org.openide.loaders

Class FolderInstance

java.lang.Object

org.openide.util.Task

org.openide.loaders.FolderInstance

All Implemented Interfaces:

Runnable, InstanceCookie, Node.Cookie

Direct Known Subclasses:

FolderLookup

public abstract class FolderInstance
extends Task
implements InstanceCookie

Support class for creation of an object from the content of a DataObject.Container. It implements InstanceCookie, so it can be used as a cookie for a node or data object.

When created on a container and started by invoking run method, it scans its content (in a separate thread) and creates a list of instances from which the new instance of this object should be composed. The object automatically listens to changes of components in the container, and if some change occurs, it allows the subclass to create a new object.

Subclasses shall override the following methods:

1. FolderInstance.createInstance(InstanceCookie[]) (required): this method is called whenever the content has been changed. Its implementation shall build up the data structures and perform the actions required by this implementation.
2. The filter methods FolderInstance.acceptDataObject(DataObject), FolderInstance.acceptCookie(InstanceCookie), FolderInstance.acceptFolder(DataFolder) and FolderInstance.acceptContainer(DataObject.Container) (optional): the standard way is to override one or several of the latter methods. Overriding FolderInstance.acceptDataObject(DataObject) more deeply modifies the default behavior, because the default implementation of FolderInstance.acceptDataObject(DataObject) calls the other 3 filter methods. See the method documentation for details.
3. The InstanceCookie methods FolderInstance.instanceClass() (optional but recommended) to inform about the class implemented by the return value of FolderInstance.instanceCreate().
4. Advanced subclasses may need to override FolderInstance.postCreationTask(java.lang.Runnable) and/or FolderInstance.instanceForCookie(org.openide.loaders.DataObject, org.openide.cookies.InstanceCookie), but it is not common to need these.

Nested Class Summary

Nested classes/interfaces inherited from interface org.openide.cookies.InstanceCookie

InstanceCookie.Of

Field Summary

Fields

Modifier and Type	Field and Description
protected DataFolder	folder Folder to work with.

Fields inherited from class org.openide.util.Task

EMPTY

Constructor Summary

Constructors

Constructor and Description
FolderInstance(DataFolder df) Create new folder instance.
FolderInstance(DataObject.Container container) A new object that listens on changes in a container.

Method Summary

Modifier and Type	Method and Description
protected InstanceCookie	acceptContainer(DataObject.Container container) Allows subclasses to decide how they want to work with an object that implements a DataObject.Container.
protected InstanceCookie	acceptCookie(InstanceCookie cookie) Allows subclasses to decide whether they want to work with the specified InstanceCookie or not.
protected InstanceCookie	acceptDataObject(DataObject dob) Allows subclasses to decide whether they want to work with the specified DataObject or not.
protected InstanceCookie	acceptFolder(DataFolder df) Allows subclasses to decide how they want to work with a provided folder.
protected abstract Object	createInstance(InstanceCookie[] cookies) Notifies subclasses that the set of cookies for this folder has changed.
Class<?>	instanceClass() Returns the root class of all objects.
Object	instanceCreate() Creates instance.
void	instanceFinished() Wait for instance initialization to finish.
protected Object	instanceForCookie(DataObject obj, InstanceCookie cookie) Method that is called when a the folder instance really wants to create an object from provided cookie.
String	instanceName() The name of the class that we create.
protected Task	postCreationTask(Runnable run) Invokes the creation of objects in a "safe" thread.
void	recreate() Starts recreation of the instance in special thread.
void	run() Synchronously starts the creation of the instance.
String	toString()
void	waitFinished() Overrides the instance finished to deal with internal state correctly.

Methods inherited from class org.openide.util.Task

addTaskListener, isFinished, notifyFinished, notifyRunning, removeTaskListener, waitFinished

Methods inherited from class java.lang.Object

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

Field Detail

folder

protected DataFolder folder

Folder to work with. Non null only if a constructor with DataFolder is used to construct this object.

Constructor Detail

FolderInstance

public FolderInstance(DataFolder df)

Create new folder instance.

Parameters:

df - data folder to create instances from

FolderInstance

public FolderInstance(DataObject.Container container)

A new object that listens on changes in a container.

Parameters:

container - the object to associate with

Since:

1.11

Method Detail

instanceName

public String instanceName()

The name of the class that we create.

Specified by:

instanceName in interface InstanceCookie

Returns:

the name

instanceClass

public Class<?> instanceClass()
                       throws IOException,
                              ClassNotFoundException

Returns the root class of all objects. Supposed to be overriden in subclasses.

Specified by:

instanceClass in interface InstanceCookie

Returns:

Object.class

Throws:

IOException - an I/O error occured

ClassNotFoundException - the class has not been found

instanceCreate

public Object instanceCreate()
                      throws IOException,
                             ClassNotFoundException

Creates instance.

