com.yworks.yfiles.server.tiles.servlet
Class UndoServlet

java.lang.Object
  javax.servlet.GenericServlet
      javax.servlet.http.HttpServlet
          com.yworks.yfiles.server.tiles.servlet.BaseServlet
              com.yworks.yfiles.server.tiles.servlet.UndoServlet

All Implemented Interfaces:

Serializable, javax.servlet.Servlet, javax.servlet.ServletConfig

public class UndoServlet

extends BaseServlet

This servlet handles requests related to undo/redo.

Since undo/redo requires extra resources it is not enabled by default. This servlet handles requests for enabling and disabling undo/redo for a graph cached at the current session. ("setUndoRedoEnabled" and "isUndoRedoEnabled").

Even if undo/redo is enabled undo can only be performed, if there was at least one update to a graph after undo/redo was enabled for the graph. So there is a request for checking whether undo or redo is possible ("canUndoRedo").

Finally, this servlet handles the requests for performing an undo or redo operation ("undo", "redo").

The requests for performing the operations which actually change the state ("setUndoRedoEnabled", "undo" and "redo") have to be POST requests. The requests for performing a query operation ("isUndoRedoEnabled", "canUndoRedo") may be GET or POST requests.

If undo/redo is enabled for a graph then a standard Graph2DUndoManager is created and registered as the backup realizers handler at the graph. This manager is then used by all other operations. Subclasses may implement their undo management differently by redefining createUndoManager(y.view.Graph2D) and getUndoManager(y.view.Graph2D).

See Also:

Serialized Form

Field Summary

Fields inherited from class com.yworks.yfiles.server.tiles.servlet.BaseServlet

EDGE_DESCRIPTION_KEY, EDGE_URL_KEY, NODE_DESCRIPTION_KEY, NODE_URL_KEY

Constructor Summary

UndoServlet()

Method Summary

protected boolean	canRedo(Graph2D graph) Returns whether a redo can be performed for the given graph.
protected boolean	canUndo(Graph2D graph) Returns whether an undo can be performed for the given graph.
protected Graph2DUndoManager	createUndoManager(Graph2D graph) Creates and returns a new undo manager for the given graph.
protected Graph2DUndoManager	getUndoManager(Graph2D graph) Returns the undo manager for the given graph.
protected void	handleGetRequest(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) handles "isUndoRedoEnabled" and "canUndoRedo" requests.
protected void	handlePostRequest(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) handles "setUndoRedoEnabled", "undo" and "redo" requests.
protected boolean	isUndoRedoEnabled(Graph2D graph) Returns whether undo/redo is enabled for the given graph.
protected void	redo(Graph2D graph) reverts the last undo for the given graph.
protected void	setUndoRedoEnabled(Graph2D graph, boolean enabled) Sets whether undo/redo is enabled for the given graph.
protected void	undo(Graph2D graph) reverts the last change for the given graph.

Methods inherited from class com.yworks.yfiles.server.tiles.servlet.BaseServlet

addViewConfigurator, cachedGraphs, cacheGraph, doGet, doPost, getEdgeDescription, getEdgeURL, getForId, getGraph, getGraphBounds, getGraphContentBounds, getId, getId, getId, getId, getNodeDescription, getNodeURL, getReadWriteLock, getSessionMonitor, getViewConfigurators, getWriter, hasDescriptions, hasURLs, init, initialize, isUseJSONPrefixing, lookupId, lookupId, lookupId, lookupId, newGraph, readLock, registerLicense, removeViewConfigurator, setEdgeDescription, setEdgeURL, setNodeDescription, setNodeURL, uncacheGraph, unlockRead, unlockWrite, updateEdgePaths, validateIds, writeContentBounds, writeLock, writeWorldBounds

Methods inherited from class javax.servlet.http.HttpServlet

doDelete, doHead, doOptions, doPut, doTrace, getLastModified, service, service

Methods inherited from class javax.servlet.GenericServlet

destroy, getInitParameter, getInitParameterNames, getServletConfig, getServletContext, getServletInfo, getServletName, init, log, log

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

UndoServlet

public UndoServlet()

Method Detail

handlePostRequest

protected void handlePostRequest(javax.servlet.http.HttpServletRequest request,
                                 javax.servlet.http.HttpServletResponse response)
                          throws javax.servlet.ServletException,
                                 IOException

handles "setUndoRedoEnabled", "undo" and "redo" requests. The parameter "name" is mandatory for all requests. It is the symbolic name of the graph to be used.

