uk.ac.starlink.ttools.jel

Class RandomJELRowReader

java.lang.Object

gnu.jel.DVMap

uk.ac.starlink.ttools.jel.JELRowReader

uk.ac.starlink.ttools.jel.StarTableJELRowReader

uk.ac.starlink.ttools.jel.RandomJELRowReader

public abstract class RandomJELRowReader
extends StarTableJELRowReader

Provides JELRowReader functionality for a random access table. This abstract class adds the abstract method evaluateAtRow(gnu.jel.CompiledExpression, long); factory methods are provided to implement this in different ways according to the requirements of multi-threaded usage.

Since:

8 Feb 2005

Author:

Mark Taylor (Starlink)

Field Summary

Fields inherited from class uk.ac.starlink.ttools.jel.StarTableJELRowReader

PARAM_PREFIX, UCD_PREFIX, UTYPE_PREFIX

Fields inherited from class uk.ac.starlink.ttools.jel.JELRowReader

COLUMN_ID_CHAR, NULL_QUERY_PREFIX, OBJECT_PREFIX

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	RandomJELRowReader(StarTable table) Constructor.

Method Summary

Modifier and Type	Method and Description
static RandomJELRowReader	createAccessReader(StarTable table) Convenience method that obtains and uses a RowAccess from a given table.
static RandomJELRowReader	createAccessReader(StarTable table, RowAccess racc) Returns an instance that uses a RowAccess object from the table for supplying data values.
static RandomJELRowReader	createConcurrentReader(StarTable table) Returns an instance that uses the threadsafe random access methods of the supplied table.
abstract Object	evaluateAtRow(gnu.jel.CompiledExpression compEx, long lrow) Evaluates a given compiled expression at a given row.

Methods inherited from class uk.ac.starlink.ttools.jel.StarTableJELRowReader

createDescribedValueConstant, getBooleanColumnValue, getByteColumnValue, getCell, getCharColumnValue, getColumnClass, getColumnIndexByName, getConstantByName, getCurrentRow, getDescribedValueByName, getDoubleColumnValue, getFloatColumnValue, getIntColumnValue, getLongColumnValue, getObjectColumnValue, getShortColumnValue, getSpecialByName, getTable, getUcdRegex, getUtypeRegex, isBlank, requiresRowIndex, valueDouble, valueInt, valueLong, valueObject, valueString

Methods inherited from class uk.ac.starlink.ttools.jel.JELRowReader

evaluate, evaluateBoolean, evaluateDouble, foundNull, getBooleanArrayProperty, getBooleanProperty, getBooleanProperty, getBooleanValue, getByteArrayProperty, getByteProperty, getByteValue, getCharArrayProperty, getCharProperty, getCharValue, getColumnIndex, getDateArrayProperty, getDoubleArrayProperty, getDoubleProperty, getDoubleValue, getFloatArrayProperty, getFloatProperty, getFloatValue, getIntArrayProperty, getIntProperty, getIntValue, getLongArrayProperty, getLongProperty, getLongValue, getNumberProperty, getObjectArrayProperty, getObjectProperty, getShortArrayProperty, getShortProperty, getShortValue, getStringArrayProperty, getStringProperty, getTranslatedColumns, getTranslatedConstants, getTypeName, setFailOnNull, stripPrefix, translate

Methods inherited from class java.lang.Object

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

Constructor Detail

RandomJELRowReader

protected RandomJELRowReader(StarTable table)

Constructor.

Parameters:

table - table object

Method Detail

evaluateAtRow

public abstract Object evaluateAtRow(gnu.jel.CompiledExpression compEx,
                                     long lrow)
                              throws Throwable

Evaluates a given compiled expression at a given row. The returned value is wrapped up as an object if the result of the expression is a primitive.

Parameters:

compEx - compiled expression

lrow - row index

Returns:

expression result as an object

Throws:

Throwable

createConcurrentReader

public static RandomJELRowReader createConcurrentReader(StarTable table)

Returns an instance that uses the threadsafe random access methods of the supplied table. The random access methods of the returned object are synchronized, so that although it is safe for use from multiple threads, it may not be efficient.

Parameters:

table - supplies data

Returns:

row reader

createAccessReader

public static RandomJELRowReader createAccessReader(StarTable table,
                                                    RowAccess racc)

Returns an instance that uses a RowAccess object from the table for supplying data values. This is only suitable for use from a single thread.

Parameters:

table - table object

racc - row access previously obtained from table

Returns:

row reader

createAccessReader

public static RandomJELRowReader createAccessReader(StarTable table)
                                             throws IOException

Convenience method that obtains and uses a RowAccess from a given table. Note it is not possible to close the RowAccess in this case.

Parameters:

table - table object

Returns:

result of createAccessReader(table,table.getRowAccess())

Throws:

IOException