Bug 123840 Incorrect use of static fields in NEvaluator and FilterPassController
Data Engine classes org.eclipse.birt.data.engine.script.NEvaluator and FilterPassController (used for top-n and bottom-n filter process) use static class fields to store proessing data. This is not multi-thread safe. If there are concurrent requests running in the same JVM (even if they use different instances of DataEngine), data corruption will occur since multiple requests may get/set the static fields at the same time. These classes should keep all per-request data in instance fields. Each report query need to have its own instance.
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/script/ScriptEvalUtil.java
{
		if ( obj == null )
			return false;
		try
		{
			return DataTypeUtil.toBoolean( obj ).equals( bln );
		}
		catch ( BirtException e )
		{
			return false;
		}
	}
	
	private static Pattern s_JSReExprPattern;
	
	
	
	private static Matcher getJSReExprPatternMatcher( String patternStr )
	{
		if ( s_JSReExprPattern == null )
			s_JSReExprPattern = Pattern.compile("^/(.*)/([a-zA-Z]*)$");
		return s_JSReExprPattern.matcher( patternStr );
	}
	
	private static boolean match( Object source, Object pattern ) throws DataException
	{
		String sourceStr = (source == null)? "": source.toString();
		String patternStr = ( pattern == null )? "" : pattern.toString();