uk.org.ogsadai.activity.sql
Class RemoveDuplicatesWebRowSetActivity

java.lang.Object
  |
  +--uk.org.ogsadai.activity.Activity
        |
        +--uk.org.ogsadai.activity.sql.RemoveDuplicatesWebRowSetActivity

public class RemoveDuplicatesWebRowSetActivity

extends Activity

This activity is used to remove duplicate records (rows) in a query result from multiple relational data service resources (exposed by data services).

It has one input and one output. The input must be a WebRowSet. Typically the activity providing this will be an SQLBag activity so that a union operation is performed. The output is the transformed WebRowSet document.

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

Author:

The OGSA-DAI Project Team

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 this activity

mInput

private BlockReader mInput

Activity input.

mOutput

private BlockWriter mOutput

Activity output - WebRowSet

myBuf

private java.lang.StringBuffer myBuf

Store all from the input before processing. This may means memory limitation for large WebRowSets.

RemoveDuplicatesWebRowSetActivity

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

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 Activity

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 Activity

removeDup

private java.lang.String removeDup(java.lang.String inputRowSet)
                            throws XMLDocumentException,
                                   XMLParseException

Remove duplicate rows of a WebRowSet.

Parameters:

inputRowSet - WebRowSet in a string.

Returns:

a string WebRowSet which contains unique rows.

Throws:

XMLParseException - If the string does not contain valid XML.

XMLDocumentException - If some internal problem occurs when parsing.