uk.org.ogsadai.activity.delivery
Class AbstractDeliverFromDTActivity

java.lang.Object
  |
  +--uk.org.ogsadai.activity.Activity
        |
        +--uk.org.ogsadai.activity.delivery.AbstractDTDeliveryActivity
              |
              +--uk.org.ogsadai.activity.delivery.AbstractDeliverFromDTActivity

Direct Known Subclasses:

DeliverFromGDTActivity

public abstract class AbstractDeliverFromDTActivity

extends AbstractDTDeliveryActivity

This activity gets data from a stream exposed by an active session of a data service resource exposed by a data service. The data transport getFully/NBlocks/Block) operations on the service are used to pull the data to this activity.

For information on this activity see the OGSA-DAI user doc: OGSA-DAI/doc/interaction/activities/delivery/deliverFromGDT.html

Author:

The OGSA-DAI Project Team

Field Summary

private static java.lang.String	COPYRIGHT_NOTICE Copyright statement
private static DAILogger	LOG Logger object for logging in this class.
protected int	mNumBlocks Number of blocks to transfer if transfer mode is "block"
private BlockWriter	mOutput Activity output stream.

Fields inherited from class uk.org.ogsadai.activity.delivery.AbstractDTDeliveryActivity

mBlockMode, mDeliveryNode, mLocalStream, mResourceID, mServiceType, mServiceURL, mStreamID

Fields inherited from class uk.org.ogsadai.activity.Activity

mContext, mExternalInputs, mExternalOutputs, mInternalInputs, mInternalOutputs

Constructor Summary

AbstractDeliverFromDTActivity(org.w3c.dom.Element element)

Method Summary

protected abstract java.lang.Object	getFully() Retrieve data from the target data service.
protected abstract java.lang.Object	getNBlocks(int numBlocks) Retrieve a number of blocks of data from the target data service.
void	initialise() This method should be overridden by subclasses to perform any initialisation they require before the process method invocations begin.
void	processBlock() Performs an iteration of the processing of an activity.

Methods inherited from class uk.org.ogsadai.activity.delivery.AbstractDTDeliveryActivity

contactTargetService, getDeliverySettings, isServiceUnknown, isServiceWSI, isServiceWSRF, processFirst

Methods inherited from class uk.org.ogsadai.activity.Activity

cleanUp, connectsTo, createOutputPipe, getActivityConfiguration, getActivityName, getCause, getName, getObservableStatus, getProperties, getSession, getStatus, hasActivityConfiguration, hasProperties, process, setActivityName, setCompleted, setError

Methods inherited from class java.lang.Object

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

Field Detail

COPYRIGHT_NOTICE

private static final java.lang.String COPYRIGHT_NOTICE

Copyright statement

See Also:

Constant Field Values

LOG

private static final DAILogger LOG

Logger object for logging in this class.

mOutput

private BlockWriter mOutput

Activity output stream.

mNumBlocks

protected int mNumBlocks

Number of blocks to transfer if transfer mode is "block"

Constructor Detail

AbstractDeliverFromDTActivity

public AbstractDeliverFromDTActivity(org.w3c.dom.Element element)
                              throws ActivityCreationException,
                                     ActivitySpecificationException

Method Detail

initialise

public void initialise()
                throws ActivitySpecificationException,
                       ActivityExecutionException

Description copied from class: Activity

This method should be overridden by subclasses to perform any initialisation they require before the process method invocations begin. This might be used for setting up convenient fields to reference objects contained in the context. It shouldn't be used for opening resources. That should be done in processFirst.

Overrides:

initialise in class AbstractDTDeliveryActivity

Throws:

ActivityExecutionException - If some system problem prevents the activity from initialising.

ActivitySpecificationException - If a problem with settings provided by a client prevents the activity from initialising.

processBlock

public void processBlock()

Description copied from class: Activity

Performs an iteration of the processing of an activity. This may involve reading a block of input data and writing a block of output data, or may involve some other kind of processing. When an activity is processed by the OGSA-DAI engine, this method will be invoked repeatedly until the activity either completes or stops due to an error or termination call. An implementation of this method should invoke the setCompleted method to indicate that processing is complete, or the setError method if an error occurs that will prevent the processing from completing.

Specified by:

processBlock in class AbstractDTDeliveryActivity

getFully

protected abstract java.lang.Object getFully()
                                      throws ActivitySpecificationException,
                                             ActivityExecutionException

Retrieve data from the target data service.

Returns:

retrieved data.

Throws:

ActivitySpecificationException - If an error occurs that is caused by incorrect information in the request e.g. the URL is incorrect or cannot be contacted.

ActivityExecutionException - If some internal problem outwith the client's control occurs.

getNBlocks

protected abstract java.lang.Object getNBlocks(int numBlocks)
                                        throws ActivitySpecificationException,
                                               ActivityExecutionException

Retrieve a number of blocks of data from the target data service.

Parameters:

numBlocks - Number of blocks to retrieve.

Returns:

retrieved data.

Throws:

ActivitySpecificationException - If an error occurs that is caused by incorrect information in the request e.g. the URL is incorrect or cannot be contacted.

ActivityExecutionException - If some internal problem outwith the client's control occurs.