uk.ac.starlink.ttools.task

Class ConsumerTask

java.lang.Object

uk.ac.starlink.ttools.task.ConsumerTask

All Implemented Interfaces:

Task

Direct Known Subclasses:

MapperTask, RegQuery, SingleMapperTask, TableCone, TableLoop, TapResume

public abstract class ConsumerTask
extends Object
implements Task

Abstract task which takes an input table and disposes of it. Concrete subclasses must supply the table.

Since:

29 Aug 2005

Author:

Mark Taylor

Constructor Summary

Constructors

Constructor and Description
ConsumerTask(String purpose, ProcessingMode outMode, boolean useOutFilter) Constructor.

Method Summary

Modifier and Type	Method and Description
Executable	createExecutable(Environment env) Creates an executable object which will do the work of this task in the given Environment.
abstract TableProducer	createProducer(Environment env) Returns an object which can produce the effective output table which will be consumed by this task.
static TableProducer	createProducer(Environment env, FilterParameter filterParam, InputTableParameter inParam) Constructs a table producer given an input parameter and an input filter parameter.
static String	getIdentity(StarTable table) Returns an identification string for a table that has been produced by the TableProducer from this class's createProducer(uk.ac.starlink.task.Environment) method.
ProcessingMode	getOutputMode() Returns this task's output mode.
protected List<Parameter<?>>	getParameterList() Returns the parameter list for this task; it may be modified.
Parameter<?>[]	getParameters() Returns the list of parameters which may be used by this task.
String	getPurpose() Returns a short (one-line) description of the purpose of this task.

Methods inherited from class java.lang.Object

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

Constructor Detail

ConsumerTask

public ConsumerTask(String purpose,
                    ProcessingMode outMode,
                    boolean useOutFilter)

Constructor.

Parameters:

purpose - one-line description of the task

outMode - processing mode which determines the destination of the processed table

useOutFilter - allow specification of filters for output table

Method Detail

getPurpose

public String getPurpose()

Description copied from interface: Task

Returns a short (one-line) description of the purpose of this task.

Specified by:

getPurpose in interface Task

Returns:

plain text description of this task's purpose

getParameters

public Parameter<?>[] getParameters()

Description copied from interface: Task

Returns the list of parameters which may be used by this task.

Specified by:

getParameters in interface Task

Returns:

an array of the Parameter objects this task may request values for during its invocation

getParameterList

protected List<Parameter<?>> getParameterList()

Returns the parameter list for this task; it may be modified.

Returns:

parameter list

createProducer

public abstract TableProducer createProducer(Environment env)
                                      throws TaskException

Returns an object which can produce the effective output table which will be consumed by this task. The table produced by the resulting producer can be fed to the getIdentity(uk.ac.starlink.table.StarTable) method.

Parameters:

env - execution environment

Returns:

table producer

Throws:

TaskException

createExecutable

public Executable createExecutable(Environment env)
                            throws TaskException

Description copied from interface: Task

Creates an executable object which will do the work of this task in the given Environment. This method should do all of the parameter processing and prepare an object which just executes. The idea is that any communication with the user related to the supplied parameter values can be done before the task starts to execute in earnest. Consequently, the returned Executable object ought not to make any reference to env, though this is not absolutely prohibited.

Specified by:

createExecutable in interface Task

Parameters:

env - the environment in which the task will operate

Throws:

TaskException - if no executable can be created; this should usually be a UsageException or some subclass

getOutputMode

public ProcessingMode getOutputMode()

Returns this task's output mode.

Returns:

output mode

createProducer

public static TableProducer createProducer(Environment env,
                                           FilterParameter filterParam,
                                           InputTableParameter inParam)
                                    throws TaskException

Constructs a table producer given an input parameter and an input filter parameter. Tables which are generated by equal input parameters will evaluate as equal in the sense of Object.equals().

Parameters:

env - execution environment

filterParam - parameter giving filter steps (or null)

inParam - parameter giving input table

Returns:

table producer, or null if the table input parameter has a (permitted) blank value

Throws:

TaskException

getIdentity

public static String getIdentity(StarTable table)

Returns an identification string for a table that has been produced by the TableProducer from this class's createProducer(uk.ac.starlink.task.Environment) method. This string amalgamates the table location and any filters applied to produce it, so it should be usable elsewhere, including in unrelated JVMs, to identify a table.

Parameters:

table - input table produced by this task

Returns:

unique table identifier