org.ceryle.wiki.plugin.query
Class Expression

java.lang.Object
  org.ceryle.wiki.plugin.query.Expression

All Implemented Interfaces:

Operand

Direct Known Subclasses:

Assertion

public class Expression
extends Object
implements Operand

Expressions can be nested, combined with Operators and contain Terms. An expression when evaluated against a candidate page, returns true if the candidate page and all of its nested parts are acceptable.

Author:

John Volkar (john.volkar at gmail.com)

Nested Class Summary

Nested classes/interfaces inherited from interface org.ceryle.wiki.plugin.query.Operand

Operand.NullOperand

Field Summary

static Expression	EMPTY An Empty expression accepts everything.
protected Operand	m_left
protected Operator	m_operator
protected static ExpressionParser	m_parser This parser instance is used to do the string handling, it checks the string and builds up a list of logical elements that Expression attempts to disambiguate.
protected Operand	m_right

Fields inherited from interface org.ceryle.wiki.plugin.query.Operand

NULL

Constructor Summary

Expression(List list)
Constructor taking a List of Terms, Operators and sub-Expressions that make up this expression.

Expression(Operand left, Operator operator, Operand right)
Constructor where the Operator and two Operands of the Expression are explicit and already known.

Method Summary

boolean	accepts(String pageName, ReferenceInfoProvider refInfoProvider) Typically this method is only called by the QueryItem itsself to ask if the top-level expression would accept the pageName as being part of the result set.
boolean	evaluateOperand(Modifier modifier, ReferenceInfoProvider refInfoProvider, String pageName) Evaluates the operand, returns the truth value.
Operand	getLeftOperand()
Operator	getOperator()
Operand	getRightOperand()
static Expression	parse(String queryString) Main parsing logic to turn a String into an Expression.
String	toString() Returns formal form of this expression.

Methods inherited from class java.lang.Object

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

Field Detail

EMPTY

public static final Expression EMPTY

An Empty expression accepts everything.

m_parser

protected static ExpressionParser m_parser

This parser instance is used to do the string handling, it checks the string and builds up a list of logical elements that Expression attempts to disambiguate.

m_left

protected Operand m_left

m_operator

protected Operator m_operator

m_right

protected Operand m_right

Constructor Detail

Expression

public Expression(Operand left,
                  Operator operator,
                  Operand right)

Constructor where the Operator and two Operands of the Expression are explicit and already known.

Parameters:

left - the left side ("subject") of the expression

operator - the operator ("verb") of the expression

right - the right side ("object") of the expression

Expression

public Expression(List list)
           throws QueryException

Constructor taking a List of Terms, Operators and sub-Expressions that make up this expression. Formalizes them into a proper series of nesting expressions, result is one top-level expression and a structured tree inside of it.

Parameters:

list -

Throws:

QueryException

Method Detail

parse

public static Expression parse(String queryString)
                        throws QueryException

Main parsing logic to turn a String into an Expression. This occurs in ExpressionParser. This might be better done via a parser generator.

Parameters:

queryString -

Returns:

the generated Expression

Throws:

QueryException

getLeftOperand

public Operand getLeftOperand()

getOperator

public Operator getOperator()

getRightOperand

public Operand getRightOperand()

toString

public String toString()

Returns formal form of this expression.

Overrides:

toString in class Object

accepts

public boolean accepts(String pageName,
                       ReferenceInfoProvider refInfoProvider)
                throws QueryException

Typically this method is only called by the QueryItem itsself to ask if the top-level expression would accept the pageName as being part of the result set.

Parameters:

pageName -

refInfoProvider -

Returns:

true if pageName should be in the result set.

Throws:

QueryException

evaluateOperand

public boolean evaluateOperand(Modifier modifier,
                               ReferenceInfoProvider refInfoProvider,
                               String pageName)
                        throws QueryException

Description copied from interface: Operand

Evaluates the operand, returns the truth value.

Specified by:

evaluateOperand in interface Operand

Throws:

QueryException

See Also:

Operand