org.exist.xquery
Class Function

java.lang.Object
  org.exist.xquery.AbstractExpression
      org.exist.xquery.PathExpr
          org.exist.xquery.Function

All Implemented Interfaces:

CompiledXQuery, Expression, CompiledExpression

Direct Known Subclasses:

BasicFunction, CallFunction, CatchFunction, CollatingFunction, DescribeFunction, ExtCollection, ExtDoctype, ExtDocument, ExtFulltext, ExtRegexp, FtIndexLookup, FunAbs, FunAvg, FunBoolean, FunCeiling, FunConcat, FunCount, FunctionCall, FunCurrentDateTime, FunData, FunDoc, FunDocAvailable, FunDoctype, FunDocumentURI, FunEmpty, FunEncodeForURI, FunEscapeHTMLURI, FunExactlyOne, FunExists, FunFloor, FunId, FunImplicitTimezone, FunInsertBefore, FunIRIToURI, FunItemAt, FunLang, FunLast, FunLocalName, FunMatches, FunName, FunNamespaceURI, FunNodeName, FunNormalizeSpace, FunNormalizeUnicode, FunNot, FunNumber, FunOneOrMore, FunPosition, FunRemove, FunResolveURI, FunReverse, FunRoot, FunRound, FunRoundHalfToEven, FunString, FunStringPad, FunStrLength, FunSubSequence, FunSubstring, FunSum, FunTranslate, FunUnordered, FunUpperOrLowerCase, FunZeroOrOne, GetAttribute, GetID, InternalFunctionCall, JavaCall, LockFunction, MatchRegexp, MD5, NGramSearch, QNameIndexLookup, RangeExpression, RemoveAttribute, SetAttribute, SetCookie, SetHeader, UserDefinedFunction, UUID

public abstract class Function
extends PathExpr

Abstract base class for all built-in and user-defined functions. Built-in functions just extend this class. A new function instance will be created for each function call. Subclasses have to provide a function signature to the constructor. User-defined functions extend class UserDefinedFunction, which is again a subclass of Function. They will not be called directly, but through a FunctionCall object, which checks the type and cardinality of all arguments and takes care that the current execution context is saved properly.

Author:

wolf

Field Summary

static String

BUILTIN_FUNCTION_NS

Fields inherited from interface org.exist.xquery.Expression

DOT_TEST, EXPRESSION_ID_INVALID, IGNORE_CONTEXT, IN_PREDICATE, IN_UPDATE, IN_WHERE_CLAUSE, NEED_INDEX_INFO, NO_CONTEXT_ID, SINGLE_STEP_EXECUTION

Method Summary

void	accept(ExpressionVisitor visitor) Start traversing the expression tree using the specified ExpressionVisitor.
void	analyze(AnalyzeContextInfo contextInfo) Statically analyze the expression and its subexpressions.
static Function	createFunction(XQueryContext context, XQueryAST ast, FunctionDef def) Create a built-in function from the specified class.
void	dump(ExpressionDumper dumper) Write a diagnostic dump of the expression to the passed ExpressionDumper.
abstract Sequence	eval(Sequence contextSequence, Item contextItem) Evaluate the expression represented by this object.
Expression	getArgument(int pos) Get an argument expression by its position in the argument list.
int	getArgumentCount() Get the number of arguments passed to this function.
Sequence[]	getArguments(Sequence contextSequence, Item contextItem)
XQueryAST	getASTNode() Returns the XQueryAST node from which this expression has been constructed by the parser.
int	getCardinality() The default cardinality is Cardinality.EXACTLY_ONE.
int	getDependencies() Returns Dependency.DEFAULT_DEPENDENCIES.
QName	getName() Return the name of this function.
Expression	getParent() Returns the expression from which this function gets called.
FunctionSignature	getSignature() Get the signature of this function.
boolean	isCalledAs(String localName)
int	returnsType() The static return type of the expression.
void	setArguments(List arguments) Set the (static) arguments for this function from a list of expressions.
void	setASTNode(XQueryAST ast)
void	setParent(Expression parent) Set the parent expression of this function, i.e.
void	setPrimaryAxis(int axis)
String	toString()

Methods inherited from class org.exist.xquery.PathExpr

add, add, addPath, addPredicate, dump, getContext, getDocumentSet, getExpression, getLastExpression, getLength, getLiteralValue, getSource, isValid, replaceExpression, replaceLastExpression, reset, resetState, setContext, setSource

Methods inherited from class org.exist.xquery.AbstractExpression

eval, getContextDocSet, getContextId, getExpressionId, setContextDocSet

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.exist.xquery.CompiledXQuery

eval

Field Detail

BUILTIN_FUNCTION_NS

public static final String BUILTIN_FUNCTION_NS

See Also:

Constant Field Values

Method Detail

returnsType

public int returnsType()

Description copied from interface: Expression

The static return type of the expression. This method should return one of the type constants defined in class Type. If the return type cannot be determined statically, return Type.ITEM.

