org.xlattice.corexml.expr
Class ExprParser

java.lang.Object
  org.xlattice.corexml.expr.ExprParser

public class ExprParser
extends java.lang.Object

XPath 1.0 expression parser. This class is best understood by reading it with the W3C XPath 1.0 specification in hand.

The parse() method accepts an expression in String form, tokenizes it using its lexer, and returns an unevaluated expression tree.

The eval() method accepts an XPath expression tree and returns a result. The evaluation is done given the current context and context node. XPath return types do not map particularly well into Java types.

This implementation is incomplete.

• all operators and symbols are recognized
• primary expressions are parsed
• most XPath library functions are not implemented
• location paths are dealt with only along the child axis and from the document root

Author:

Jim Dixon

Field Summary

protected org.xlattice.Context	ctx the context, hashed access to global variables
protected Node	node the node expressions are evaluated in relation to
static NodeTest	NTEST_COMMENT
static NodeTest	NTEST_ELEMENT
static NodeTest	NTEST_NODE
static NodeTest	NTEST_PI
static NodeTest	NTEST_STAR
static NodeTest	NTEST_TEXT
static NodeType	NTYPE_COMMENT
static NodeType	NTYPE_ELEMENT
static NodeType	NTYPE_NODE
static NodeType	NTYPE_PI
static NodeType	NTYPE_TEXT
static Operator	OP_DSLASH
static Operator	OP_SLASH
static Operator	OP_STAR
static Symbol	SYM_COLON
static Symbol	SYM_DCOLON
static Symbol	SYM_DDOT
static Symbol	SYM_DOT
static Symbol	SYM_LBRACKET
static Symbol	SYM_LPAREN
static Symbol	SYM_RBRACKET
static Symbol	SYM_RPAREN
static Symbol	SYM_STAR

Constructor Summary

ExprParser(Node n, org.xlattice.Context c)
Create an expression parser.

Method Summary

static boolean	booleanFunc(java.lang.Object o)
void	cantCast(Expr e)
Bool	castToBool(Expr e)
Literal	castToLiteral(Expr e)
Numeric	castToNumeric(Expr e)
(package private) NodeTest	collectNodeTest() Expect the next tokens from the lexer to represent a NodeTest.
(package private) Step	collectPredicates(Step step) Given a step, collect any predicates following it.
(package private) Step	collectStep(AxisName aName, boolean single) Having encountered an axis name, collect the step.
(package private) Step	collectStep(NCName ncName, boolean single) Verify NCName followed by :*, then collect the step, defaulting it to one along the CHILD axis.
(package private) Step	collectStep(NodeType nodeType, boolean single) Having encountered a nodeType, collect the step, defaulting it to one along the CHILD axis.
(package private) Step	collectStep(QName qName, boolean single) Having encountered a QName, collect the step, defaulting it to one along the CHILD axis.
(package private) Step	collectStep(Symbol sym, boolean single) Having encountered a symbol, collect the step.
(package private) LocationPath	collectSteps(LocationPath lp, boolean single, boolean required) Collect a series of steps and append them to the location path, which is returned.
static java.lang.String	concat(java.lang.String[] args) This interface deviates from the specs, because Java 1.4 doesn't support variable length argument lists.
static Numeric	count(NodeSet nodes) XPath NodeSet function 1, count.
Expr	eval(Expr e)
Expr	eval(java.lang.String str)
(package private) Bool	evalBoolBinary(BinaryExpr e)
(package private) Literal	evalLiteralBinary(BinaryExpr e)
(package private) NodeSet	evalLocationPath(LocationPath lp)
(package private) NodeSet	evalNodeSetBinary(BinaryExpr e)
(package private) Numeric	evalNumericBinary(BinaryExpr e)
(package private) void	expect(Token t)
Node	getNode()
Numeric	id()
Numeric	last()
java.lang.String	localName()
static java.lang.String	localName(NodeSet nodes)
java.lang.String	name()
static java.lang.String	name(NodeSet nodes)
java.lang.String	namespaceUri()
static java.lang.String	namespaceUri(NodeSet nodes)
static java.lang.Double	number()
static java.lang.Double	number(java.lang.Object o) XPath numeric function 1, number()
Expr	parse(java.lang.String str) Parse a String holding an XPath expression.
(package private) LocationPath	parseAbsLocationPath(Operator op) Parse an absolute location path, having encountered an Operator token.
(package private) BinaryExpr	parseAdditiveExpr(Operator op, Expr left)
(package private) BinaryExpr	parseAndExpr(Operator op, Expr left)
(package private) BinaryExpr	parseEqualityExpr(Operator op, Expr left)
(package private) BinaryExpr	parseMultiplicativeExpr(Operator op, Expr left)
(package private) BinaryExpr	parseOrExpr(Operator op, Expr left)
(package private) BinaryExpr	parseRelationalExpr(Operator op, Expr left)
(package private) LocationPath	parseRelLocationPath(Token t) Parse an absolute location path, having encountered the current token.
(package private) LocationPath	parseStep(Token t, Expr soFar) Parse a step beginning with Token, using the expression collected so far to build a location path.
(package private) UnaryExpr	parseUnaryExpr(Operator op) Parse a unary expression with a leading minus.
(package private) BinaryExpr	parseUnionExpr(Operator op, Expr left) Called after seeing a '|' (BAR)
Numeric	position()
void	setNode(Node newContextNode) Change the context node, the node that expressions are evaluated in relation to.
java.lang.String	string() Convert the context node.
static java.lang.String	string(Node node) XPath String function 1, string(node).
static java.lang.String	string(java.lang.Object e) Convert objects to Java Strings in accordance with the spec.
(package private) Node	takeStep(Node ctxNode, NodeSet collected, java.util.ArrayList steps)

