de.saxsys.synchronizefx.core.metamodel.executors.lists

Class ListPropertyCommandFilter

java.lang.Object

de.saxsys.synchronizefx.core.metamodel.executors.lists.ListPropertyCommandFilter

All Implemented Interfaces:

ListPropertyCommandExecutor

public class ListPropertyCommandFilter
extends Object
implements ListPropertyCommandExecutor

Filters out commands from the command that are meant to be executed on other versions of a list property.

Each state of a list is identified by a version. A command that changes the list carries the version of the state on which is meant to be executed. If the current confirmed state of a list has a different version the command needs to be dropped. This is because there where other changes on the list which make it impossible to tell if the command can safely be applied or not.

When a list command was dropped, the sending peer can detect this and resends the adapted command (see ReparingListPropertyCommandExecutor). If the original list command carried a reference to an observable object, the object needs to be cached for some time on this side. This way it is ensured that the observable object is not garbage collected. The peer re-sending the command will only re-send the dropped list command, not the command that created the observable object.

Author:

Raik Bieniek

Constructor Summary

Constructors

Constructor and Description
ListPropertyCommandFilter(ListPropertyCommandExecutor executor, TemporaryReferenceKeeper referenceKeeper, ListPropertyMetaDataStore listVersions, WeakObjectRegistry objectRegistry, boolean useLocalVerision) Initializes an instance with all its dependencies.

Method Summary

Methods

Modifier and Type	Method and Description
void	execute(AddToList command) Filters the passed command and passes it to the executor when it is approved.
void	execute(RemoveFromList command) Filters the passed command and passes it to the executor when it is approved.
void	execute(ReplaceInList command) Filters the passed command and passes it to the executor when it is approved.

Methods inherited from class java.lang.Object

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

Constructor Detail

ListPropertyCommandFilter

public ListPropertyCommandFilter(ListPropertyCommandExecutor executor,
                         TemporaryReferenceKeeper referenceKeeper,
                         ListPropertyMetaDataStore listVersions,
                         WeakObjectRegistry objectRegistry,
                         boolean useLocalVerision)

Initializes an instance with all its dependencies.

Parameters:

executor - Used to execute commands that where not dropped.

referenceKeeper - Used to prevent observable objects of dropped commands from being garbage collected.

listVersions - Used to retrieve the current version of local list properties.

objectRegistry - Used to retrieve observable objects that need to be prevented from being garbage collected.

useLocalVerision - When true the local list version is used when deciding if commands need to be filtered out. When false, the approved list command version is used.

Method Detail

execute

public void execute(AddToList command)

Filters the passed command and passes it to the executor when it is approved.

Specified by:

execute in interface ListPropertyCommandExecutor

Parameters:

command - The command to filter

execute

public void execute(RemoveFromList command)

Filters the passed command and passes it to the executor when it is approved.

Specified by:

execute in interface ListPropertyCommandExecutor

Parameters:

command - The command to filter

execute

public void execute(ReplaceInList command)

Filters the passed command and passes it to the executor when it is approved.

Specified by:

execute in interface ListPropertyCommandExecutor

Parameters:

command - The command to filter