Specified by:

returnsType in interface Expression

Overrides:

returnsType in class PathExpr

getCardinality

public int getCardinality()

Description copied from class: AbstractExpression

The default cardinality is Cardinality.EXACTLY_ONE.

Specified by:

getCardinality in interface Expression

Overrides:

getCardinality in class PathExpr

createFunction

public static Function createFunction(XQueryContext context,
                                      XQueryAST ast,
                                      FunctionDef def)
                               throws XPathException

Create a built-in function from the specified class.

Returns:

the created function or null if the class could not be initialized.

Throws:

XPathException

setParent

public void setParent(Expression parent)

Set the parent expression of this function, i.e. the expression from which the function is called.

Parameters:

parent -

getParent

public Expression getParent()

Returns the expression from which this function gets called.

Overrides:

getParent in class PathExpr

setArguments

public void setArguments(List arguments)
                  throws XPathException

Set the (static) arguments for this function from a list of expressions. This will also check the type and cardinality of the passed argument expressions.

Parameters:

arguments -

Throws:

XPathException

analyze

public void analyze(AnalyzeContextInfo contextInfo)
             throws XPathException

Description copied from interface: Expression

Statically analyze the expression and its subexpressions. During the static analysis phase, the query engine can detect unknown variables and some type errors.

Specified by:

analyze in interface Expression

Overrides:

analyze in class PathExpr

Throws:

XPathException

eval

public abstract Sequence eval(Sequence contextSequence,
                              Item contextItem)
                       throws XPathException

Description copied from interface: Expression

Evaluate the expression represented by this object. Depending on the context in which this expression is executed, either the context sequence, the context item or both of them may be set. An implementing class should know how to handle this. The general contract is as follows: if the Dependency.CONTEXT_ITEM bit is set in the bit field returned by Expression.getDependencies(), the eval method will be called once for every item in the context sequence. The contextItem parameter will be set to the current item. Otherwise, the eval method will only be called once for the whole context sequence and contextItem will be null. eXist tries to process the entire context set in one, single step whenever possible. Thus, most classes only expect context to contain a list of nodes which represents the current context of the expression. The position() function in XPath is an example for an expression, which requires both, context sequence and context item to be set. The context sequence might be a node set, a sequence of atomic values or a single node or atomic value.

Specified by:

eval in interface Expression

Overrides:

eval in class PathExpr

Parameters:

contextSequence - the current context sequence.

contextItem - a single item, taken from context. This defines the item, the expression should work on.

Throws:

XPathException

getArguments

public Sequence[] getArguments(Sequence contextSequence,
                               Item contextItem)
                        throws XPathException

Throws:

XPathException

getArgument

public Expression getArgument(int pos)

Get an argument expression by its position in the argument list.

Parameters:

pos -

getArgumentCount

public int getArgumentCount()

Get the number of arguments passed to this function.

Returns:

number of arguments

setPrimaryAxis

public void setPrimaryAxis(int axis)

Specified by:

setPrimaryAxis in interface Expression

Overrides:

setPrimaryAxis in class PathExpr

getName

public QName getName()

Return the name of this function.

Returns:

name of this function

getSignature

public FunctionSignature getSignature()

Get the signature of this function.

Returns:

signature of this function

isCalledAs

public boolean isCalledAs(String localName)

getDependencies

public int getDependencies()

Description copied from class: AbstractExpression

Returns Dependency.DEFAULT_DEPENDENCIES.

Specified by:

getDependencies in interface Expression

Overrides:

getDependencies in class PathExpr

Returns:

set of bit-flags

See Also:

Expression.getDependencies()

dump

public void dump(ExpressionDumper dumper)

Description copied from interface: Expression

Write a diagnostic dump of the expression to the passed ExpressionDumper.

Specified by:

dump in interface Expression

Overrides:

dump in class PathExpr

Parameters:

dumper - the expression dumper to write to

toString

public String toString()

Overrides:

toString in class PathExpr

setASTNode

public void setASTNode(XQueryAST ast)

Specified by:

setASTNode in interface Expression

Overrides:

setASTNode in class AbstractExpression

getASTNode

public XQueryAST getASTNode()

Description copied from interface: Expression

Returns the XQueryAST node from which this expression has been constructed by the parser. This node contains location information (line number and column) important for error reports.

Specified by:

getASTNode in interface Expression

Overrides:

getASTNode in class PathExpr

Returns:

XQueryAST node

accept

public void accept(ExpressionVisitor visitor)

Description copied from interface: Expression

Start traversing the expression tree using the specified ExpressionVisitor.

Specified by:

accept in interface Expression

Overrides:

accept in class PathExpr