com.lf.vfslib.net

Class ClientPool

java.lang.Object

com.lf.vfslib.net.ClientPool

public class ClientPool
extends Object

Handles multiple network connections to be recycled.

Standard VFS lacks support for connection pooling. For every resolve a new connection over FTP, SFTP etc. is established. This is OK for single files being resolved but not suitable for FTP client applications. If a FTP or SFTP connection has been established once it is cached and re-used whenever an appropriate network file is being resolved.

This pool mechanism is appropriate for stateful protocols like FTP, FTPS, and SFTP (not for HTTP).

Helpful commands to monitor incoming FTP/SFTP connections under Linux: while (true) ; do clear;ps aux|grep vsftp ; sleep 1; done while (true) ; do clear;ps aux|grep sshd: ; sleep 1; done

Since:

1.6

Author:

Axel Schwolow

Constructor Summary

Constructors

Constructor and Description
ClientPool() Default constructor.

Method Summary

Modifier and Type	Method and Description
void	addClient(ClientWrapper client) Adds a new client for the pool, normally added by the provider client factories.
boolean	canRelease(Object id) Checks whether a factory shared object can be released or not.
void	cleanup(Object id) Perform optional cleanup tasks like closing network connections or disposing dialogs.
String	debugPrint() Convenience method to show the current client pool.
ClientWrapper	getFreeClient(String url) Provides an open client for the network, recycled from the pool if possible (convenience).
void	getRegisteredObjects() Provides the currently managed objects.
static ClientPool	getSharedInstance() Provides the shared instance of the factory implementation.
boolean	hasSharedInstance(Object id) Create the factory shared object, recycle if already existing.
void	release(Object id) Releases the given shared objects immediately (free clients here).
void	releaseByStrategy() Release managed shared objects according to the configured strategy (free clients here).
void	releaseForced() Releases all managed shared objects immediately (free clients here).
Object	request(Object id) Provides an open client for the network, recycled from the pool (same as getFreeClient()).
Object	set(Object id, Object obj) Sets an object for an existing managed object.
boolean	unlockClient(ClientWrapper client) Releases an occupied client so that it can be re-used.

Methods inherited from class java.lang.Object

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

Constructor Detail

ClientPool

public ClientPool()

Default constructor.

Since:

1.6

Method Detail

getSharedInstance

public static ClientPool getSharedInstance()

Provides the shared instance of the factory implementation.

Returns:

Shared instance of the factory

Since:

1.6

request

public Object request(Object id)

Provides an open client for the network, recycled from the pool (same as getFreeClient()).

Here, a free network client can be requested. If none is available the method returns null. The provided network client is locked here automatically and must be unlocked explicitely to be recycled. If it returns null you have to create a new client and set it here using addClient(). This is necessary since we do not have required parameters like file system options here.

Parameters:

id - The factory-unique identifier of the shared object (String here, unique URL)

Returns:

The shared object, null if none could be created (ClientWrapper here)

Since:

1.6

See Also:

getFreeClient(String)

getFreeClient

public ClientWrapper getFreeClient(String url)

Provides an open client for the network, recycled from the pool if possible (convenience).

Parameters:

url - The client URL including login, port etc.

Returns:

Open client, null if an error occurred

Throws:

NullPointerException - If parameters are null

Since:

1.6

addClient

public void addClient(ClientWrapper client)

Adds a new client for the pool, normally added by the provider client factories.

The new client is locked automatically here.

Parameters:

client - Client to be added

Throws:

NullPointerException - If parameters are null

Since:

1.6

unlockClient

public boolean unlockClient(ClientWrapper client)

Releases an occupied client so that it can be re-used.

Parameters:

client - Client to be released

Returns:

Released successfully?

Throws:

NullPointerException - If parameters are null

Since:

1.6

canRelease

public boolean canRelease(Object id)

Checks whether a factory shared object can be released or not.

Parameters:

id - The factory-unique identifier of the shared object

Returns:

Can the object be released according to the factories needs?

Since:

1.6

release

public void release(Object id)

Releases the given shared objects immediately (free clients here).

Parameters:

id - The factory-unique identifier of the shared object

Throws:

NullPointerException - If a parameter is null

Since:

1.6

releaseForced

public void releaseForced()

Releases all managed shared objects immediately (free clients here).

This functionality can be used in order to make as much of occupied memory as possible available again. Normally this method calls the various release() methods of the factory class and is used always if the application reaches a certain amount of consumed memory. In critical situations the application can use this method in order to keep it running or at least store the current configurations or data portions safely (panic mode).

Since:

1.6

releaseByStrategy

public void releaseByStrategy()

Release managed shared objects according to the configured strategy (free clients here).

For applications it may be useful to flush its caches but keep certain objects/resources untouched since they will be needed in the future or the recreation would be expensive (e.g. when contents must be loaded from a database or from the internet).

This method should be used by a periodically executed release task in order to release all shared objects with timeout strategy.

Since:

1.6

cleanup

public void cleanup(Object id)

Perform optional cleanup tasks like closing network connections or disposing dialogs.

Parameters:

id - The factory-unique identifier of the shared object

Since:

1.6

hasSharedInstance

public boolean hasSharedInstance(Object id)

Create the factory shared object, recycle if already existing.

Parameters:

id - The factory-unique identifier of the shared object

Returns:

Does a shared instance already exist?

Since:

1.6

getRegisteredObjects

public void getRegisteredObjects()

Provides the currently managed objects.

Since:

1.6

set

public Object set(Object id,
                  Object obj)

Sets an object for an existing managed object.

Parameters:

id - The factory-unique identifier of the shared object

obj - The new object

Returns:

The overwritten object, may be null

Throws:

NullPointerException - If a parameter is null

Since:

1.6

debugPrint

public String debugPrint()

Convenience method to show the current client pool.

Returns:

The text

Since:

1.6