/*
* JBoss, Home of Professional Open Source.
* Copyright 2006, Red Hat Middleware LLC, and individual contributors
* as indicated by the @author tags. See the copyright.txt file in the
* distribution for a full listing of individual contributors.
*
* This 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; either version 2.1 of
* the License, or (at your option) any later version.
*
* This software 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 software; if not, write to the Free
* Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
* 02110-1301 USA, or see the FSF site: http://www.fsf.org.
*/
package org.jboss.aspects.dbc.condition.parser;
/**
* A very simple expression parser, for the reason that I really,
* really cannot get my head around defining grammars in
* JavaCC. If this grammar gets more complex I guess JavaCC
* is the way forward...
*
* @author <a href="mailto:kabir.khan@jboss.org">Kabir Khan</a>
* @version $Revision: 57186 $
*/
public class ExpressionParser
{
static final String FORALL = "forall ";
static final String EXISTS = "exists ";
static final String IMPLIES = " implies ";
static final String JAVA = "java: ";
static final String IN = " in ";
static final String SEPARATOR = " | ";
public static Expression parseExpression(String expr)
{
return parse(expr);
}
private static Expression parse(String expr)
{
expr = expr.trim();
if (expr.startsWith(FORALL))
{
return parseForAll(expr);
}
else if (expr.startsWith(EXISTS))
{
return parseExists(expr);
}
else if (expr.indexOf(IMPLIES) > 0)
{
return parseImplies(expr);
}
else if (expr.startsWith(JAVA))
{
return parseJava(expr);
}
else
{
return parseBoolean(expr);
}
}
private static Expression parseForAll(String expr)
{
int in = expr.indexOf(IN);
if (in < 0) throw new RuntimeException("forall expressions must have an 'in' clause: " + expr);
String declaration = expr.substring(FORALL.length(), in);
int sep = expr.indexOf(SEPARATOR);
if (sep < 0) throw new RuntimeException("forall expressions must have a '|': " + expr);
String collection = expr.substring(in + IN.length(), sep);
String body = expr.substring(sep + SEPARATOR.length());
Expression sub = parse(body);
ForAllExpression forAll = new ForAllExpression(declaration, collection, sub);
return forAll;
}
private static Expression parseExists(String expr)
{
int in = expr.indexOf(IN);
if (in < 0) throw new RuntimeException("exists expressions must have an 'in' clause: " + expr);
String declaration = expr.substring(EXISTS.length(), in);
int sep = expr.indexOf(SEPARATOR);
if (sep < 0) throw new RuntimeException("exists expressions must have a '|': " + expr);
String collection = expr.substring(in + IN.length(), sep);
String body = expr.substring(sep + SEPARATOR.length());
Expression sub = parse(body);
ExistsExpression exists = new ExistsExpression(declaration, collection, sub);
return exists;
}
private static Expression parseImplies(String expr)
{
int impl = expr.indexOf(IMPLIES);
String exprA = expr.substring(0, impl);
String exprB = expr.substring(impl + IMPLIES.length());
if (exprA.trim().length() == 0 || exprB.trim().length() == 0)
{
throw new RuntimeException("implies expressions must take two simple boolean expressions: " + expr);
}
if (exprA.endsWith(";"))
{
exprA = expr.substring(0, expr.length() - 1);
}
try
{
Expression condA = parse(exprA);
Expression condB = parse(exprB);
ImpliesExpression implies = new ImpliesExpression((BooleanExpression)condA, (BooleanExpression)condB);
return implies;
}
catch (ClassCastException e)
{
throw new RuntimeException("implies expressions must take two simple boolean expressions: " + expr);
}
}
private static Expression parseJava(String expr)
{
expr = expr.substring(JAVA.length());
return new JavaExpression(expr);
}
private static Expression parseBoolean(String expr)
{
if (expr.endsWith(";"))
{
expr = expr.substring(0, expr.length() - 1);
}
return new BooleanExpression(expr);
}
public static void main(String[] args)
{
doit("a == b");
doit("a == b implies b == a");
doit("forall IEmployee e in getEmployees() | getRooms().contains(e.getOffice());");
doit("exists IEmployee e in getEmployees() | !getRooms().contains(e.getOffice())");
doit("forall IEmployee e1 in getEmployees() | forall IEmployee e2 in getEmployees() | (e1 != e2) implies e1.getOffice() != e2.getOffice()");
doit("java: for (int i = 0){i > 0;}");
}
public static void doit(String str)
{
System.out.println(str);
System.out.println();
Expression expr = ExpressionParser.parseExpression(str);
BeanshellGenerator gen = new BeanshellGenerator(expr);
System.out.println(gen.createBeanshellCode());
System.out.println("-----------------------");
}
}
|