diva.gui

Interface StoragePolicy

All Known Implementing Classes:

AbstractStoragePolicy, BasicStoragePolicy, DefaultStoragePolicy

public interface StoragePolicy

StoragePolicy captures the notion of how an application deals with persistent storage. For example, suppose a user selects the Close entry on a menu. The application typically needs to check whether the document has been edited, and if so, it needs to decide what to do about it. Two choices are:

1. Prompt the user asking whether to save the document first.
2. Save it anyway.
3. Save it but checkpoint the current state of the document so it can be undone later.
4. Sing "Daisy"

Each of these is an example of a storage policy. Because different applications may need different policies, yet some applications will use the same policies as other application, the concept of a storage policy has been reified into this interface and a set of implementing classes.

Version:

$Id: StoragePolicy.java 38798 2005-07-08 20:00:01Z cxh $

Author:

John Reekie

Method Summary

Modifier and Type	Method and Description
boolean	close(Document d) Close the document.
Document	open(Application app) Open a new document.
Document	open(java.io.File file, Application app) Open a file and create a new document.
Document	open(java.net.URL url, Application app) Open a URL and create a new document.
boolean	save(Document d) Save the document.
boolean	saveAs(Document d) Save the document to a user-specified location.

Method Detail

close

boolean close(Document d)

Close the document. Depending on the policy, this method will probably check whether the document has been edited and annoy the user with dialog boxes. If the document is null, do nothing. Return true if the document closed, otherwise false.

open

Document open(Application app)

Open a new document. This method will generally prompt the user for a location to open. If a new Document is created, return it, otherwise return null. (Note that if an existing document is re-opened, null is still returned.)

open

Document open(java.io.File file,
              Application app)

Open a file and create a new document. Depending on the policy, this method may choose to check whether the file has already been opened, and use the existing data, open a read-only view, etc. If it does open the file, it will use the passed DocumentFactory to do so. If a new Document is created, return it, otherwise return null. (Note that if an existing document is re-opened, null is still returned.)

open

Document open(java.net.URL url,
              Application app)

Open a URL and create a new document. Depending on the policy, this method may choose to check whether the URL has already been opened, and use the existing data, etc. If it does open the file, it will use the passed DocumentFactory to do so. If a new Document is created, return it, otherwise return null. (Note that if an existing document is re-opened, null is still returned.)

save

boolean save(Document d)

Save the document. Most policies will just save the file if it is possible to do so, but different policies may take different action of the file is write-protected (for example). Do nothing if the document is null. Return true if the file saved, otherwise false.

saveAs

boolean saveAs(Document d)

Save the document to a user-specified location. Depending on the policy, this may prompt the user for the file or URL location, and may or may not change the file or URL of the document to the new location. Do nothing if the document is null. Return true if the file saved, otherwise false.