Methods inherited from class java.lang.Object

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

Field Detail

node

protected Node node

the node expressions are evaluated in relation to

ctx

protected final org.xlattice.Context ctx

the context, hashed access to global variables

OP_SLASH

public static final Operator OP_SLASH

OP_DSLASH

public static final Operator OP_DSLASH

OP_STAR

public static final Operator OP_STAR

SYM_COLON

public static final Symbol SYM_COLON

SYM_DCOLON

public static final Symbol SYM_DCOLON

SYM_DOT

public static final Symbol SYM_DOT

SYM_DDOT

public static final Symbol SYM_DDOT

SYM_LBRACKET

public static final Symbol SYM_LBRACKET

SYM_LPAREN

public static final Symbol SYM_LPAREN

SYM_RBRACKET

public static final Symbol SYM_RBRACKET

SYM_RPAREN

public static final Symbol SYM_RPAREN

SYM_STAR

public static final Symbol SYM_STAR

NTYPE_COMMENT

public static final NodeType NTYPE_COMMENT

NTEST_COMMENT

public static final NodeTest NTEST_COMMENT

NTYPE_ELEMENT

public static final NodeType NTYPE_ELEMENT

NTEST_ELEMENT

public static final NodeTest NTEST_ELEMENT

NTYPE_NODE

public static final NodeType NTYPE_NODE

NTEST_NODE

public static final NodeTest NTEST_NODE

NTYPE_PI

public static final NodeType NTYPE_PI

NTEST_PI

public static final NodeTest NTEST_PI

NTYPE_TEXT

public static final NodeType NTYPE_TEXT

NTEST_TEXT

public static final NodeTest NTEST_TEXT

NTEST_STAR

public static final NodeTest NTEST_STAR

Constructor Detail

ExprParser

public ExprParser(Node n,
                  org.xlattice.Context c)

Create an expression parser.

Parameters:

n - current node

c - current context

Method Detail

getNode

public Node getNode()

Returns:

the context node

setNode

public void setNode(Node newContextNode)

Change the context node, the node that expressions are evaluated in relation to.

expect

void expect(Token t)
      throws CoreXmlException

Throws:

CoreXmlException - if t not next Token from lexer

parse

public Expr parse(java.lang.String str)
           throws CoreXmlException

Parse a String holding an XPath expression. If the String is null or empty, return null. Otherwise, return an unevaluated expression tree.

Returns:

a parse tree

Throws:

CoreXmlException

parseAbsLocationPath

LocationPath parseAbsLocationPath(Operator op)
                            throws CoreXmlException

Parse an absolute location path, having encountered an Operator token.

Returns:

a LocationPath subexpression tree

Throws:

CoreXmlException

parseRelLocationPath

LocationPath parseRelLocationPath(Token t)
                            throws CoreXmlException

Parse an absolute location path, having encountered the current token.

Returns:

a LocationPath subexpression tree

Throws:

CoreXmlException

collectSteps

LocationPath collectSteps(LocationPath lp,
                          boolean single,
                          boolean required)
                    throws CoreXmlException

Collect a series of steps and append them to the location path, which is returned.

Parameters:

lp - location path input

single - collect only one step

required - whether a step MUST be found

Returns:

location path with steps appended

Throws:

CoreXmlException

collectStep

Step collectStep(AxisName aName,
                 boolean single)
           throws CoreXmlException

Having encountered an axis name, collect the step.

Throws:

CoreXmlException

collectStep

Step collectStep(Symbol sym,
                 boolean single)
           throws CoreXmlException

Having encountered a symbol, collect the step.

Throws:

CoreXmlException

collectStep

Step collectStep(NodeType nodeType,
                 boolean single)
           throws CoreXmlException

Having encountered a nodeType, collect the step, defaulting it to one along the CHILD axis.

Throws:

CoreXmlException

collectStep

Step collectStep(NCName ncName,
                 boolean single)
           throws CoreXmlException

Verify NCName followed by :*, then collect the step, defaulting it to one along the CHILD axis.

Throws:

CoreXmlException

collectStep

Step collectStep(QName qName,
                 boolean single)
           throws CoreXmlException

Having encountered a QName, collect the step, defaulting it to one along the CHILD axis.

