uk.ac.starlink.table

Class StarTableFactory

java.lang.Object

uk.ac.starlink.table.StarTableFactory

public class StarTableFactory
extends java.lang.Object

Manufactures StarTable objects from generic inputs. This factory delegates the actual table creation to external TableBuilder objects, each of which knows how to read a particular table format from an input data stream. Various makeStarTable methods are offered, which construct StarTables from different types of object, such as URL and DataSource. Each of these comes in two types: automatic format detection and named format. Additionally, a list of TableScheme objects is maintained, each of which can produce a table from an opaque specification string of the form :<scheme-name>:<spec>.

In the case of a named format, a specifier must be given for the format in which the table to be read is held. This may be one of the following:

• The format name - this is a short mnemonic string like "fits" which is returned by the TableBuilder's getFormatName method - it is matched case insensitively. This must be one of the builders known to the factory.
• The classname of a suitable TableBuilder (the class must implement TableBuilder and have no-arg constructor). Such a class must be on the classpath, but need not have been specified previously to the factory.
• The empty string or null or AUTO_HANDLER - in this case automatic format detection is used.

In the case of automatic format detection (no format specified), the factory hands the table location to each of the handlers in the default handler list in turn, and if any of them can make a table out of it, it is returned.

In either case, failure to make a table will usually result in a TableFormatException, though if an error in actual I/O is encountered an IOException may be thrown instead.

By default, if the corresponding classes are present, the following TableBuilders are installed in the default handler list (used by default in automatic format detection):

• FitsPlusTableBuilder (format name="fits-plus")
• ColFitsPlusTableBuilder (format name="colfits-plus")
• ColFitsTableBuilder (format name="colfits-basic")
• FitsTableBuilder (format name="fits")
• VOTableBuilder (format name="votable")
• CdfTableBuilder (format name="cdf")
• EcsvTableBuilder (format name="ecsv")
• Pds4TableBuilder (format name="pds4")
• MrtTableBuilder (format name="mrt")
• ParquetTableBuilder (format name="parquet")
• FeatherTableBuilder (format name="feather")

The following additional handlers are installed in the known handler list (not used by default but available by specifying the format name):

• AsciiTableBuilder (format name="ascii")
• CsvTableBuilder (format name="csv")
• TstTableBuilder (format name="tst")
• IpacTableBuilder (format name="ipac")
• GbinTableBuilder (format name="gbin")
• WDCTableBuilder (format name="wdc")

Additionally, any classes named in the startable.readers system property (as a colon-separated list) which implement the TableBuilder interface and have a no-arg constructor will be instantiated and added to the known handler list.

Some makeStarTable methods take a location String rather than an input stream or DataSource; these may either give a URL or filename, or a scheme-based location of the form :<scheme-name>:<scheme-specification>, for instance "jdbc://localhost/db1#SELECT id FROM gsc". There is a theoretical risk of a namespace clash between input-yielding URLs, or even filenames, and scheme-based locations, but if scheme names avoid obvious values like "http" and "C" this is not likely to cause problems in practice.

The following TableSchemes are installed by default:

• JDBCTableScheme (scheme name="jdbc")
• LoopTableScheme (scheme name="loop")
• ClassTableScheme (scheme name="class")

Additionally, any classes named in the startable.schemes system property (as a colon-separated list) which implement the TableScheme interface and have a no-arg constructor will be instantiated and added to the known scheme list.

The factory has a flag requireRandom which determines whether the makeStarTable methods are guaranteed to return tables which provide random access (StarTable.isRandom()==true). NOTE the meaning (and name) of this flag has changed as of STIL version 2.1. Previously it was only a hint that random tables were preferred. Now setting it true guarantees that all tables returned by the factory are random.

