Interface TableBuilder

All Known Subinterfaces:
MultiTableBuilder
All Known Implementing Classes:
AsciiTableBuilder, CoinsTableBuilder, CsvTableBuilder, DocumentedTableBuilder, IpacTableBuilder, MrtTableBuilder, TstTableBuilder, VerTableBuilder, WDCTableBuilder

public interface TableBuilder
Interface for objects which can construct a StarTable from a data resource. TableBuilder implementations may also choose to implement MultiTableBuilder.
Author:
Mark Taylor (Starlink)
  • Method Summary

    Modifier and Type
    Method
    Description
    boolean
    Indicates whether this builder is able to turn a resource of media type indicated by flavor into a table.
    Returns the name of the format which can be read by this handler.
    boolean
    Indicates whether the given location string is of a familiar form for this builder.
    makeStarTable(uk.ac.starlink.util.DataSource datsrc, boolean wantRandom, StoragePolicy storagePolicy)
    Constructs a StarTable based on a given DataSource.
    void
    Reads a table from an input stream and writes it a row at a time to a sink.
  • Method Details

    • makeStarTable

      StarTable makeStarTable(uk.ac.starlink.util.DataSource datsrc, boolean wantRandom, StoragePolicy storagePolicy) throws IOException
      Constructs a StarTable based on a given DataSource. If the source is not recognised or this builder does not know how to construct a table from it, then a TableFormatException should be thrown. If this builder thinks it should be able to handle the source but an error occurs during processing, an IOException can be thrown.

      The wantRandom parameter is used to indicate whether, ideally, a random-access table should be returned. There is no requirement for the builder to honour this request, but if it knows how to make both random and non-random tables, it can use this flag to decide which to return.

      Note: the presence of the wantRandom parameter is somewhat misleading. TableBuilder implementations usually should, and do, ignore it (it would be removed from the interface if it were not for backward compatibility issues). Regardless of the value of this parameter, implementations should return a random-access table only if it is easy for them to do so; in particular they should not use the supplied storagePolicy, or any other resource-expensive measure, to randomise a sequential table just because the wantRandom parameter is true.

      Parameters:
      datsrc - the DataSource containing the table resource
      wantRandom - whether, preferentially, a random access table should be returned
      storagePolicy - a StoragePolicy object which may be used to supply scratch storage if the builder needs it
      Returns:
      a StarTable made out of datsrc
      Throws:
      TableFormatException - if the table is not of a kind that can be handled by this handler
      IOException - if an unexpected I/O error occurs during processing
    • streamStarTable

      void streamStarTable(InputStream istrm, TableSink sink, String pos) throws IOException
      Reads a table from an input stream and writes it a row at a time to a sink. Not all implementations will be able to do this; for instance, extracting the table from the data may be a two-pass process. Implementations which are unable to perform this function should throw a TableFormatException.

      The input stream should be prepared for use prior to calling this method, so implementations should not in general attempt to decompress or buffer istrm.

      Parameters:
      istrm - input stream containing table data
      sink - destination of the table
      pos - position identifier describing the location of the table within the stream; see DataSource.getPosition() (may be null)
      Throws:
      TableFormatException - if the table can't be streamed or the data is malformed
      IOException - if some other error occurs
    • canImport

      boolean canImport(DataFlavor flavor)
      Indicates whether this builder is able to turn a resource of media type indicated by flavor into a table. It should return true if it thinks that its streamStarTable(java.io.InputStream, uk.ac.starlink.table.TableSink, java.lang.String) method stands a reasonable chance of successfully constructing a StarTable from a DataSource whose input stream is described by the DataFlavor flavor. It will typically make this determination based on the flavor's MIME type.

      This method should only return true if the flavor looks like it is targeted at this builder; for instance a builder which uses a text-based format should return false for a flavor which indicates a MIME type of text/plain.

      This method is used in supporting drag and drop functionality (see StarTableFactory.canImport(java.awt.datatransfer.DataFlavor[])).

      Parameters:
      flavor - the DataFlavor whose suitability as stream input is to be assessed
      Returns:
      true iff this builder reckons it stands a good chance of turning a stream of type flavor into a StarTable
    • looksLikeFile

      boolean looksLikeFile(String location)
      Indicates whether the given location string is of a familiar form for this builder. Implementations should return true if there is a good chance that a file with the given location can be interpreted by this reader, for instance if it has a suitable file extension.

      This method may be used to guess, on a best-efforts basis, whether this builder is suitable for reading a file from a given location. Attempts may still be made to read inputs for which this method returns false. It is less important for builders that can recognise files by magic number, which is generally preferable to using filenames.

      Parameters:
      location - the location string, such as a filename or URL (not null)
      Returns:
      true iff there is a good chance that the named input can be interpreted by this reader
    • getFormatName

      String getFormatName()
      Returns the name of the format which can be read by this handler. Matching against this string may be used by callers to identify or select this handler from a list.
      Returns:
      one-word description of this handler's format