net.sf.saxon.sort
Class SortKeyDefinition

java.lang.Object
  net.sf.saxon.sort.SortKeyDefinition

All Implemented Interfaces:

Serializable

public class SortKeyDefinition
extends Object
implements Serializable

A SortKeyDefinition defines one component of a sort key.
Note that most attributes defining the sort key can be attribute value templates, and can therefore vary from one invocation to another. We hold them as expressions. As soon as they are all known (which in general is only at run-time), the SortKeyDefinition is replaced by a FixedSortKeyDefinition in which all these values are fixed.

See Also:

Serialized Form

Constructor Summary

SortKeyDefinition()

Method Summary

String	getBaseURI()
Expression	getCaseOrder()
StringCollator	getCollation() Get the collation to be used
Expression	getCollationNameExpression() Get the selected collation name (specifically, an expression which when evaluated returns the collation URI).
Expression	getDataTypeExpression()
boolean	getEmptyLeast() Discover whether empty sequence comes before other values or after them
AtomicComparer	getFinalComparator() Get the comparator which is used to compare two values according to this sort key.
Expression	getLanguage()
Expression	getOrder()
Container	getParentExpression()
Expression	getSortKey() Get the expression used as the sort key
Expression	getStable()
boolean	isBackwardsCompatible()
boolean	isFixed() Discover whether the sort key definition is fixed, that is, whether all the information needed to create a Comparator is known statically
AtomicComparer	makeComparator(XPathContext context) Allocate an AtomicComparer to perform the comparisons described by this sort key component.
void	setBackwardsCompatible(boolean compatible)
void	setBaseURI(String baseURI)
void	setCaseOrder(Expression exp) Set the case order.
void	setCollation(StringCollator collation) Set the collation to be used
void	setCollationNameExpression(Expression collationName) Set the collation name (specifically, an expression which when evaluated returns the collation URI).
void	setDataTypeExpression(Expression exp) Set the data type.
void	setEmptyLeast(boolean emptyLeast) Set whether empty sequence comes before other values or after them
void	setFinalComparator(AtomicComparer comp) Set the comparator which is used to compare two values according to this sort key.
void	setLanguage(Expression exp) Set the language.
void	setOrder(Expression exp) Set the order.
void	setParentExpression(Container container)
void	setSortKey(Expression exp) Set the expression used as the sort key
void	setStable(Expression stable)
SortKeyDefinition	simplify(StaticContext env, Executable exec)

Methods inherited from class java.lang.Object

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

Constructor Detail

SortKeyDefinition

public SortKeyDefinition()

Method Detail

setParentExpression

public void setParentExpression(Container container)

getParentExpression

public Container getParentExpression()

setSortKey

public void setSortKey(Expression exp)

Set the expression used as the sort key

getSortKey

public Expression getSortKey()

Get the expression used as the sort key

setOrder

public void setOrder(Expression exp)

Set the order. This is supplied as an expression which must evaluate to "ascending" or "descending". If the order is fixed, supply e.g. new StringValue("ascending"). Default is "ascending".

getOrder

public Expression getOrder()

setDataTypeExpression

public void setDataTypeExpression(Expression exp)

Set the data type. This is supplied as an expression which must evaluate to "text", "number", or a QName. If the data type is fixed, the valus should be supplied using setDataType() and not via this method.

getDataTypeExpression

public Expression getDataTypeExpression()

setCaseOrder

public void setCaseOrder(Expression exp)

Set the case order. This is supplied as an expression which must evaluate to "upper-first" or "lower-first" or "#default". If the order is fixed, supply e.g. new StringValue("lower-first"). Default is "#default".

getCaseOrder

public Expression getCaseOrder()

setLanguage

public void setLanguage(Expression exp)

Set the language. This is supplied as an expression which evaluates to the language name. If the order is fixed, supply e.g. new StringValue("de").

getLanguage

public Expression getLanguage()

setCollationNameExpression

public void setCollationNameExpression(Expression collationName)

Set the collation name (specifically, an expression which when evaluated returns the collation URI).

getCollationNameExpression

public Expression getCollationNameExpression()

Get the selected collation name (specifically, an expression which when evaluated returns the collation URI).

setCollation

public void setCollation(StringCollator collation)

Set the collation to be used

Parameters:

collation - A NamedCollation, which encapsulates both the collation URI and the collating function

getCollation

public StringCollator getCollation()

Get the collation to be used

Returns:

A NamedCollation, which encapsulates both the collation URI and the collating function

setBaseURI

public void setBaseURI(String baseURI)

getBaseURI

public String getBaseURI()

setStable

public void setStable(Expression stable)

getStable

public Expression getStable()

setBackwardsCompatible

public void setBackwardsCompatible(boolean compatible)

isBackwardsCompatible

public boolean isBackwardsCompatible()

setEmptyLeast

public void setEmptyLeast(boolean emptyLeast)

Set whether empty sequence comes before other values or after them

Parameters:

emptyLeast - true if () is considered lower than any other value

getEmptyLeast

public boolean getEmptyLeast()

Discover whether empty sequence comes before other values or after them

Returns:

true if () is considered lower than any other value

isFixed

public boolean isFixed()

Discover whether the sort key definition is fixed, that is, whether all the information needed to create a Comparator is known statically

simplify

public SortKeyDefinition simplify(StaticContext env,
                                  Executable exec)
                           throws XPathException

Throws:

XPathException

makeComparator

public AtomicComparer makeComparator(XPathContext context)
                              throws XPathException

Allocate an AtomicComparer to perform the comparisons described by this sort key component. This method is called at run-time. The AtomicComparer takes into account not only the collation, but also parameters such as order=descending and handling of empty sequence and NaN (the result of the compare() method of the comparator is +1 if the second item is to sort after the first item)

Returns:

an AtomicComparer suitable for making the sort comparisons

Throws:

XPathException

setFinalComparator

public void setFinalComparator(AtomicComparer comp)

Set the comparator which is used to compare two values according to this sort key. The comparator makes the final decision whether one value sorts before or after another: this takes into account the data type, the collation, whether empty comes first or last, whether the sort order is ascending or descending.

This method is called at compile time if all these factors are known at compile time. It must not be called at run-time, except to reconstitute a finalComparator that has been lost by virtue of serialization .

getFinalComparator

public AtomicComparer getFinalComparator()

Get the comparator which is used to compare two values according to this sort key. This method may be called either at compile time or at run-time. If no comparator has been allocated, it returns null. It is then necessary to allocate a comparator using the makeComparator(net.sf.saxon.expr.XPathContext) method.