com.beasys.commerce.util
Class ExpressionHelper

java.lang.Object
  |
  +--com.beasys.commerce.util.ExpressionHelper

public class ExpressionHelper

extends java.lang.Object

Helper class to handle dealing with Expression, Criteria, and Logical objects.

See Also:

Expression, Criteria, Logical

Inner Class Summary

static interface

ExpressionHelper.ParseException Exception to report an error while parsing a query expression.

Constructor Summary

ExpressionHelper()

Method Summary

static ExpressionHelper.ParseException	convertException(java.lang.Exception excep) Convert a generic exception into a ParseException.
static java.lang.String	fromStringLiteral(java.lang.String in) Convert a String literal (which may contain quoted characters) into a corresponding String value.
static int	getOrdinalValue(char ch) Get the ordinal (Unicode) value of a character.
static boolean	isHexString(java.lang.String str) Determine is a string contains only ASCII hexidecimal characters ([0-9a-fA-F]).
static Logical	join(Expression expr1, Expression expr2) Join together two expression via an AND expression.
static Expression	normalize(Expression expr) Normalize an Expression.
static Expression	parse(java.lang.String queryStr) Convert a query expression string into an Expression object.
static void	printTree(int depth, java.io.PrintWriter out, Expression expr) For debug purposes, print the given expression as a tree at the given depth.
static void	printTree(java.io.PrintWriter out, Expression expr) For debug purposes, print the given expression as a tree.
static java.lang.String	toString(Criteria c) Return a string representation of the given criteria.
static java.lang.String	toString(Expression expr) Get a string representation of the given expression.
static java.lang.String	toString(Logical l) Return a string representation of the given Logical.
static java.lang.String	toStringLiteral(java.lang.String in) Get an ASCII String literal from a Java string.
static java.lang.String	toTree(Expression expr) For debug purposes, return a tree representation of the given expression.

Methods inherited from class java.lang.Object

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

Constructor Detail

ExpressionHelper

public ExpressionHelper()

Method Detail

parse

public static Expression parse(java.lang.String queryStr)
                        throws ExpressionHelper.ParseException,
                               java.lang.IllegalArgumentException

Convert a query expression string into an Expression object.

The string should follow the query syntax specified in the Personalization Server documentation. The expression syntax is tree-based, with each leaf in the tree beinging of the form "property comparator value" (e.g. "identifier == '1234'").

Property (LHS)

This specifies the object property to match against. To specify a property name which contains non-identifier characters (e.g. whitespace, double quotes, dashes), you can use the "toProperty('property name')" form in the left-hand-side. To specify scopenames as part of the property name, either use the "scope.name" form or the "toProperty('scope', 'property')" form in the left-hand-side.

Comparators

The valid comparision operators are = (or ==), !=, <, >, <=, >=, "like", and "contains". The "like" operator expects the pattern (which is the value of the leaf) to use * (match all) and ? (match any); "like" also is only expected to work against String values, although it might work with other datatypes depending upon the search implementation. The "contains" operator is only expected to work against multi-valued properties, although it might work with other datatypes depending upon the search implementation.

Value (RHS)

• String literal values are enclosed in single quotes (back-slash is the quoting character, unicode characters not supported). Additionally, unicode (e.g. "\u6565"), octal (e.g. "\7", "\65", "\377"), and standard Java escape sequences (e.g. "\n", "\r", "\b") are allowed in the string literals.
• Boolean literal are either the "true" or "false" keyword (without quotes).
• Number literals are Java form (scientific notation is supported).
• Time literals are presented in "toDate(['formatStr'], 'dateStr')" format. formatStr must be a valid SimpleDateFormat format string; if omitted, 'MM/dd/yyyy HH:mm:ss z' is used. Also, the "now" keyword specifies the current time/date.
• Collections cannot be represented in the expression syntax.

Each branch in the tree is comprised of 1 or more leafs or branches separated by either "&&" (boolean AND) or "||" (boolean OR). They can be enclosed in parenthesis for clearity and ordering (AND has precendance over OR). Additionally, "!" marks a branch as using negative logical (boolean NOT). The "!" operator can only be used preceding an open parenthesis.

Examples of valid expression strings:

• identifier == '00099abv48932ds'
• ((UserAge <= 35 && colors contains 'red') || (UserAge > 35 && !(colors contains 'black')) && mimeType == 'text/html'
• toProperty('MyApp', 'Launch Date') < now && !(MyApp.expireDate > toDate('HH:mm:ss MM-dd-yyyy', '12:12:12 12/12/2002'))

Parameters:

queryStr - the query expression string

Returns:

an Expression object representing (null if queryStr is a null expression).

Throws:

ExpressionHelper.ParseException - thrown on a an invalid expression query or a parser error.

java.lang.IllegalArgumentException - thrown on a general error.

See Also:

convertException(java.lang.Exception), normalize(com.beasys.commerce.foundation.expression.Expression)

join

public static Logical join(Expression expr1,
                           Expression expr2)

Join together two expression via an AND expression.

Parameters:

expr1 - the first expression.

expr2 - the second expression.

Returns:

a Logical of the two expressions.

normalize

public static Expression normalize(Expression expr)

Normalize an Expression.

This will remove:

• Non-root Logicals which contain only one Expression
• Logicals which contain only one Criteria.

Parameters:

expr - the incoming expression.

Returns:

the normalized expression, null if normalized to nothing.

toString

public static java.lang.String toString(Expression expr)

Get a string representation of the given expression.

Pretty much, a string generated from this method can be parse()'ed into the equivalent (not neccessarily identical) expression tree.

Parameters:

expr - the expression.

Returns:

the query syntax representation of the expression.

toString

public static java.lang.String toString(Criteria c)

Return a string representation of the given criteria.

toString

public static java.lang.String toString(Logical l)

Return a string representation of the given Logical.

toTree

public static java.lang.String toTree(Expression expr)

For debug purposes, return a tree representation of the given expression.

printTree

public static void printTree(java.io.PrintWriter out,
                             Expression expr)

For debug purposes, print the given expression as a tree.

Parameters:

out - the output stream to print on.

expr - the expression.

printTree

public static void printTree(int depth,
                             java.io.PrintWriter out,
                             Expression expr)

For debug purposes, print the given expression as a tree at the given depth.

Parameters:

depth - the depth of this expression in the tree.

out - the output stream to print on.

expr - the expression.

fromStringLiteral

public static java.lang.String fromStringLiteral(java.lang.String in)

Convert a String literal (which may contain quoted characters) into a corresponding String value.

This supports the standard Java Language Specification escape sequences.

Parameters:

in - the input string literal.

Returns:

the string value.

isHexString

public static boolean isHexString(java.lang.String str)

Determine is a string contains only ASCII hexidecimal characters ([0-9a-fA-F]).

toStringLiteral

public static java.lang.String toStringLiteral(java.lang.String in)

Get an ASCII String literal from a Java string.

This will quote some special characters with back-slashes.

The output of this can be sent through fromStringLiteral(java.lang.String) to result in the original String.

getOrdinalValue

public static int getOrdinalValue(char ch)

Get the ordinal (Unicode) value of a character.

convertException

public static ExpressionHelper.ParseException convertException(java.lang.Exception excep)

Convert a generic exception into a ParseException.