Field Summary

Fields

Modifier and Type	Field and Description
static java.lang.String	AUTO_HANDLER Special handler identifier which signifies automatic format detection.
static java.lang.String	KNOWN_BUILDERS_PROPERTY System property which can contain a list of TableBuilder classnames for addition to the known (non-automatically detected) handler list.
static java.lang.String	SCHEMES_PROPERTY System property which can contain a list of TableScheme classnames for addition to the default list.

Constructor Summary

Constructors

Constructor and Description
StarTableFactory() Constructs a StarTableFactory with a default list of builders which is not guaranteed to construct random-access tables.
StarTableFactory(boolean requireRandom) Constructs a StarTableFactory with a default list of builders specifying whether it will return random-access tables.
StarTableFactory(StarTableFactory fact) Constructs a StarTableFactory which is a copy of an existing one.

Method Summary

Modifier and Type	Method and Description
void	addScheme(TableScheme scheme) Safely adds a table scheme for use by this factory.
boolean	canImport(java.awt.datatransfer.DataFlavor[] flavors) Indicates whether a particular set of DataFlavor ojects offered by a Transferable is suitable for attempting to turn the Transferable into a StarTable.
java.util.List<TableBuilder>	getDefaultBuilders() Gets the list of builders which are used for automatic format detection.
java.util.function.Predicate<DataSource>	getInputRestriction() Returns the object controlling access to input data.
JDBCHandler	getJDBCHandler() Returns the JDBC handler object used by this factory.
java.util.List<TableBuilder>	getKnownBuilders() Gets the list of builders which are available for selection by format name.
java.util.List<java.lang.String>	getKnownFormats() Returns the list of format names, one for each of the handlers returned by getKnownBuilders().
TablePreparation	getPreparation() Returns the current table preparation object, if any.
java.util.Map<java.lang.String,TableScheme>	getSchemes() Returns a schemeName->scheme map indicating the TableSchemes in use by this factory.
StoragePolicy	getStoragePolicy() Returns the current storage policy.
TableBuilder	getTableBuilder(java.lang.String name) Returns a table handler with a given name.
StarTable	makeStarTable(DataSource datsrc) Constructs a StarTable from a DataSource object using automatic format detection.
StarTable	makeStarTable(DataSource datsrc, java.lang.String handler) Constructs a StarTable from a DataSource using a named table input handler.
StarTable	makeStarTable(java.io.InputStream in, TableBuilder builder) Attempts to read and return a StarTable from an input stream.
StarTable	makeStarTable(java.lang.String location) Constructs a StarTable from a location string without format specification.
StarTable	makeStarTable(java.lang.String location, java.lang.String handler) Constructs a StarTable from a location string using a named table input handler.
StarTable	makeStarTable(java.awt.datatransfer.Transferable trans) Constructs a StarTable from a Transferable object using automatic format detection.
StarTable	makeStarTable(java.net.URL url) Deprecated. Use makeStarTable(new URLDataSource(url))
StarTable	makeStarTable(java.net.URL url, java.lang.String handler) Deprecated. Use makeStarTable(new URLDataSource(url),handler)
TableSequence	makeStarTables(DataSource datsrc) Constructs a sequence of StarTables from a DataSource using automatic format detection.
TableSequence	makeStarTables(DataSource datsrc, java.lang.String handler) Constructs a sequence of StarTables from a DataSource using a named table input handler.
TableSequence	makeStarTables(java.lang.String location, java.lang.String handler) Constructs a sequence of StarTables from a location string using a named table input handler.
static java.lang.String[]	parseSchemeLocation(java.lang.String location) Parses a scheme-format table specification as a scheme name and a scheme-specific part.
StarTable	randomTable(StarTable table) Returns a table based on a given table and guaranteed to have random access.
boolean	requireRandom() Returns the requireRandom flag.
void	setDefaultBuilders(TableBuilder[] builders) Sets the list of builders which actually do the table construction.
void	setInputRestriction(java.util.function.Predicate<DataSource> restriction) Sets an object that can control access to input data.
void	setJDBCHandler(JDBCHandler handler) Sets the JDBC handler object used by this factory.
void	setKnownBuilders(TableBuilder[] builders) Sets the list of builders which are available for selection by format name.
void	setPreparation(TablePreparation tablePrep) Sets a table preparation object that is invoked on each table created by this factory.
void	setRequireRandom(boolean requireRandom) Sets whether random-access tables will be constructed by this factory.
void	setStoragePolicy(StoragePolicy policy) Sets the storage policy.

