uk.org.ogsadai.activity.sql
Class SQLQueryStatementActivity

java.lang.Object
  |
  +--uk.org.ogsadai.activity.Activity
        |
        +--uk.org.ogsadai.activity.sql.AbstractSQLActivity
              |
              +--uk.org.ogsadai.activity.sql.AbstractParameterisedSQLActivity
                    |
                    +--uk.org.ogsadai.activity.sql.SQLQueryStatementActivity

Direct Known Subclasses:

CSVQueryStatementActivity

public class SQLQueryStatementActivity

extends AbstractParameterisedSQLActivity

Executes one or a sequence of SQL query statements across a JDBC connection. The activity outputs java.sql.ResultSets.

The SQLQueryStatementActivity is constructed from an Element corresponding to a statement for execution on a database.

The credentials of the user should be available to obtain a connection from the JDBCConnectionProvider.

The activity is then processed a block at a time. On the request for the first block the activity will obtain a connection from the JDBCConnectionProvider. Subsequent calls execute the statement on the database and put the resulting ResultSet object into the output stream.

When there are no more results, the connection is returned to the JDBCConnectionProvider.

Note: Database needs to support java.sql.Connection.setReadOnly otherwise update could slip through, be committed and only then flag an error Extend this class if the database driver does not support all of the methods and flags used here.

A prepared statement will automatically be used if sqlParameters are specified. Parameter valuescan be pulled from an output stream of another activity or may be provided by value in the request.

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

Author:

The OGSA-DAI team.

Field Summary

private static java.lang.String	COPYRIGHT_NOTICE Copyright statement
private static DAILogger	LOG Logger object for logging in this class
private java.sql.Connection	mConnection JDBC database connection handler

Fields inherited from class uk.org.ogsadai.activity.sql.AbstractParameterisedSQLActivity

mParameters

Fields inherited from class uk.org.ogsadai.activity.sql.AbstractSQLActivity

CREATE_DATABASE, DROP_DATABASE, EXPRESSION, mCredentials, mDataResource, mExpression, mInputStreamNames, mOutput, mStatement, RESULT_STREAM, SQL_OUT_PARAMETERS, SQL_PARAMETERS, STORED_PROCEDURE, WEB_ROW_SET_STREAM

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

mContext, mExternalInputs, mExternalOutputs, mInternalInputs, mInternalOutputs

Constructor Summary

SQLQueryStatementActivity(org.w3c.dom.Element element)
Constructs an activity using the specified element.

Method Summary

protected void	cleanUp() This method can be overridden by any Activity implementations that need to free up resources in the event of an error or intermediate termination of the activity processing.
protected void	processBlock() Performs an iteration of the processing of an activity.
protected void	processFirst() This method is called during the first iteration of processing an activity.

Methods inherited from class uk.org.ogsadai.activity.sql.AbstractParameterisedSQLActivity

initialise, initialiseInputStreamNames, parseSQLParameters

Methods inherited from class uk.org.ogsadai.activity.sql.AbstractSQLActivity

createOutputPipe, parseExpression, parseResultStream

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

connectsTo, 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 DAILogger LOG

Logger object for logging in this class

mConnection

private java.sql.Connection mConnection

JDBC database connection handler

Constructor Detail

SQLQueryStatementActivity

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

Constructs an activity using the specified element.

Parameters:

element - Element to configure the activity with - from a perform document.

Throws:

ActivityCreationException - If there is a problem constructing the activity.

ActivitySpecificationException - If there is a problem constructing the activity due to an invalid setting in element.

See Also:

uk.org.ogsadai.activity

Method Detail

processFirst

protected void processFirst()

Description copied from class: Activity

This method is called during the first iteration of processing an activity. It can be overridden by subclasses to define some processing that should be done only once during the first iteration of the activity processing, for example evaluating a database query.

Overrides:

processFirst in class Activity

processBlock

protected 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

cleanUp

protected void cleanUp()

Description copied from class: Activity

This method can be overridden by any Activity implementations that need to free up resources in the event of an error or intermediate termination of the activity processing.

Overrides:

cleanUp in class Activity