jade.core.behaviours
Class Behaviour

java.lang.Object
  jade.core.behaviours.Behaviour

All Implemented Interfaces:

java.io.Serializable

Direct Known Subclasses:

CompositeBehaviour, LoaderBehaviour, ReceiverBehaviour, SimpleBehaviour, ThreadedBehaviourFactory.ThreadedBehaviourWrapper, WrapperBehaviour

public abstract class Behaviour
extends java.lang.Object
implements Serializable

Abstract base class for JADE behaviours. Extending this class directly should only be needed for particular behaviours with special synchronization needs; this is because event based notification used for blocking and restarting behaviours is directly accessible at this level.

Version:

$Date: 2011-04-19 17:09:16 +0200(mar, 19 apr 2011) $ $Revision: 6403 $

Author:

Giovanni Rimassa - Universita' di Parma

See Also:

Serialized Form

Nested Class Summary

protected class

Behaviour.RunnableChangedEvent Event class for notifying blocked and restarted behaviours.

Field Summary

protected Agent	myAgent The agent this behaviour belongs to.
protected Behaviour.RunnableChangedEvent	myEvent This event object will be re-used for every state change notification.
protected static int	NOTIFY_DOWN A constant for parent-to-child notifications.
protected static int	NOTIFY_UP A constant for child-to-parent notifications.
protected CompositeBehaviour	parent
static java.lang.String	STATE_BLOCKED A constant identifying the blocked state.
static java.lang.String	STATE_READY A constant identifying the runnable state.
static java.lang.String	STATE_RUNNING A constant identifying the running state.

Constructor Summary

Behaviour()
Default constructor.

Behaviour(Agent a)
Constructor with owner agent.

Method Summary

abstract void	action() Runs the behaviour.
void	actionWrapper() This method is called internally by the JADE framework and should not be called by the user.
void	block() Blocks this behaviour.
void	block(long millis) Blocks this behaviour for a specified amount of time.
abstract boolean	done() Check if this behaviour is done.
java.lang.String	getBehaviourName() Retrieve the name of this behaviour object.
DataStore	getDataStore() Return the private data store of this Behaviour.
java.lang.String	getExecutionState()
protected CompositeBehaviour	getParent() Retrieve the enclosing CompositeBehaviour (if present).
long	getRestartCounter() This method is used internally by the framework.
protected void	handle(Behaviour.RunnableChangedEvent rce) Handler for block/restart events.
protected void	handleBlockEvent() This method is used internally by the framework.
void	handleRestartEvent() This method is used internally by the framework.
boolean	isRunnable() Returns whether this Behaviour object is blocked or not.
int	onEnd() This method is just an empty placeholder for subclasses.
void	onStart() This method is just an empty placeholders for subclasses.
void	reset() Restores behaviour initial state.
void	restart() Restarts a blocked behaviour.
Behaviour	root() Returns the root for this Behaviour object.
void	setAgent(Agent a) Associates this behaviour with the agent it belongs to.
void	setBehaviourName(java.lang.String name) Give a name to this behaviour object.
void	setDataStore(DataStore ds) Set the private data store of this Behaviour
void	setExecutionState(java.lang.String s)

Methods inherited from class java.lang.Object

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

Field Detail

NOTIFY_UP

protected static final int NOTIFY_UP

A constant for child-to-parent notifications.

See Also:

Constant Field Values

NOTIFY_DOWN

protected static final int NOTIFY_DOWN

A constant for parent-to-child notifications.

See Also:

Constant Field Values

STATE_READY

public static final java.lang.String STATE_READY

A constant identifying the runnable state.

See Also:

Constant Field Values

STATE_BLOCKED

public static final java.lang.String STATE_BLOCKED

A constant identifying the blocked state.

See Also:

Constant Field Values

STATE_RUNNING

public static final java.lang.String STATE_RUNNING

A constant identifying the running state.

See Also:

Constant Field Values

myAgent

protected Agent myAgent

The agent this behaviour belongs to. This is an instance variable that holds a reference to the Agent object and allows the usage of its methods within the body of the behaviour. As the class Behaviour is the superclass of all the other behaviour classes, this variable is always available. Of course, remind to use the appropriate constructor, i.e. the one that accepts an agent object as argument; otherwise, this variable is set to null.

myEvent

protected Behaviour.RunnableChangedEvent myEvent

This event object will be re-used for every state change notification.

parent

protected CompositeBehaviour parent

Constructor Detail

Behaviour

public Behaviour()

Default constructor. It does not set the agent owning this behaviour object.

Behaviour

public Behaviour(Agent a)

Constructor with owner agent.

Parameters:

a - The agent owning this behaviour.

Method Detail

getParent

protected CompositeBehaviour getParent()

Retrieve the enclosing CompositeBehaviour (if present). In order to access the parent behaviour it is strongly suggested to use this method rather than the parent member variable directly. In case of threaded or wrapped behaviour in facts the latter may have unexpected values.

Returns:

The enclosing CompositeBehaviour (if present).

See Also:

CompositeBehaviour

setBehaviourName

public final void setBehaviourName(java.lang.String name)

Give a name to this behaviour object.

Parameters:

name - The name to give to this behaviour.

getBehaviourName

public final java.lang.String getBehaviourName()

Retrieve the name of this behaviour object. If no explicit name was set, a default one is given, based on the behaviour class name.

