value of the given key to the given string.

Parameters:

key - the key

value - the value

putTextData

public void putTextData(String data)

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.

Parameters:

data - the data to be placed on the Text node

Since:

2.0