Methods inherited from class java.lang.Object

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

Field Detail

KNOWN_BUILDERS_PROPERTY

public static final java.lang.String KNOWN_BUILDERS_PROPERTY

System property which can contain a list of TableBuilder classnames for addition to the known (non-automatically detected) handler list.

See Also:

Constant Field Values

SCHEMES_PROPERTY

public static final java.lang.String SCHEMES_PROPERTY

System property which can contain a list of TableScheme classnames for addition to the default list.

See Also:

Constant Field Values

AUTO_HANDLER

public static final java.lang.String AUTO_HANDLER

Special handler identifier which signifies automatic format detection.

See Also:

Constant Field Values

Constructor Detail

StarTableFactory

public StarTableFactory()

Constructs a StarTableFactory with a default list of builders which is not guaranteed to construct random-access tables.

StarTableFactory

public StarTableFactory(boolean requireRandom)

Constructs a StarTableFactory with a default list of builders specifying whether it will return random-access tables.

Parameters:

requireRandom - whether random-access tables will be constructed

StarTableFactory

public StarTableFactory(StarTableFactory fact)

Constructs a StarTableFactory which is a copy of an existing one.

Parameters:

fact - instance to copy

Method Detail

getDefaultBuilders

public java.util.List<TableBuilder> getDefaultBuilders()

Gets the list of builders which are used for automatic format detection. Builders earlier in the list are given a chance to make the table before ones later in the list. This list can be modified to change the behaviour of the factory.

Returns:

a mutable list of TableBuilder objects used to construct StarTables

setDefaultBuilders

public void setDefaultBuilders(TableBuilder[] builders)

Sets the list of builders which actually do the table construction. Builders earlier in the list are given a chance to make the table before ones later in the list.

Parameters:

builders - an array of TableBuilder objects used to construct StarTables

getKnownBuilders

public java.util.List<TableBuilder> getKnownBuilders()

Gets the list of builders which are available for selection by format name. This is initially set to the list of default builders plus a few others. This list can be modified to change the behaviour of the factory.

Returns:

a mutable list of TableBuilder objects which may be specified for table building

setKnownBuilders

public void setKnownBuilders(TableBuilder[] builders)

Sets the list of builders which are available for selection by format name. This is initially set to the list of default builders plus a few others.

Parameters:

builders - an array of TableBuilder objects used to construct StarTables

getKnownFormats

public java.util.List<java.lang.String> getKnownFormats()

Returns the list of format names, one for each of the handlers returned by getKnownBuilders().

Returns:

list of format name strings

getSchemes

public java.util.Map<java.lang.String,TableScheme> getSchemes()

Returns a schemeName->scheme map indicating the TableSchemes in use by this factory. This map is mutable, so entries may be added or removed, but NOTE that the map keys are assumed to be equivalent to the getSchemeName return value for their value, so modify it with care. Consider using the addScheme(uk.ac.starlink.table.TableScheme) method for adding entries.

Returns:

map of scheme names to schemes

addScheme

public void addScheme(TableScheme scheme)

Safely adds a table scheme for use by this factory. It is equivalent to getSchemes().put(scheme.getSchemeName(),scheme).

Parameters:

scheme - new scheme for use

setRequireRandom

public void setRequireRandom(boolean requireRandom)

Sets whether random-access tables will be constructed by this factory. If this flag is set true then any table returned by the various makeStarTable methods is guaranteed to provide random access (its StarTable.isRandom() method will return true). If the flag is false, then returned tables may or may not be random-access.

