distrit.server
Class FineGrainedInteractiveTasks

java.lang.Object
  |
  +--distrit.server.FineGrainedInteractiveTasks

All Implemented Interfaces:

InteractiveTask, java.io.Serializable, Task

public class FineGrainedInteractiveTasks

extends java.lang.Object

implements InteractiveTask

Provides an abstraction to run many interactive tasks concurrently so that if one stops before others it can be replaced by a new task. It also enables tasks to be replaced at any time by the server.

This is achieved by the server being informed of which tasks are still alive when it calls the get method and by the server sending out the same or new tasks through the set method. If the same task as the current one is sent then it is ignored. WARNING: Task equality is based on the toString() method.

If a task is sent that the client has previously completed there is an option to ignore this task, but the current implementation will run this task anyway since in many cases this is not a useless functionality. To reenable this option see line marked with **!!.

This assumes InteractiveTask implementations will be well behaved and check their currentThread.isInterrupted() method.

See Also:

Serialized Form

Field Summary

static int	CONTROL_INDEX Index within the Vector sent to the set method of this task for which task control information is sent.
static int	DATA_INDEX Index within the Vector sent to the set method of this task for which task data information is sent.

Constructor Summary

FineGrainedInteractiveTasks()
Creates new FineGrainedInteractiveTasks

FineGrainedInteractiveTasks(java.util.Vector tasks)
Creates new FineGrainedInteractiveTasks

Method Summary

java.lang.Object	get(java.lang.Object params) Used to get output from the tasks plus a Boolean saying if they're alive.
java.lang.Object	run(java.lang.Object params) Starts all tasks in their own thread
void	set(java.lang.Object paramsAndWhat) Used to send input to each of the tasks or to replace these tasks.
java.lang.String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

CONTROL_INDEX

public static final int CONTROL_INDEX

Index within the Vector sent to the set method of this task for which task control information is sent. This information will define if the current task should be continued or a new one started.

DATA_INDEX

public static final int DATA_INDEX

Index within the Vector sent to the set method of this task for which task data information is sent. This is data sent to the set method of each subtask

Constructor Detail

FineGrainedInteractiveTasks

public FineGrainedInteractiveTasks()

Creates new FineGrainedInteractiveTasks

FineGrainedInteractiveTasks

public FineGrainedInteractiveTasks(java.util.Vector tasks)

Creates new FineGrainedInteractiveTasks

Parameters:

tasks -

Method Detail

get

public java.lang.Object get(java.lang.Object params)

Used to get output from the tasks plus a Boolean saying if they're alive.

Specified by:

get in interface InteractiveTask

Parameters:

params - can be null if this task doesn't need to know WHAT it has to output

Returns:

Vector of (Object, Boolean) pairs (which are Vectors of size 2)

set

public void set(java.lang.Object paramsAndWhat)

Used to send input to each of the tasks or to replace these tasks. To replace a task a new InteractiveTask must be sent in the pairs, this method will try and work out if the task has been done before and if so ignore it (currently not functional because repeating tasks is useful). Task equality is based on their toString() method's output.

Specified by:

set in interface InteractiveTask

Parameters:

paramsAndWhat - must be a vector of (Object, InteractiveTask) pairs (vector of 2) with what must be sent to each task and a new task if necesary.

run

public java.lang.Object run(java.lang.Object params)
                     throws java.lang.InterruptedException

Starts all tasks in their own thread

Specified by:

run in interface Task

Parameters:

params - Vector containing initial parameters to send to each run method of encapsulated tasks

Returns:

Vector containing values returned by all tasks that were run. If multiple tasks were run in a single index then the last one replaces previous ones. This method only returns when all tasks have completed execution of their own run method.

Throws:

java.lang.InterruptedException - If any task is interruped.

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object