Class StarTableOutput

java.lang.Object
uk.ac.starlink.table.StarTableOutput

public class StarTableOutput extends Object
Outputs StarTable objects. This object delegates the actual writing to one of a list of format-specific writer objects whose content can be configured externally. By default, if the corresponding classes are present, the following handlers are installed: Additionally, any classes named in the startable.writers system property (as a colon-separated list) which implement the StarTableWriter interface and have a no-arg constructor will be instantiated and added to this list of handlers.

It can additionally write to JDBC tables.

Author:
Mark Taylor (Starlink)
  • Field Details

    • AUTO_HANDLER

      public static final String AUTO_HANDLER
      Special output handler name indicating automatic format selection.
      See Also:
    • EXTRA_WRITERS_PROPERTY

      public static final String EXTRA_WRITERS_PROPERTY
      System property which can contain a list of StarTableWriter classes for addition to the list of known output handlers.
      See Also:
  • Constructor Details

    • StarTableOutput

      public StarTableOutput()
      Constructs a StarTableOutput with a default list of handlers.
  • Method Details

    • getHandlers

      public List<StarTableWriter> getHandlers()
      Gets the list of handlers which can actually do table output. Handlers earlier in the list are given a chance to write the table before ones later in the list. The returned list may be modified to change this object's behaviour.
      Returns:
      handlers a list of StarTableWriter objects
    • setHandlers

      public void setHandlers(StarTableWriter[] handlers)
      Sets the list of handlers which can actually do table output. Handlers earlier in the list are given a chance to write the table before ones later in the list.
      Parameters:
      handlers - an array of StarTableWriter objects
    • writeStarTable

      public void writeStarTable(StarTable startab, String location, String format) throws TableFormatException, IOException
      Writes a StarTable object out to some external storage. The format in which it is written is determined by some combination of the given output location and a format indicator.
      Parameters:
      startab - the table to output
      location - the location at which to write the new table. This may be a filename or URL, including a jdbc: protocol if suitable JDBC drivers are installed
      format - a string which indicates in some way what format should be used for output. This may be the class name of a StarTableWriter object (which may or may not be registered with this StarTableOutput), or else a string which matches the format name of one of the registered StarTableWriters (first match is used, case-insensitive, starting substrings OK) or null or AUTO_HANDLER to indicate that a handler should be selected based on the value of location. Ignored for jdbc:-protocol locations
      Throws:
      TableFormatException - if no suitable handler is known
      IOException
    • writeStarTable

      public void writeStarTable(StarTable startab, OutputStream out, StarTableWriter handler) throws IOException
      Writes a StarTable to an output stream. This convenience method wraps the stream in a BufferedOutputStream for efficiency and uses the submitted handler to perform the write, closing the stream afterwards.
      Parameters:
      startab - table to write
      out - raw output stream
      handler - output handler
      Throws:
      IOException
      See Also:
    • writeStarTables

      public void writeStarTables(StarTable[] tables, String location, String format) throws TableFormatException, IOException
      Writes an array of StarTable objects to some external storage. The format in which they are written is determined by some combination of the given output location and a format indicator. Note that not all registered output handlers are capable of writing multiple tables; an exception will be thrown if an attempt is made to write multiple tables with a handler which does not implement MultiStarTableWriter.
      Parameters:
      tables - the tables to output
      location - the location at which to write the tables; this may be a filename or URL
      format - a string which indicates in some way what format should be used for output. This may be the class name of a MultiStarTableWriter object (which may or may not be registered with this StarTableOutput), or else a string which matches the format name of one of the registered MultiStarTableWriters (first match is used, case-insensitive, starting substrings OK) or null or AUTO_HANDLER to indicate that a handler should be selected based on the value of location.
      Throws:
      TableFormatException
      IOException
    • writeStarTables

      public void writeStarTables(StarTable[] tables, OutputStream out, MultiStarTableWriter handler) throws IOException
      Writes an array of StarTables to an output stream. This convenience method wraps the stream in a BufferedOutputStream for efficiency and uses the submitted handler to perform the write, closing the stream afterwards.
      Parameters:
      tables - tables to write
      out - destination stream
      handler - output handler
      Throws:
      IOException
    • createOutputSink