Parameters:

requireRandom - whether this factory will create random-access tables

requireRandom

public boolean requireRandom()

Returns the requireRandom flag. If this flag is set true then any table returned by the various makeStarTable methods is guaranteed to provide random access (its StarTable.isRandom() method will return true). If the flag is false, then returned tables may or may not be random-access.

Returns:

whether this factory will create random-access tables

setStoragePolicy

public void setStoragePolicy(StoragePolicy policy)

Sets the storage policy. This may be used to determine what kind of scratch storage is used when constructing tables.

Parameters:

policy - the new storage policy object

getStoragePolicy

public StoragePolicy getStoragePolicy()

Returns the current storage policy. This may be used to determine what kind of scratch storage is used when constructing tables. If it has not been set explicitly, the default policy is used (StoragePolicy.getDefaultPolicy()).

Returns:

storage policy object

setPreparation

public void setPreparation(TablePreparation tablePrep)

Sets a table preparation object that is invoked on each table created by this factory. Any previous value is overwritten. Null is allowed.

Parameters:

tablePrep - new table preparation, or null

getPreparation

public TablePreparation getPreparation()

Returns the current table preparation object, if any. By default, null is returned.

Returns:

table preparation, or null

setInputRestriction

public void setInputRestriction(java.util.function.Predicate<DataSource> restriction)

Sets an object that can control access to input data. If a non-null value is set, then any attempt to read a table from a resource such as a file or URL will first test it using the supplied predicate. If its test method returns false, the table read attempt will fail with an IOException.

Parameters:

restriction - policy for restricting DataSource access, or null for no restrictions

getInputRestriction

public java.util.function.Predicate<DataSource> getInputRestriction()

Returns the object controlling access to input data. By default this returns null, meaning no access controls.

Returns:

policy for restricting DataSource access, or null

See Also:

setInputRestriction(java.util.function.Predicate<uk.ac.starlink.util.DataSource>)

randomTable

public StarTable randomTable(StarTable table)
                      throws java.io.IOException

Returns a table based on a given table and guaranteed to have random access. If the original table table has random access then it is returned, otherwise a new random access table is built using its data.

This convenience method is equivalent to getStoragePolicy().randomTable(table).

Parameters:

table - original table

Returns:

a table with the same data as table and with isRandom()==true

Throws:

java.io.IOException

makeStarTable

public StarTable makeStarTable(DataSource datsrc)
                        throws TableFormatException,
                               java.io.IOException

Constructs a StarTable from a DataSource object using automatic format detection.

Parameters:

datsrc - the data source containing the table data

Returns:

a new StarTable view of the resource datsrc

Throws:

TableFormatException - if none of the default handlers could turn datsrc into a table

java.io.IOException - if an I/O error is encountered

makeStarTables

public TableSequence makeStarTables(DataSource datsrc)
                             throws TableFormatException,
                                    java.io.IOException

Constructs a sequence of StarTables from a DataSource using automatic format detection. Only certain formats (those whose handlers implement MultiTableBuilder) will be capable of returning a sequence having more than one element.

Parameters:

datsrc - the data source containing the table data

Returns:

a sequence of tables loaded from datsrc

Throws:

TableFormatException - if none of the default handlers could turn datsrc into a table

java.io.IOException - if an I/O error is encountered

makeStarTable

public StarTable makeStarTable(java.lang.String location)
                        throws TableFormatException,
                               java.io.IOException

Constructs a StarTable from a location string without format specification. The location string can represent a filename or URL, or a scheme-based specification of the form <scheme>:<scheme-spec> corresponding to one of the installed schemes.

Parameters:

location - the name of the table resource

Returns:

a new StarTable view of the resource at location

Throws:

TableFormatException - if no handler capable of turning location into a table is available

java.io.IOException - if one of the handlers encounters an error constructing a table

makeStarTable

@Deprecated
public StarTable makeStarTable(java.net.URL url)
                                    throws java.io.IOException

Deprecated. Use makeStarTable(new URLDataSource(url))

Constructs a StarTable from a URL using automatic format detection.