Throws:

CoreXmlException

collectNodeTest

NodeTest collectNodeTest()
                   throws CoreXmlException

Expect the next tokens from the lexer to represent a NodeTest.

Returns:

the NodeTest constructed from the stream of Tokens

Throws:

CoreXmlException

collectPredicates

Step collectPredicates(Step step)
                 throws CoreXmlException

Given a step, collect any predicates following it.

Throws:

CoreXmlException

parseStep

LocationPath parseStep(Token t,
                       Expr soFar)
                 throws CoreXmlException

Parse a step beginning with Token, using the expression collected so far to build a location path.

Parameters:

t - curent token

soFar - expression seen so far, must be a LocationPath

Throws:

CoreXmlException

parseUnaryExpr

UnaryExpr parseUnaryExpr(Operator op)
                   throws CoreXmlException

Parse a unary expression with a leading minus.

Throws:

CoreXmlException

parseUnionExpr

BinaryExpr parseUnionExpr(Operator op,
                          Expr left)
                    throws CoreXmlException

Called after seeing a '|' (BAR)

Throws:

CoreXmlException

parseMultiplicativeExpr

BinaryExpr parseMultiplicativeExpr(Operator op,
                                   Expr left)
                             throws CoreXmlException

Throws:

CoreXmlException

parseAdditiveExpr

BinaryExpr parseAdditiveExpr(Operator op,
                             Expr left)
                       throws CoreXmlException

Throws:

CoreXmlException

parseRelationalExpr

BinaryExpr parseRelationalExpr(Operator op,
                               Expr left)
                         throws CoreXmlException

Throws:

CoreXmlException

parseEqualityExpr

BinaryExpr parseEqualityExpr(Operator op,
                             Expr left)
                       throws CoreXmlException

Throws:

CoreXmlException

parseAndExpr

BinaryExpr parseAndExpr(Operator op,
                        Expr left)
                  throws CoreXmlException

Throws:

CoreXmlException

parseOrExpr

BinaryExpr parseOrExpr(Operator op,
                       Expr left)
                 throws CoreXmlException

Throws:

CoreXmlException

eval

public Expr eval(java.lang.String str)
          throws CoreXmlException

Throws:

CoreXmlException

eval

public Expr eval(Expr e)
          throws CoreXmlException

Throws:

CoreXmlException

evalLocationPath

NodeSet evalLocationPath(LocationPath lp)
                   throws CoreXmlException

Throws:

CoreXmlException

takeStep

Node takeStep(Node ctxNode,
              NodeSet collected,
              java.util.ArrayList steps)
        throws CoreXmlException

Throws:

CoreXmlException

evalBoolBinary

Bool evalBoolBinary(BinaryExpr e)
              throws CoreXmlException

Throws:

CoreXmlException

evalLiteralBinary

Literal evalLiteralBinary(BinaryExpr e)
                    throws CoreXmlException

Throws:

CoreXmlException

evalNodeSetBinary

NodeSet evalNodeSetBinary(BinaryExpr e)
                    throws CoreXmlException

Throws:

CoreXmlException

evalNumericBinary

Numeric evalNumericBinary(BinaryExpr e)
                    throws CoreXmlException

Throws:

CoreXmlException

castToBool

public Bool castToBool(Expr e)
                throws CoreXmlException

Throws:

CoreXmlException

castToNumeric

public Numeric castToNumeric(Expr e)
                      throws CoreXmlException

Throws:

CoreXmlException

castToLiteral

public Literal castToLiteral(Expr e)
                      throws CoreXmlException

Throws:

CoreXmlException

cantCast

public void cantCast(Expr e)
              throws CoreXmlException

Throws:

CoreXmlException

count

public static Numeric count(NodeSet nodes)

XPath NodeSet function 1, count.

Returns:

the number of nodes in the NodeSet

id

public Numeric id()

last

public Numeric last()

name

public java.lang.String name()

name

public static java.lang.String name(NodeSet nodes)

localName

public java.lang.String localName()

localName

public static java.lang.String localName(NodeSet nodes)

namespaceUri

public java.lang.String namespaceUri()

namespaceUri

public static java.lang.String namespaceUri(NodeSet nodes)

position

public Numeric position()

string

public static java.lang.String string(Node node)

XPath String function 1, string(node).

string

public java.lang.String string()

Convert the context node. XXX Implement this by passing a NodeSet containing only the context node to the next function. XXX THE NODE BEING PASSED HERE IS NOT NECESSARILY THE CURRENT CONTEXT NODE

string

public static java.lang.String string(java.lang.Object e)

Convert objects to Java Strings in accordance with the spec. XXX This implementation is incomplete.

concat

public static java.lang.String concat(java.lang.String[] args)

This interface deviates from the specs, because Java 1.4 doesn't support variable length argument lists.

Returns:

the concatenation of its arguments

booleanFunc

public static boolean booleanFunc(java.lang.Object o)

number

public static java.lang.Double number(java.lang.Object o)

XPath numeric function 1, number()

number

public static java.lang.Double number()