uk.ac.starlink.ttools.plot2.task

Class ParameterFinder<P extends Parameter<?>>

java.lang.Object

uk.ac.starlink.ttools.plot2.task.ParameterFinder<P>

public abstract class ParameterFinder<P extends Parameter<?>>
extends Object

Used for obtaining a parameter qualified by an optional suffix.

In some cases, it is desirable to allow parameters which are logically associated with a layer suffix to be specified without the suffix, for instance if you have three layers using the same table x, it's nice to write "in=x" as a shorthand for "in1=x in2=x in3=x". But if in2=x is present in the environment, that will be used in preference.

Since:

2 Sep 2014

Author:

Mark Taylor

Constructor Summary

Constructors

Constructor and Description
ParameterFinder()

Method Summary

Modifier and Type	Method and Description
abstract P	createParameter(String suffix) Concrete subclasses must implement this method to create a parameter of the right type with an arbitrary suffix.
P	findParameter(Environment env, String fullSuffix) Returns an existing parameter to use for obtaining a value associated with the given layer suffix from the given environment.
P	findParameterByName(String target, String fullSuffix) Attempts to locate a parameter known by this finder with the given name.
P	getParameter(Environment env, String fullSuffix) Calls findParameter(uk.ac.starlink.task.Environment, java.lang.String), but if the result is null, a parameter with the full suffix is returned.

Methods inherited from class java.lang.Object

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

Constructor Detail

ParameterFinder

public ParameterFinder()

Method Detail

createParameter

public abstract P createParameter(String suffix)

Concrete subclasses must implement this method to create a parameter of the right type with an arbitrary suffix.

Parameters:

suffix - arbitrary suffix

Returns:

parameter of with the given suffix

getParameter

public P getParameter(Environment env,
                      String fullSuffix)

Calls findParameter(uk.ac.starlink.task.Environment, java.lang.String), but if the result is null, a parameter with the full suffix is returned. In that case, the environment doesn't already have a value for the parameter, but it may take steps to obtain one (like asking the user).

Parameters:

env - execution environment, possibly populated with values

fullSuffix - suffix associated with the layer for which the value is required

Returns:

parameter for obtaining a value associated with the layer suffix, not null

findParameter

public P findParameter(Environment env,
                       String fullSuffix)

Returns an existing parameter to use for obtaining a value associated with the given layer suffix from the given environment. If the environment contains a value for the parameter with the given suffix, or of any shortened form of that suffix (including the empty string), that parameter is returned. Otherwise, null is returned.

Parameters:

env - execution environment, possibly populated with values

fullSuffix - suffix associated with the layer for which the value is required

Returns:

parameter for obtaining a value associated with the layer suffix, or null

findParameterByName

public P findParameterByName(String target,
                             String fullSuffix)

Attempts to locate a parameter known by this finder with the given name. If it can't be found, return null.

Parameters:

target - required parameter name (not case-sensitive)

fullSuffix - suffix associated with the layer for which the value is required

Returns:

parameter with name target, or null