uk.ac.starlink.ttools.jel
Class JELTable

java.lang.Object
  extended by uk.ac.starlink.table.WrapperStarTable
      extended by uk.ac.starlink.ttools.jel.JELTable
All Implemented Interfaces:
StarTable

public class JELTable
extends WrapperStarTable

Wrapper table which is constructed entirely of columns defined by JEL expressions based on the base table.

Since:
1 Sep 2005
Author:
Mark Taylor

Field Summary
 
Fields inherited from class uk.ac.starlink.table.WrapperStarTable
baseTable
 
Constructor Summary
JELTable(StarTable baseTable, ColumnInfo[] colInfos, String[] exprs)
          Constructor.
 
Method Summary
static StarTable createJELTable(StarTable baseTable, ValueInfo[] infos, String[] exprs)
          Convenience factory method.
 Object getCell(long irow, int icol)
          Returns the contents of a given table cell.
 int getColumnCount()
          Returns the number of columns in this table.
 ColumnInfo getColumnInfo(int icol)
          Returns the object describing the data in a given column.
 Object[] getRow(long irow)
          Returns the contents of a given table row.
 RowSequence getRowSequence()
          Returns an object which can iterate over all the rows in the table sequentially.
 
Methods inherited from class uk.ac.starlink.table.WrapperStarTable
checkedLongToInt, getBaseTable, getColumnAuxDataInfos, getName, getParameterByName, getParameters, getRowCount, getURL, isRandom, setName, setParameter, setURL, toString
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

Constructor Detail

JELTable

public JELTable(StarTable baseTable,
                ColumnInfo[] colInfos,
                String[] exprs)
         throws gnu.jel.CompilationException
Constructor. The number of columns is the same as the number of elements of colInfos, which must be the same as the number of elements in exprs. If the contentClass attributes of the colInfos elements are non-null, they must be compatible with the actual types of the evaluated expressions. If they are not, an IllegalArgumentException will be thrown.

Parameters:
baseTable - table which provides both behaviour determining whether random access is available etc, and an evaluation context for the JEL calculations
colInfos - column metadata for each of the columns in this table
exprs - JEL expressions, evaluated in a context determined by baseTable, which give the data for this table.
Throws:
gnu.jel.CompilationException
Method Detail

getColumnCount

public int getColumnCount()
Description copied from interface: StarTable
Returns the number of columns in this table.

Specified by:
getColumnCount in interface StarTable
Overrides:
getColumnCount in class WrapperStarTable
Returns:
the number of columns

getColumnInfo

public ColumnInfo getColumnInfo(int icol)
Description copied from interface: StarTable
Returns the object describing the data in a given column.

Specified by:
getColumnInfo in interface StarTable
Overrides:
getColumnInfo in class WrapperStarTable
Parameters:
icol - the column for which header information is required
Returns:
a ValueInfo object for column icol

getCell

public Object getCell(long irow,
                      int icol)
               throws IOException
Description copied from interface: StarTable
Returns the contents of a given table cell. The class of the returned object should be the same as, or a subclass of, the class returned by getColumnInfo(icol).getContentClass().

Specified by:
getCell in interface StarTable
Overrides:
getCell in class WrapperStarTable
Parameters:
irow - the index of the cell's row
icol - the index of the cell's column
Returns:
the contents of this cell
Throws:
IOException - if there is an error reading the data

getRow

public Object[] getRow(long irow)
                throws IOException
Description copied from interface: StarTable
Returns the contents of a given table row. The returned value is equivalent to an array formed of all the objects returned by getCell(irow,icol) for all the columns icol in sequence.

Specified by:
getRow in interface StarTable
Overrides:
getRow in class WrapperStarTable
Parameters:
irow - the index of the row to retrieve
Returns:
an array of the objects in each cell in row irow
Throws:
IOException - if there is an error reading the data

getRowSequence

public RowSequence getRowSequence()
                           throws IOException
Description copied from interface: StarTable
Returns an object which can iterate over all the rows in the table sequentially.

Specified by:
getRowSequence in interface StarTable
Overrides:
getRowSequence in class WrapperStarTable
Returns:
an object providing sequential access to the table data
Throws:
IOException - if there is an error providing access

createJELTable

public static StarTable createJELTable(StarTable baseTable,
                                       ValueInfo[] infos,
                                       String[] exprs)
                                throws ExecutionException
Convenience factory method. It turns all the supplied infos into ColumnInfos and rethrows any CompilationException as an ExecutionException.

Parameters:
baseTable - table which provides both behaviour determining whether random access is available etc, and an evaluation context for the JEL calculations
infos - metadata used to construct column metadata
exprs - JEL expressions, evaluated in a context determined by baseTable, which give the data for this table.
Throws:
ExecutionException


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