Interface TableBuilder
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- All Known Subinterfaces:
MultiTableBuilder
- All Known Implementing Classes:
AsciiTableBuilder
,CoinsTableBuilder
,CsvTableBuilder
,IpacTableBuilder
,TstTableBuilder
,WDCTableBuilder
public interface TableBuilder
Interface for objects which can construct a StarTable from a data resource. TableBuilder implementations may also choose to implementMultiTableBuilder
.- Author:
- Mark Taylor (Starlink)
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Method Summary
All Methods Instance Methods Abstract Methods Modifier and Type Method Description boolean
canImport(java.awt.datatransfer.DataFlavor flavor)
Indicates whether this builder is able to turn a resource of media type indicated by flavor into a table.java.lang.String
getFormatName()
Returns the name of the format which can be read by this handler.StarTable
makeStarTable(uk.ac.starlink.util.DataSource datsrc, boolean wantRandom, StoragePolicy storagePolicy)
Constructs aStarTable
based on a given DataSource.void
streamStarTable(java.io.InputStream istrm, TableSink sink, java.lang.String pos)
Reads a table from an input stream and writes it a row at a time to a sink.
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Method Detail
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makeStarTable
StarTable makeStarTable(uk.ac.starlink.util.DataSource datsrc, boolean wantRandom, StoragePolicy storagePolicy) throws java.io.IOException
Constructs aStarTable
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 aTableFormatException
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 suppliedstoragePolicy
, or any other resource-expensive measure, to randomise a sequential table just because thewantRandom
parameter is true.- Parameters:
datsrc
- the DataSource containing the table resourcewantRandom
- whether, preferentially, a random access table should be returnedstoragePolicy
- 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 handlerjava.io.IOException
- if an unexpected I/O error occurs during processing
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streamStarTable
void streamStarTable(java.io.InputStream istrm, TableSink sink, java.lang.String pos) throws java.io.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 aTableFormatException
.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 datasink
- destination of the tablepos
- position identifier describing the location of the table within the stream; seeDataSource.getPosition()
(may be null)- Throws:
TableFormatException
- if the table can't be streamed or the data is malformedjava.io.IOException
- if some other error occurs
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canImport
boolean canImport(java.awt.datatransfer.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 itsstreamStarTable(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 theDataFlavor
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
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getFormatName
java.lang.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
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