net.sf.saxon.expr
Class ExpressionParser

java.lang.Object
  net.sf.saxon.expr.ExpressionParser

Direct Known Subclasses:

QueryParser

public class ExpressionParser
extends Object

Parser for XPath expressions and XSLT patterns. This code was originally inspired by James Clark's xt but has been totally rewritten (several times)

Author:

Michael Kay

Nested Class Summary

static class

ExpressionParser.ForClause

Field Summary

protected StaticContext	env
protected int	numberOfRangeVariables
protected Stack	rangeVariables
protected boolean	scanOnly
protected Tokenizer	t

Constructor Summary

ExpressionParser()

Method Summary

protected String	currentTokenDisplay() Display the current token in an error message
protected void	declareRangeVariable(VariableDeclaration declaration) Declare a range variable (record its existence within the parser).
protected void	expect(int token) Expect a given token, fail if the current token is different
protected String	getLanguage() Get the current language (XPath or XQuery)
Stack	getRangeVariableStack() Get the range variable stack.
Tokenizer	getTokenizer()
protected void	grumble(String message) Report a parsing error
protected boolean	isKeyword(String s) Test whether the current token is a given keyword.
LocalNameTest	makeLocalNameTest(short nodeType, String localName) Make a LocalNameTest (*:name)
protected SourceLocator	makeLocator() Create a SourceLocator for use in an exception
int	makeNameCode(String qname, boolean useDefault) Make a NameCode, using this Element as the context for namespace resolution
NamespaceTest	makeNamespaceTest(short nodeType, String prefix) Make a NamespaceTest (name:*)
NameTest	makeNameTest(short nodeType, String qname, boolean useDefault) Make a NameTest, using the static context for namespace resolution
protected StringValue	makeStringLiteral(String currentTokenValue) Method to make a string literal from a token identified as a string literal.
protected void	nextToken() Read the next token, catching any exception thrown by the tokenizer
Expression	parse(String expression, int start, int terminator, StaticContext env) Parse a string representing an expression
protected Expression	parseConstructor() Parse a node constructor.
protected Expression	parseExpression() Parse a top-level Expression: ExprSingle ( ',' ExprSingle )*
protected Expression	parseExprSingle() Parse an ExprSingle
protected Expression	parseForExpression() Parse a FOR expression: for $x in expr (',' $y in expr)* 'return' expr
protected Expression	parseMappingExpression() Parse a mapping expression.
protected NodeTest	parseNodeTest(short nodeType) Parse a NodeTest.
Pattern	parsePattern(String pattern, StaticContext env) Parse a string representing an XSLT pattern
protected Expression	parseRelativePath() Parse a relative path (a sequence of steps).
protected SequenceType	parseSequenceType() Parse the sequence type production.
SequenceType	parseSequenceType(String input, StaticContext env) Parse a string representing a sequence type
protected Expression	parseStepExpression() Parse a step (including an optional sequence of predicates)
protected Expression	parseTypeswitchExpression() Parse a Typeswitch Expression.
protected Expression	parseValidateExpression() Parse a Validate Expression.
protected void	setLocation(Expression exp) Set location information on an expression.
protected void	setLocation(Expression exp, int line) Set location information on an expression.
void	setRangeVariableStack(Stack stack) Set the range variable stack.
void	setScanOnly(boolean scanOnly)
protected void	undeclareRangeVariable() Note when the most recently declared range variable has gone out of scope
protected void	warning(String message) Output a warning message

Methods inherited from class java.lang.Object

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

Field Detail

t

protected Tokenizer t

env

protected StaticContext env

numberOfRangeVariables

protected int numberOfRangeVariables

rangeVariables

protected Stack rangeVariables

scanOnly

protected boolean scanOnly

Constructor Detail

ExpressionParser

public ExpressionParser()

Method Detail

getTokenizer

public Tokenizer getTokenizer()

nextToken

protected void nextToken()
                  throws XPathException

Read the next token, catching any exception thrown by the tokenizer

Throws:

XPathException

expect

protected void expect(int token)
               throws XPathException

Expect a given token, fail if the current token is different

Parameters:

token - the expected token

Throws:

