com.yahoo.documentapi

Class VisitorDataHandler

java.lang.Object

com.yahoo.documentapi.VisitorDataHandler

Direct Known Subclasses:

DumpVisitorDataHandler, VisitorDataQueue

public abstract class VisitorDataHandler
extends Object

A data handler is a class that handles responses from a visitor. Different clients might want different interfaces. Some might want a callback interface, some might want a polling interface. Some want good control of acking, while others just want something simple.

Use a data handler that fits your needs to be able to use visiting easily.

Author:

Håkon Humberset

Field Summary

Fields

Modifier and Type	Field and Description
protected VisitorControlSession	session

Constructor Summary

Constructors

Constructor and Description
VisitorDataHandler() Creates a new visitor data handler.

Method Summary

Modifier and Type	Method and Description
void	ack(AckToken token) Function used to ack data.
VisitorResponse	getNext() Returns the next response of this session.
VisitorResponse	getNext(int timeoutMilliseconds) Returns the next response of this session.
void	onDone() Called when visiting is done, to notify clients waiting on getNext().
abstract void	onMessage(com.yahoo.messagebus.Message m, AckToken token) Called when a data message is received.
void	reset() Called before the visitor starts.
void	setSession(VisitorControlSession session) Sets which session this visitor data handler belongs to.

Methods inherited from class java.lang.Object

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

Field Detail

session

protected VisitorControlSession session

Constructor Detail

VisitorDataHandler

public VisitorDataHandler()

Creates a new visitor data handler.

Method Detail

reset

public void reset()

Called before the visitor starts. Override this method if you need to reset local data. Remember to call the superclass' method as well.

setSession

public void setSession(VisitorControlSession session)

Sets which session this visitor data handler belongs to. This is done by the session itself and should not be called manually. The session is needed for ack to work.

Parameters:

session - the session currently using this data handler

getNext

public VisitorResponse getNext()

Returns the next response of this session. This method returns immediately.

Returns:

the next response, or null if no response is ready at this time

Throws:

UnsupportedOperationException - if data handler does not support the operation

getNext

public VisitorResponse getNext(int timeoutMilliseconds)
                        throws InterruptedException

Returns the next response of this session. This will block until a response is ready or the given timeout is reached.

Parameters:

timeoutMilliseconds - the max time to wait for a response. If the number is 0, this will block without any timeout limit

Returns:

the next response, or null if no response becomes ready before the timeout expires

Throws:

InterruptedException - if this thread is interrupted while waiting

UnsupportedOperationException - if data handler does not support the operation

onDone

public void onDone()

Called when visiting is done, to notify clients waiting on getNext().

onMessage

public abstract void onMessage(com.yahoo.messagebus.Message m,
                               AckToken token)

Called when a data message is received. IMPORTANT: May be called concurrently from multiple threads. Any internal state mutations MUST be done in a thread-safe manner.

Parameters:

m - The message received

token - A token to reply with when finished processing the message.

ack

public void ack(AckToken token)

Function used to ack data. You need to ack data periodically, as storage will halt visiting when it has too much client requests pending.

Parameters:

token - The token to ack. Gotten from an earlier callback.