Returns:

The name of this behaviour.

action

public abstract void action()

Runs the behaviour. This abstract method must be implemented by Behavioursubclasses to perform ordinary behaviour duty. An agent schedules its behaviours calling their action() method; since all the behaviours belonging to the same agent are scheduled cooperatively, this method must not enter in an endless loop and should return as soon as possible to preserve agent responsiveness. To split a long and slow task into smaller section, recursive behaviour aggregation may be used.

See Also:

CompositeBehaviour

done

public abstract boolean done()

Check if this behaviour is done. The agent scheduler calls this method to see whether a Behaviour still need to be run or it has completed its task. Concrete behaviours must implement this method to return their completion state. Finished behaviours are removed from the scheduling queue, while others are kept within to be run again when their turn comes again.

Returns:

true if the behaviour has completely executed.

onEnd

public int onEnd()

This method is just an empty placeholder for subclasses. It is invoked just once after this behaviour has ended. Therefore, it acts as an epilog for the task represented by this Behaviour.
Note that onEnd is called after the behaviour has been removed from the pool of behaviours to be executed by an agent. Therefore calling reset() is not sufficient to cyclically repeat the task represented by this Behaviour. In order to achieve that, this Behaviour must be added again to the agent (using myAgent.addBehaviour(this)). The same applies to in the case of a Behaviour that is a child of a ParallelBehaviour.

Returns:

an integer code representing the termination value of the behaviour.

onStart

public void onStart()

This method is just an empty placeholders for subclasses. It is executed just once before starting behaviour execution. Therefore, it acts as a prolog to the task represented by this Behaviour.

actionWrapper

public final void actionWrapper()

This method is called internally by the JADE framework and should not be called by the user.

setExecutionState

public final void setExecutionState(java.lang.String s)

getExecutionState

public final java.lang.String getExecutionState()

reset

public void reset()

Restores behaviour initial state. This method must be implemented by concrete subclasses in such a way that calling reset() on a behaviour object is equivalent to destroying it and recreating it back. The main purpose for this method is to realize multistep cyclic behaviours without needing expensive constructions an deletion of objects at each loop iteration. Remind to call super.reset() from the sub-classes.

handle

protected void handle(Behaviour.RunnableChangedEvent rce)

Handler for block/restart events. This method handles notification by copying its runnable state and then by simply forwarding the event when it is travelling upwards and by doing nothing when it is travelling downwards, since an ordinary behaviour has no children.

Parameters:

rce - The event to handle

root

public Behaviour root()

Returns the root for this Behaviour object. That is, the top-level behaviour this one is a part of. Agents apply scheduling only to top-level behaviour objects, so they just call restart() on root behaviours.

Returns:

The top-level behaviour this behaviour is a part of. If this one is a top level behaviour itself, then simply this is returned.

See Also:

restart()

isRunnable

public boolean isRunnable()

Returns whether this Behaviour object is blocked or not.

Returns:

true when this behaviour is not blocked, false when it is.

getRestartCounter

public final long getRestartCounter()

This method is used internally by the framework. Developer should not call or redefine it.

block

public void block()

Blocks this behaviour. It should be noticed that this method is NOT a blocking call: when it is invoked, the internal behaviour state is set to Blocked so that, as soon as the action() method returns, the behaviour is put into a blocked behaviours queue so that it will not be scheduled anymore.
The behaviour is moved back in the pool of active behaviours when either a message is received or the behaviour is explicitly restarted by means of its restart() method.
If this behaviour is a child of a CompositeBehaviour a suitable event is fired to notify its parent behaviour up to the behaviour composition hierarchy root.

See Also:

restart()

handleBlockEvent

protected void handleBlockEvent()

This method is used internally by the framework. Developer should not call or redefine it.

block

public void block(long millis)

Blocks this behaviour for a specified amount of time. The behaviour will be restarted when among the three following events happens.

• A time of millis milliseconds has passed since the call to block().
• An ACL message is received by the agent this behaviour belongs to.
• Method restart() is called explicitly on this behaviour object.

Parameters:

millis - The amount of time to block, in milliseconds. Notice: a value of 0 for millis is equivalent to a call to block() without arguments.

See Also:

block()

restart

public void restart()

Restarts a blocked behaviour. This method fires a suitable event to notify this behaviour's parent. When the agent scheduler inserts a blocked event back into the agent ready queue, it restarts it automatically. When this method is called, any timer associated with this behaviour object is cleared.

See Also:

block()

handleRestartEvent

public void handleRestartEvent()

This method is used internally by the framework. Developer should not call or redefine it.

setAgent

public void setAgent(Agent a)

Associates this behaviour with the agent it belongs to. There is no need to call this method explicitly, since the addBehaviour() call takes care of the association transparently.

Parameters:

a - The agent this behaviour belongs to.

See Also:

Agent.addBehaviour(Behaviour b)

getDataStore

public DataStore getDataStore()

Return the private data store of this Behaviour. If it was null, a new DataStore is created and returned.

Returns:

The private data store of this Behaviour

setDataStore

public void setDataStore(DataStore ds)

Set the private data store of this Behaviour

Parameters:

ds - the DataStore that this Behaviour will use as its private data store