uk.ac.starlink.array

Class NDArrayFactory

java.lang.Object

uk.ac.starlink.array.NDArrayFactory

public class NDArrayFactory
extends Object

Manufactures NDArray objects from URLs. Methods are available to construct a readable NDArray from a URL pointing to an existing array resource, or to construct a new NDArray with a location given by a URL.

This factory delegates the actual NDArray creation to external ArrayBuilder objects; the URL is passed to each one in turn until one can make an NDArray object from it, which object is returned to the caller.

By default, if the corresponding classes are present, the following ArrayBuilders are installed:

• HDSArrayBuilder
• FitsArrayBuilder

Consult the documentation of these classes to find out about the format of URLs understood by each.

Author:

Mark Taylor (Starlink)

Constructor Summary

Constructors

Constructor and Description
NDArrayFactory() Constructs an NDArrayFactory with a default list of builders.

Method Summary

Modifier and Type	Method and Description
List	getBuilders() Gets the list of builders which actually do the URL->NDArray construction.
NDArray	makeNDArray(String location, AccessMode mode) Constructs a readable NDArray from a location representing an existing resource.
NDArray	makeNDArray(URL url, AccessMode mode) Constructs a readable NDArray from a URL representing an exisiting resource.
NDArray	makeNewNDArray(String location, NDArray template) Constructs a new NDArray to which data can be written given a location and another template NDArray.
NDArray	makeNewNDArray(String location, NDShape shape, Type type, BadHandler bh) Constructs a new NDArray to which data can be written given a location and the array characteristics.
NDArray	makeNewNDArray(URL url, NDArray template) Constructs a new NDArray to which data can be written given a URL and another template NDArray.
NDArray	makeNewNDArray(URL url, NDShape shape, Type type, BadHandler bh) Constructs a new NDArray to which data can be written given a URL and the array characteristics.
void	setBuilders(ArrayBuilder[] builders) Sets the list of builders which actually do the URL->NDArray construction Builders earlier in the list are given a chance to handle a URL before ones later in the list.

Methods inherited from class java.lang.Object

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

Constructor Detail

NDArrayFactory

public NDArrayFactory()

Constructs an NDArrayFactory with a default list of builders.

Method Detail

getBuilders

public List getBuilders()

Gets the list of builders which actually do the URL->NDArray construction. Builders earlier in the list are given a chance to handle a URL before ones later in the list. This list may be modified to change the behaviour of the NDArrayFactory.

Returns:

a mutable List of ArrayBuilder objects used for turning URLs into NDArrays

setBuilders

public void setBuilders(ArrayBuilder[] builders)

Sets the list of builders which actually do the URL->NDArray construction Builders earlier in the list are given a chance to handle a URL before ones later in the list.

Parameters:

builders - an array of ArrayBuilder objects used for turning URLs into NDArrays

makeNDArray

public NDArray makeNDArray(URL url,
                           AccessMode mode)
                    throws IOException

Constructs a readable NDArray from a URL representing an exisiting resource. A null result will be returned if none of the available builders understands the URL; an IOException will result if one of the builders is willing to handle the URL but fails to find an array resource at it.

Parameters:

url - a URL pointing to a resource holding array data

mode - the mode with which it should be accessed

Returns:

a readable NDArray object view of the data at url, or null if one could not be found

Throws:

IOException - if there is any I/O error

makeNewNDArray

public NDArray makeNewNDArray(URL url,
                              NDShape shape,
                              Type type,
                              BadHandler bh)
                       throws IOException

Constructs a new NDArray to which data can be written given a URL and the array characteristics. A null result will be returned if none of the available builders understands the URL; an IOException will result if one of the builders is willing to handle the URL but fails to make an array resource at it.

The bh parameter indicates a requested bad value handling scheme, but does not guarantee that it will be used, since not all storage formats are capable of storing bad values in arbitrary ways. According to the resource type, bad value handling will be provided on a best-efforts basis. If bh is null, the implementation will choose a bad value handling policy of its own.

Parameters:

url - a URL pointing to a writable resource. This may be a suitable file:-protocol URL or one with some other protocol which can provide an output-capable connection

shape - the shape of the new array

type - a Type object indicating the type of data in the array

bh - the requested bad value handling policy - see above.

Returns:

a new writable NDArray object with the given URL, or null if none could be constructed because none of the handlers recognised the URL

Throws:

IOException - if an I/O error occurs

IllegalArgumentException - if the type of bh does not match type

makeNewNDArray

public NDArray makeNewNDArray(URL url,
                              NDArray template)
                       throws IOException

Constructs a new NDArray to which data can be written given a URL and another template NDArray. This convenience method simply calls makeNewNDArray(URL,NDShape,Type,BadHandler) with the shape, type and bh parameters copied from the template NDArray.

Parameters:

url - a URL pointing to a writable resource. This may be a suitable file:-protocol URL or one with some other protocol which can provide an output-capable connection

template - an NDArray whose characteristics are to be copied when the new one is created

Returns:

a new writable NDArray object with the given URL

Throws:

IOException - if an I/O error occurs

makeNDArray

public NDArray makeNDArray(String location,
                           AccessMode mode)
                    throws IOException

Constructs a readable NDArray from a location representing an existing resource. This convenience method just turns the location into a URL and calls makeNDArray(URL,AccessMode).

Parameters:

location - the location of the resource. If it cannot be parsed as a URL, it will be treated as a filename

mode - the mode with which it should be accessed

Returns:

a readable NDArray object view of the data at location, or null if one could not be found

Throws:

IOException - if there is any I/O error

makeNewNDArray

public NDArray makeNewNDArray(String location,
                              NDShape shape,
                              Type type,
                              BadHandler bh)
                       throws IOException

Constructs a new NDArray to which data can be written given a location and the array characteristics. This convenience method just turns the location into a URL and calls makeNewNDArray(URL,NDShape,Type,BadHandler)

Parameters:

location - the location of the resource. If it cannot be parsed as a URL, it will be treated as a filename

shape - the shape of the new array

type - a Type object indicating the type of data in the array

bh - requested bad value handling policy

Returns:

a new writable NDArray object at the given location, or null if none could be constructed because none of the handlers recognised the URL

Throws:

IOException - if an I/O error occurs

makeNewNDArray

public NDArray makeNewNDArray(String location,
                              NDArray template)
                       throws IOException

Constructs a new NDArray to which data can be written given a location and another template NDArray. This convenience method just turns the location into a URL and calls makeNewNDArray(URL,NDArray).

Parameters:

location - the location of the resource. If it cannot be parsed as a URL, it will be treated as a filename

template - an NDArray whose characteristics are to be copied when the new one is created

Returns:

a new writable NDArray object at the given location

Throws:

IOException - if an I/O error occurs