XPathException - if the current token is not the expected token

grumble

protected void grumble(String message)
                throws XPathException

Report a parsing error

Parameters:

message - the error message

Throws:

XPathException - always thrown: an exception containing the supplied message

warning

protected void warning(String message)
                throws XPathException

Output a warning message

Throws:

XPathException

getLanguage

protected String getLanguage()

Get the current language (XPath or XQuery)

currentTokenDisplay

protected String currentTokenDisplay()

Display the current token in an error message

Returns:

the display representation of the token

parse

public Expression parse(String expression,
                        int start,
                        int terminator,
                        StaticContext env)
                 throws XPathException

Parse a string representing an expression

Parameters:

expression - the expression expressed as a String

env - the static context for the expression

Returns:

an Expression object representing the result of parsing

Throws:

XPathException - if the expression contains a syntax error

parsePattern

public Pattern parsePattern(String pattern,
                            StaticContext env)
                     throws XPathException

Parse a string representing an XSLT pattern

Parameters:

pattern - the pattern expressed as a String

env - the static context for the pattern

Returns:

a Pattern object representing the result of parsing

Throws:

XPathException - if the pattern contains a syntax error

parseSequenceType

public SequenceType parseSequenceType(String input,
                                      StaticContext env)
                               throws XPathException

Parse a string representing a sequence type

Parameters:

input - the string, which should conform to the XPath SequenceType production

env - the static context

Returns:

a SequenceType object representing the type

Throws:

XPathException - if any error is encountered

parseExpression

protected Expression parseExpression()
                              throws XPathException

Parse a top-level Expression: ExprSingle ( ',' ExprSingle )*

Returns:

the Expression object that results from parsing

Throws:

XPathException - if the expression contains a syntax error

parseExprSingle

protected Expression parseExprSingle()
                              throws XPathException

Parse an ExprSingle

Returns:

the resulting subexpression

Throws:

XPathException - if any error is encountered

parseTypeswitchExpression

protected Expression parseTypeswitchExpression()
                                        throws XPathException

Parse a Typeswitch Expression. This construct is XQuery-only, so the XPath version of this method throws an error unconditionally

Throws:

XPathException

parseValidateExpression

protected Expression parseValidateExpression()
                                      throws XPathException

Parse a Validate Expression. This construct is XQuery-only, so the XPath version of this method throws an error unconditionally

Throws:

XPathException

parseForExpression

protected Expression parseForExpression()
                                 throws XPathException

Parse a FOR expression: for $x in expr (',' $y in expr)* 'return' expr

Returns:

the resulting subexpression

Throws:

XPathException - if any error is encountered

parseMappingExpression

protected Expression parseMappingExpression()
                                     throws XPathException

Parse a mapping expression. This is a common routine that handles XPath for expressions and quantified expressions.

Syntax:
(for|some|every) $x in expr (',' $y in expr)* (return|satisfies) expr

On entry, the current token indicates whether a for, some, or every expression is expected.

Returns:

the resulting subexpression

Throws:

XPathException - if any error is encountered

parseSequenceType

protected SequenceType parseSequenceType()
                                  throws XPathException

Parse the sequence type production. Provisionally, we use the syntax (QName | node-kind "()") ( "*" | "+" | "?" )? We also allow "element of type QName" and "attribute of type QName" The QName must be the name of a built-in schema-defined data type.

Returns:

the resulting subexpression

Throws:

XPathException - if any error is encountered

parseRelativePath

protected Expression parseRelativePath()
                                throws XPathException

Parse a relative path (a sequence of steps). Called when the current token immediately follows a separator (/ or //), or an implicit separator (XYZ is equivalent to ./XYZ)

Returns:

the resulting subexpression

Throws:

XPathException - if any error is encountered

parseStepExpression

protected Expression parseStepExpression()
                                  throws XPathException

Parse a step (including an optional sequence of predicates)

Returns:

the resulting subexpression

Throws:

XPathException - if any error is encountered

makeStringLiteral

protected StringValue makeStringLiteral(String currentTokenValue)
                                 throws XPathException

Method to make a string literal from a token identified as a string literal. This is trivial in XPath, but in XQuery the method is overridden to identify pseudo-XML character and entity references

Parameters:

currentTokenValue -

Returns:

The string value of the string literal

Throws:

XPathException

parseConstructor

protected Expression parseConstructor()
                               throws XPathException

Parse a node constructor. This is allowed only in XQuery, so the method throws an error for XPath.