      public TableSink createOutputSink(OutputStream out, StarTableWriter handler)
      Returns a sink which allows you to write data to an output table. Note that this will only work if the handler can write the table using a single pass of the data. If it requires multiple passes, a UnrepeatableSequenceException will be thrown.
      Parameters:
      out - raw output stream
      handler - output handler
      Returns:
      sink whose data will be written to a new table
    • createOutputSink

      public TableSink createOutputSink(String location, String format)
      Returns a sink which allows you to write data to an output table. Note that this will only work if the handler can write the table using a single pass of the data. If it requires multiple passes, a UnrepeatableSequenceException will be thrown.
      Parameters:
      location - the location at which to write the new table. This may be a filename or URL, including a jdbc: protocol if suitable JDBC drivers are installed
      format - a string which indicates in some way what format should be used for output. This may be the class name of a StarTableWriter object (which may or may not be registered with this StarTableOutput), or else a string which matches the format name of one of the registered StarTableWriters (first match is used, case-insensitive, starting substrings OK) or null or AUTO_HANDLER to indicate that a handler should be selected based on the value of location. Ignored for jdbc:-protocol locations
      Returns:
      sink whose data will be written to a new table
    • getOutputStream

      public OutputStream getOutputStream(String location) throws IOException
      Returns an output stream which points to a given location. Typically location is a filename and a corresponding FileOutputStream is returned, but there may be other possibilities. The stream returned by this method will not in general be buffered; for high performance writes, wrapping it in a BufferedOutputStream may be a good idea.
      Parameters:
      location - name of destination
      Returns:
      output stream which writes to location
      Throws:
      IOException - if no stream pointing to location can be opened
    • getHandler

      public StarTableWriter getHandler(String format) throws TableFormatException
      Returns a StarTableWriter object given an output format name.
      Parameters:
      format - a string which indicates in some way what format should be used for output. This may be the class name of a StarTableWriter object (which may or may not be registered with this StarTableOutput), or else a string which matches the format name of one of the registered StarTableWriters (first match is used, case-insensitive, starting substrings OK).
      Returns:
      a suitable output handler
      Throws:
      TableFormatException - if no handler suitable for the arguments can be found
    • getHandler

      public StarTableWriter getHandler(String format, String location) throws TableFormatException
      Returns a StarTableWriter object given an output format name and/or a location to write to. If the format name is blank, the location is used to guess the type of output required.
      Parameters:
      format - a string which indicates in some way what format should be used for output. This may be the class name of a StarTableWriter object (which may or may not be registered with this StarTableOutput), or else a string which matches the format name of one of the registered StarTableWriters (first match is used, case-insensitive, starting substrings OK) or null to indicate that a handler should be selected based on the value of location.
      location - destination of the table to be written. If format is null, the value of this will be used to try to determine which handler to use, typically on the basis of filename extension
      Returns:
      a suitable output handler
      Throws:
      TableFormatException - if no handler suitable for the arguments can be found
    • getKnownFormats

      public List<String> getKnownFormats()
      Returns a list of the format strings which are defined by the handlers registered with this object. The elements of the returned list can be passed as the format argument to the writeStarTable(uk.ac.starlink.table.StarTable, java.lang.String, java.lang.String) method.
    • getJDBCHandler

      public JDBCHandler getJDBCHandler()
      Returns the JDBCHandler object used for writing tables to JDBC connections.
      Returns:
      the JDBC handler
    • setJDBCHandler

      public void setJDBCHandler(JDBCHandler handler)
      Sets the JDBCHandler object used for writing tables to JDBC connections.
      Parameters:
      handler - the handler to use
    • transferStarTable

      public Transferable transferStarTable(StarTable startab)
      Returns a Transferable object associated with a given StarTable, for use at the drag end of a drag and drop operation.
      Parameters:
      startab - the table which is to be dragged
      See Also: