org.ow2.bonita.expression.BooleanExpression Maven / Gradle / Ivy
/**
* Copyright (C) 2009 Bull S. A. S.
* Bull, Rue Jean Jaures, B.P.68, 78340, Les Clayes-sous-Bois
* This library is free software; you can redistribute it and/or modify it under the terms
* of the GNU Lesser General Public License as published by the Free Software Foundation
* version 2.1 of the License.
* This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
* without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
* See the GNU Lesser General Public License for more details.
* You should have received a copy of the GNU Lesser General Public License along with this
* program; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth
* Floor, Boston, MA 02110-1301, USA.
**/
package org.ow2.bonita.expression;
import java.util.ArrayList;
import java.util.List;
import java.util.Vector;
import org.ow2.bonita.util.Misc;
/**
*
* @author Matthieu Chaffotte
*
*/
public class BooleanExpression {
private static final String JAVA_FIELD_PATTERN = "^[a-z][a-zA-Z0-9]*$";
private List tokens;
/**
* Create a new boolean expression.
* @param expression the expression
* @throws InvalidExpressionException if the expression is not valid
*/
public BooleanExpression(final String expression)
throws InvalidExpressionException {
Misc.checkArgsNotNull(expression);
tokens = new Vector();
checkExpression(formatExpression(expression));
}
/**
* Checks whether the expression given in parameter is a boolean expression.
* @param expression the expression to check
* @throws InvalidExpressionException if the expression is not valid
*/
private void checkExpression(String expression)
throws InvalidExpressionException {
expression = expression.trim();
if (expression.length() == 0) {
throw new InvalidExpressionException(expression,
"The expression cannot be an empty String");
}
if (expression.startsWith(KeyWord.LEFT_PARENTHESIS.value())
&& isABloc(expression)) {
tokens.add(KeyWord.LEFT_PARENTHESIS.value());
checkExpression(expression.substring(1, expression.length() - 1));
tokens.add(KeyWord.RIGHT_PARENTHESIS.value());
} else {
if (isField(expression)) {
if (!isConformField(expression)) {
throw new InvalidExpressionException(expression,
"The field is not conform to expression " + JAVA_FIELD_PATTERN);
} else {
tokens.add(expression);
}
} else {
String not = Character.toString(expression.charAt(0));
if (KeyWord.NOT.value().equals(not)) {
tokens.add(KeyWord.NOT.value());
checkExpression(expression.substring(1));
} else {
List expressions =
getExpressionsFromBinaryOperation(expression);
String operator = expressions.get(0);
String left = expressions.get(1).trim();
String right = expressions.get(2).trim();
if (left.length() == 0) {
throw new InvalidExpressionException(expression,
"The left expression is missing");
}
if (operator.length() == 0) {
throw new InvalidExpressionException(expression,
"An operator is missing");
}
if (right.length() == 0) {
throw new InvalidExpressionException(expression,
"The right expression is missing");
}
if (operator.equals(KeyWord.AND.value())
|| operator.equals(KeyWord.OR.value())
|| operator.equals(KeyWord.XOR.value())) {
checkExpression(left);
tokens.add(operator);
checkExpression(right);
} else {
throw new InvalidExpressionException(expression,
"Unknown operator : \"" + operator + "\"");
}
}
}
}
}
/**
* Checks whether the expression is a bloc.
* A bloc is a well-formed expression in parenthesis.
* (the number of left parentheses equals the number of right parentheses)
* @param expression the expression to check
* @return true if it is a bloc; false otherwise
* @throws InvalidExpressionException if the expression is invalid
*/
private static boolean isABloc(final String expression)
throws InvalidExpressionException {
boolean bloc = false;
if(expression.startsWith(KeyWord.LEFT_PARENTHESIS.value())) {
int index = 1;
int count = 1;
char current;
while (index < expression.length() && count > 0) {
current = expression.charAt(index);
if (KeyWord.LEFT_PARENTHESIS.value().equals(String.valueOf(current))) {
count++;
} else if (
KeyWord.RIGHT_PARENTHESIS.value().equals(String.valueOf(current))) {
count--;
}
index++;
}
if (count > 0) {
throw new InvalidExpressionException(expression,
"A right parenthesis is missing");
}
if (index == expression.length()) {
bloc = true;
}
}
return bloc;
}
/**
* Returns the operator and both expressions from a binary operation.
* @param expression the expression to split
* @return the list containing the operator, the left expression and
* the right expression. (in this order)
* @throws InvalidExpressionException if the expression is invalid
*/
private static List getExpressionsFromBinaryOperation(
final String expression) throws InvalidExpressionException {
List exp = new ArrayList();
int count = 0;
int i = 1;
int length = expression.length();
if (expression.startsWith(KeyWord.LEFT_PARENTHESIS.value())) {
count = 1;
char current;
while (i < length && count > 0) {
current = expression.charAt(i);
if (KeyWord.LEFT_PARENTHESIS.value().equals(String.valueOf(current))) {
count++;
} else if (
KeyWord.RIGHT_PARENTHESIS.value().equals(String.valueOf(current))) {
count--;
}
i++;
}
if (count > 0) {
throw new InvalidExpressionException(expression,
"A right parenthesis is missing");
}
} else {
i = 0;
char current;
String oper = "";
boolean op = false;
while (i < (length - 1) && !op) {
current = expression.charAt(i);
oper = String.valueOf(current);
if (oper.equals(KeyWord.AND.value()) || oper.equals(KeyWord.OR.value())
|| oper.equals(KeyWord.XOR.value())) {
op = true;
}
i++;
}
if (!op) {
throw new InvalidExpressionException(expression,
"Operator not valid");
}
i--;
}
String left = expression.substring(0, i);
String tail = expression.substring(i);
String operator = getOperator(tail);
int cut = tail.indexOf(operator);
String right = tail.substring(cut + operator.length(), tail.length());
exp.add(operator);
exp.add(left);
exp.add(right);
return exp;
}
/**
* Gets the first operator from the given expression.
* It can be a valid or an invalid operator.
* @param expression the expression
* @return the first operator
*/
private static String getOperator(String expression) {
expression = expression.trim();
String operator = expression.substring(0, 1);
if (expression.startsWith(KeyWord.LEFT_PARENTHESIS.value())
|| expression.startsWith(KeyWord.NOT.value())) {
operator = "";
} else if (!operator.equals(KeyWord.AND.value())
&& !operator.equals(KeyWord.OR.value())
&& !operator.equals(KeyWord.XOR.value())) {
int index = 0;
boolean end = false;
char c = 'a';
StringBuilder builder = new StringBuilder();
while (index < expression.length() && !end) {
c = expression.charAt(index);
builder.append(c);
if (Character.isWhitespace(c)) {
end = true;
}
index++;
}
operator = builder.toString();
}
return operator;
}
/**
* Checks whether the expression is a field.
* A field contains only a chain of letters and digits.
* @param expression the expression
* @return true if the expression is a field; false otherwise
*/
private static boolean isField(final String expression) {
int i = 0;
char ch = ' ';
boolean field = true;
while (i < expression.length() && field) {
ch = expression.charAt(i);
if (!Character.isJavaIdentifierPart(ch)) {
field = false;
}
i++;
}
return field;
}
/**
* Checks if the field is conform to the java field pattern:
* "^[a-z][a-zA-Z0-9]*$".
* @param expression the expression
* @return true if this expression matches this pattern; false otherwise
*/
private static boolean isConformField(final String expression) {
return expression.matches(JAVA_FIELD_PATTERN);
}
/**
* Gets an formatted expression. Tab, newline and carriage-return characters
* are replaced by a space character.
* @param expression
* @return
*/
private static String formatExpression(String expression) {
expression = expression.replaceAll("\t", " ");
expression = expression.replaceAll("\n", " ");
return expression.replaceAll("\r", " ");
}
public List getTokens() {
return tokens;
}
}
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