Parameters:

url - the URL where the table lives

Returns:

a new StarTable view of the resource at url

Throws:

TableFormatException - if no handler capable of turning datsrc into a table is available

java.io.IOException - if one of the handlers encounters an error constructing a table

makeStarTable

public StarTable makeStarTable(DataSource datsrc,
                               java.lang.String handler)
                        throws TableFormatException,
                               java.io.IOException

Constructs a StarTable from a DataSource using a named table input handler. The input handler may be named either using its format name (as returned from the TableBuilder.getFormatName() method) or by giving the full class name of the handler. In the latter case this factory does not need to have been informed about the handler previously. If null or the empty string or the special value AUTO_HANDLER is supplied for handler, it will fall back on automatic format detection.

Parameters:

datsrc - the data source containing the table data

handler - specifier for the handler which can handle tables of the right format

Returns:

a new StarTable view of the resource datsrc

Throws:

TableFormatException - if datsrc does not contain a table in the format named by handler

java.io.IOException - if an I/O error is encountered

makeStarTables

public TableSequence makeStarTables(DataSource datsrc,
                                    java.lang.String handler)
                             throws TableFormatException,
                                    java.io.IOException

Constructs a sequence of StarTables from a DataSource using a named table input handler. The input handler may be named either using its format name (as returned from the TableBuilder.getFormatName() method) or by giving the full class name of the handler. In the latter case this factory does not need to have been informed about the handler previously. If null or the empty string or the special value AUTO_HANDLER is supplied for handler, it will fall back on automatic format detection.

If the handler does not implement the MultiTableBuilder interface, then the returned sequence will contain a single table.

Parameters:

datsrc - the data source containing the table data

handler - specifier for the handler which can handle tables of the right format

Returns:

a sequence of StarTables loaded from datsrc

Throws:

TableFormatException - if datsrc does not contain a table in the format named by handler

java.io.IOException - if an I/O error is encountered

makeStarTables

public TableSequence makeStarTables(java.lang.String location,
                                    java.lang.String handler)
                             throws TableFormatException,
                                    java.io.IOException

Constructs a sequence of StarTables from a location string using a named table input handler. The input handler may be named either using its format name (as returned from the TableBuilder.getFormatName() method) or by giving the full class name of the handler. In the latter case this factory does not need to have been informed about the handler previously. If null or the empty string or the special value AUTO_HANDLER is supplied for handler, it will fall back on automatic format detection.

Alternatively, the location string can be a scheme-based specification, in which case the handler is ignored.

Parameters:

location - the name of the table resource

handler - specifier for the handler which can handle tables of the right format

Returns:

a new StarTable view of the resource at location

Throws:

TableFormatException - if location does not point to a table in the format named by handler

java.io.IOException - if an I/O error is encountered

makeStarTable

public StarTable makeStarTable(java.lang.String location,
                               java.lang.String handler)
                        throws TableFormatException,
                               java.io.IOException

Constructs a StarTable from a location string using a named table input handler. The input handler may be named either using its format name (as returned from the TableBuilder.getFormatName() method) or by giving the full class name of the handler. In the latter case this factory does not need to have been informed about the handler previously. If null or the empty string or the special value AUTO_HANDLER is supplied for handler, it will fall back on automatic format detection.

A location of "-" means standard input - in this case the handler must be specified.

Alternatively, the location string can be a scheme-based specification, in which case the handler is ignored.