This method detects the operation to perform, fetches the necessary parameters from the requests and the graph from the session and then calls one of the protected methods in this class which act on the graph like undo(y.view.Graph2D).

If the requests is neither "setUndoRedoEnabled", "undo" or "redo" then the method for handling GET requests is called. Thus a query operation ("isUndoRedoEnabled", "canUndoRedo") can also be initiated by a POST request.

Overrides:

handlePostRequest in class BaseServlet

Parameters:

request - the request

response - the response to write to

Throws:

javax.servlet.ServletException

IOException

handleGetRequest

protected void handleGetRequest(javax.servlet.http.HttpServletRequest request,
                                javax.servlet.http.HttpServletResponse response)
                         throws javax.servlet.ServletException,
                                IOException

handles "isUndoRedoEnabled" and "canUndoRedo" requests. The parameter "name" is mandatory for all requests. It is the symbolic name of the graph to be used. "canUndoRedo" returns an object in JSON format like the following.

 { "canUndo" : true, "canRedo" : false }
 

This method detects the operation to perform, fetches the necessary parameters from the requests and the graph from the session and then calls one of the protected methods in this class which act on the graph like canUndo(y.view.Graph2D).

Overrides:

handleGetRequest in class BaseServlet

Parameters:

request - the request

response - the response to write to

Throws:

javax.servlet.ServletException

IOException

isUndoRedoEnabled

protected boolean isUndoRedoEnabled(Graph2D graph)

Returns whether undo/redo is enabled for the given graph. This method checks whether an undo manager is available using getUndoManager(y.view.Graph2D).

Parameters:

graph - a graph

Returns:

whether undo/redo is enabled

setUndoRedoEnabled

protected void setUndoRedoEnabled(Graph2D graph,
                                  boolean enabled)

Sets whether undo/redo is enabled for the given graph. This method checks whether an undo manager is available using getUndoManager(y.view.Graph2D). This method creates an undo manager if necessary using createUndoManager(y.view.Graph2D).

Parameters:

graph - a graph

enabled - if true enable undo/redo, disable it otherwise

undo

protected void undo(Graph2D graph)

reverts the last change for the given graph. This method uses the undo manager returned by getUndoManager(y.view.Graph2D).

Parameters:

graph - a graph

redo

protected void redo(Graph2D graph)

reverts the last undo for the given graph. This method uses the undo manager returned by getUndoManager(y.view.Graph2D).

Parameters:

graph - a graph

canUndo

protected boolean canUndo(Graph2D graph)

Returns whether an undo can be performed for the given graph. This method uses the undo manager returned by getUndoManager(y.view.Graph2D).

Parameters:

graph - a graph

Returns:

whether an undo can be performed

canRedo

protected boolean canRedo(Graph2D graph)

Returns whether a redo can be performed for the given graph. This method uses the undo manager returned by getUndoManager(y.view.Graph2D).

Parameters:

graph - a graph

Returns:

whether a redo can be performed

createUndoManager

protected Graph2DUndoManager createUndoManager(Graph2D graph)

Creates and returns a new undo manager for the given graph.

Parameters:

graph - the graph

Returns:

an undo manager

See Also:

getUndoManager(y.view.Graph2D)

getUndoManager

protected Graph2DUndoManager getUndoManager(Graph2D graph)

Returns the undo manager for the given graph.

Parameters:

graph - a graph

Returns:

the undo manager or null

See Also:

createUndoManager(y.view.Graph2D)