Specified by:

instanceCreate in interface InstanceCookie

Returns:

an object to work with

Throws:

IOException - an I/O error occured

ClassNotFoundException - the class has not been found

instanceFinished

public final void instanceFinished()

Wait for instance initialization to finish.

waitFinished

public void waitFinished()

Overrides the instance finished to deal with internal state correctly.

Overrides:

waitFinished in class Task

run

public void run()

Synchronously starts the creation of the instance.

Specified by:

run in interface Runnable

Overrides:

run in class Task

acceptDataObject

protected InstanceCookie acceptDataObject(DataObject dob)

Allows subclasses to decide whether they want to work with the specified DataObject or not.

The default implementation roughly performs the following steps:

1. if dob has an InstanceCookie FolderInstance.acceptCookie(InstanceCookie) is called on that cookie
2. if dob has a DataFolder cookie, FolderInstance.acceptFolder(DataFolder) is called on that folder
3. if dob has a DataObject.Container cookie, FolderInstance.acceptContainer(DataObject.Container) is called on that container

The first of the aforementioned steps which returns a non-null cookie and does not throw an exception determines the return value. If none of the steps succeeds, null is returned.

Parameters:

dob - a DataObject to test

Returns:

the cookie for the DataObject or null if it should not be used

acceptCookie

protected InstanceCookie acceptCookie(InstanceCookie cookie)
                               throws IOException,
                                      ClassNotFoundException

Allows subclasses to decide whether they want to work with the specified InstanceCookie or not.

The default implementation simply returns the same cookie, but subclasses may decide to return null or a different cookie.

Compare FolderInstance.acceptDataObject(DataObject) to learn when this method is called.

Parameters:

cookie - the instance cookie to test

Returns:

the cookie to use or null if this cookie should not be used

Throws:

IOException - if an I/O error occurred calling a cookie method

ClassNotFoundException - if a class is not found in a call to a cookie method

acceptFolder

protected InstanceCookie acceptFolder(DataFolder df)

Allows subclasses to decide how they want to work with a provided folder.

The default implementation simply calls FolderInstance.acceptContainer(DataObject.Container).

A common override of this method is to return a new FolderInstance based on the subfolder, permitting recursion.

Compare FolderInstance.acceptDataObject(DataObject) to learn when this method is called.

Parameters:

df - data folder to create cookie for

Returns:

the cookie for this folder or null if this folder should not be used

acceptContainer

protected InstanceCookie acceptContainer(DataObject.Container container)

Allows subclasses to decide how they want to work with an object that implements a DataObject.Container.

By default this returns null to indicated that subfolders (as well as DataShadows, etc.) should be ignored.

A common override of this method is to return a new FolderInstance based on the subfolder, permitting recursion.

Compare FolderInstance.acceptDataObject(DataObject) to learn when this method is called.

Parameters:

container - the container to accept or not

Returns:

cookie for this container or null if this object should be ignored

Since:

1.11

createInstance

protected abstract Object createInstance(InstanceCookie[] cookies)
                                  throws IOException,
                                         ClassNotFoundException

Notifies subclasses that the set of cookies for this folder has changed. A new object representing the folder should be created (or the old one updated). Called both upon initialization of the class, and change of its cookies.

It may be poor style for this method to have side-effects. A common way to use FolderInstance is to have this method set some global state which is then used as the resulting instance. Better is to treat the FolderInstance as pure SPI and assign it to a variable of type InstanceCookie. Then use the FolderInstance.instanceCreate() method to get the final result. However in some cases there is a singleton live object which must be updated in-place, and it only makes sense to do so here (in which case the InstanceCookie methods are unused).

Parameters:

cookies - updated array of instance cookies for the folder

Returns:

object to represent these cookies

Throws:

IOException - an I/O error occured

ClassNotFoundException - a class has not been found

instanceForCookie

protected Object instanceForCookie(DataObject obj,
                                   InstanceCookie cookie)
                            throws IOException,
                                   ClassNotFoundException

Method that is called when a the folder instance really wants to create an object from provided cookie. It allows subclasses to overwrite the default behaviour (which is to call InstanceCookie.instanceCreate()).

Parameters:

obj - the data object that is the source of the cookie

cookie - the instance cookie to read the instance from

Throws:

IOException - when there I/O error

ClassNotFoundException - if the class cannot be found

recreate

public void recreate()

Starts recreation of the instance in special thread.

postCreationTask

protected Task postCreationTask(Runnable run)

Invokes the creation of objects in a "safe" thread. This method is for expert subclasses that want to control the thread that the instance is created in.

The default implementation invokes the creation logic in the request processor in non-blocking mode (no other tasks will block on this).

Parameters:

run - runnable to run

Returns:

task to control the execution of the runnable or null if the runnable is run immediatelly

Since:

1.5

toString

public String toString()

Overrides:

toString in class Task