Throws:

XPathException

parseNodeTest

protected NodeTest parseNodeTest(short nodeType)
                          throws XPathException

Parse a NodeTest. One of QName, prefix:*, *:suffix, *, text(), node(), comment(), or processing-instruction(literal?), or element(~,~), attribute(~,~), etc.

Parameters:

nodeType - the node type being sought if one is specified

Returns:

the resulting NodeTest object

Throws:

XPathException - if any error is encountered

declareRangeVariable

protected void declareRangeVariable(VariableDeclaration declaration)
                             throws XPathException

Declare a range variable (record its existence within the parser). A range variable is a variable declared within an expression, as distinct from a variable declared in the context.

Parameters:

declaration - the VariableDeclaration to be added to the stack

Throws:

XPathException - if any error is encountered

undeclareRangeVariable

protected void undeclareRangeVariable()

Note when the most recently declared range variable has gone out of scope

getRangeVariableStack

public Stack getRangeVariableStack()

Get the range variable stack. Used when parsing a nested subexpression inside an attribute constructor

setRangeVariableStack

public void setRangeVariableStack(Stack stack)

Set the range variable stack. Used when parsing a nested subexpression inside an attribute constructor.

makeNameCode

public final int makeNameCode(String qname,
                              boolean useDefault)
                       throws XPathException

Make a NameCode, using this Element as the context for namespace resolution

Parameters:

qname - The name as written, in the form "[prefix:]localname"

useDefault - Defines the action when there is no prefix. If true, use the default namespace URI for element names. If false, use no namespace URI (as for attribute names).

Returns:

the namecode, which can be used to identify this name in the name pool

Throws:

XPathException - if the name is invalid, or the prefix undeclared

makeNameTest

public NameTest makeNameTest(short nodeType,
                             String qname,
                             boolean useDefault)
                      throws XPathException

Make a NameTest, using the static context for namespace resolution

Parameters:

nodeType - the type of node required (identified by a constant in class Type)

qname - the lexical QName of the required node

useDefault - true if the default namespace should be used when the QName is unprefixed

Returns:

a NameTest, representing a pattern that tests for a node of a given node kind and a given name

Throws:

XPathException - if the QName is invalid

makeNamespaceTest

public NamespaceTest makeNamespaceTest(short nodeType,
                                       String prefix)
                                throws XPathException

Make a NamespaceTest (name:*)

Parameters:

nodeType - integer code identifying the type of node required

prefix - the namespace prefix

Returns:

the NamespaceTest, a pattern that matches all nodes in this namespace

Throws:

XPathException - if the namespace prefix is not declared

makeLocalNameTest

public LocalNameTest makeLocalNameTest(short nodeType,
                                       String localName)
                                throws XPathException

Make a LocalNameTest (*:name)

Parameters:

nodeType - the kind of node to be matched

localName - the requred local name

Returns:

a LocalNameTest, a pattern which matches all nodes of a given local name, regardless of namespace

Throws:

XPathException - if the local name is invalid

setLocation

protected void setLocation(Expression exp)

Set location information on an expression. At present this consists of a simple line number. Needed mainly for XQuery.

setLocation

protected void setLocation(Expression exp,
                           int line)

Set location information on an expression. At present this consists of a simple line number. Needed mainly for XQuery. This version of the method supplies an explicit line number.

makeLocator

protected SourceLocator makeLocator()

Create a SourceLocator for use in an exception

isKeyword

protected boolean isKeyword(String s)

Test whether the current token is a given keyword.

Parameters:

s - The string to be compared with the current token

Returns:

true if they are the same

setScanOnly

public void setScanOnly(boolean scanOnly)