Parameters:

location - the name of the table resource

handler - specifier for the handler which can handle tables of the right format

Returns:

a new StarTable view of the resource at location

Throws:

TableFormatException - if location does not point to a table in the format named by handler

java.io.IOException - if an I/O error is encountered

makeStarTable

@Deprecated
public StarTable makeStarTable(java.net.URL url,
                                           java.lang.String handler)
                                    throws TableFormatException,
                                           java.io.IOException

Deprecated. Use makeStarTable(new URLDataSource(url),handler)

Constructs a StarTable from a URL using a named table input handler. The input handler may be named either using its format name (as returned from the TableBuilder.getFormatName() method) or by giving the full class name of the handler. In the latter case this factory does not need to have been informed about the handler previously. If null or the empty string or the special value AUTO_HANDLER is supplied for handler, it will fall back on automatic format detection.

Parameters:

url - the URL where the table lives

handler - specifier for the handler which can handle tables of the right format

Returns:

a new StarTable view of the resource at url

Throws:

TableFormatException - if the resource at url cannot be turned into a table by handler

java.io.IOException - if an I/O error is encountered

makeStarTable

public StarTable makeStarTable(java.io.InputStream in,
                               TableBuilder builder)
                        throws TableFormatException,
                               java.io.IOException

Attempts to read and return a StarTable from an input stream. This is not always possible, since certain table handlers may required more than one pass through the input data. The handler must be specified (automatic format detection cannot be used on a stream). The input stream will be decompressed and buffered if necessary.

Parameters:

in - input stream

builder - handler which understands the data in in

Returns:

a table read from the stream if it could be done

Throws:

TableFormatException - if builder needs more than one pass of the data, or the stream is in some way malformed

java.io.IOException - for other I/O errors

See Also:

TableBuilder.streamStarTable(java.io.InputStream, uk.ac.starlink.table.TableSink, java.lang.String)

makeStarTable

public StarTable makeStarTable(java.awt.datatransfer.Transferable trans)
                        throws java.io.IOException

Constructs a StarTable from a Transferable object using automatic format detection. In conjunction with a suitable TransferHandler this makes it easy to accept drop of an object representing a table which has been dragged from another application.

The implementation of this method currently tries the following on a given transferable to turn it into a table:

• If it finds a URL object, passes that to the URL factory method
• If it finds a transferable that will supply an InputStream, turns it into a DataSource and passes that to the DataSource constructor

Parameters:

trans - the Transferable object to construct a table from

Returns:

a new StarTable constructed from the Transferable

Throws:

TableFormatException - if no table can be constructed

java.io.IOException

See Also:

canImport(java.awt.datatransfer.DataFlavor[])

canImport

public boolean canImport(java.awt.datatransfer.DataFlavor[] flavors)

Indicates whether a particular set of DataFlavor ojects offered by a Transferable is suitable for attempting to turn the Transferable into a StarTable.

Each of the builder objects is queried about whether it can import the given flavour, and if one says it can, a true value is returned. A true value is also returned if one of the flavours has a representation class of URL.

Parameters:

flavors - the data flavours offered

getJDBCHandler

public JDBCHandler getJDBCHandler()

Returns the JDBC handler object used by this factory.

Returns:

the JDBC handler

setJDBCHandler

public void setJDBCHandler(JDBCHandler handler)

Sets the JDBC handler object used by this factory.

Parameters:

handler - the JDBC handler

getTableBuilder

public TableBuilder getTableBuilder(java.lang.String name)
                             throws TableFormatException

Returns a table handler with a given name. This name may be either its format name (as returned from the TableBuilder.getFormatName() method) or by giving the full class name of the handler. In the latter case this factory does not need to have been informed about the handler previously.

Parameters:

name - specification of the handler required

Returns:

TableBuilder specified by name

Throws:

TableFormatException - if name doesn't name any available handler

parseSchemeLocation

public static java.lang.String[] parseSchemeLocation(java.lang.String location)

Parses a scheme-format table specification as a scheme name and a scheme-specific part. Normally schemes are of the form ":<scheme-name>:<scheme-specific-part>", but as a special case the initial colon may be omitted for JDBC (backward compatibility).

Parameters:

location - table specification

Returns:

if the location is syntactically a scheme, a 2-element array giving [scheme-name,scheme-specific-part]; otherwise null