Dear Wiki user, You have subscribed to a wiki page or wiki category on "Struts Wiki" for change notification.
The following page has been changed by MichaelJouravlev: http://wiki.apache.org/struts/StrutsCatalogDoUndoRedo The comment on the change is: orpahed; nothing more than a linked list. ------------------------------------------------------------------------------ - StrutsCatalog: '''Provide a Do, Undo, Redo command pattern solution that can assist a workflow application.''' + deleted - This is simple. Here are the basic classes and then I will give the application itself, which is fairly straightforward. - - {{{ - // COMMAND CLASS - public interface Command { - public void doCommand(); - public void undoCommand(); - } - - // Do, Undo, and Redo COMMANDS - public interface Do extends Command {} - - public final class Undo implements Command { - public void doCommand() { return; } - public void undoCommand() { return; } - } - - public final class Redo implements Command { - public void doCommand() { return; } - public void undoCommand() { return; } - } - }}} - - The following is the application class: - - {{{ - public class UndoableList { - private int maxHistory = 100; - private LinkedList history = new LinkedList(); - private LinkedList redoList = new LinkedList(); - - private UndoableList() { - } - - public static UndoableList getInstance() { - return new UndoableList(); - } - - public void setMaxHistory(int maxHistory) { - this.maxHistory = maxHistory; - } - - public void invoke(Command command) { - if (command instanceof Undo) { undoCommand(); return; } - if (command instanceof Redo) { redoCommand(); return; } - - if (command instanceof Do) { - command.doCommand(); - addToHistory(command); - } else { - history.clear(); - } - - if (redoList.size() > 0) { - redoList.clear(); - } - } - - private void undoCommand() { - if (history.size() > 0) { - Command undoCommand = (Command)history.removeFirst(); - undoCommand.undoCommand(); - redoList.addFirst(undoCommand); - } - } - - private void redoCommand() { - if (redoList.size() > 0) { - Command redoCommand = (Command)redoList.removeFirst(); - redoCommand.doCommand(); - history.addFirst(redoCommand); - } - } - - private void addToHistory(Command command) { - history.addFirst(command); - if (history.size() > maxHistory) { - history.removeLast(); - } - } - } - }}} - - You can clearly add to this or change this in a myriad of ways. - - Enjoy! - - Michael !McGrady - - --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
