validating using parser

[Eyal Golan]

Hello,
We have a situation which we need to check if an in-house filter is valid.
valid input can be something like the following:
(Location=Cayman) or (&(Location=Cayman)(Organization=Finance))
There are more options, but this is the basic.

We have a code that checks if the input is valid:

   
	public int isValidFilter(String filter){
		int result;
		try{
			filter = filter.replaceAll(" ", "");
			boolean check = true;
			boolean inExpression = false, toCheck = false;
			int count = 0, i = 1;
			char[] chars = filter.toCharArray();
			if(chars.length == 0){
				result = 0;
			}else{
				check &= chars[0] == '(';
				if(check){
					i = chars.length-1;
					check &= chars[chars.length-1] == ')';
					if(check){
						for(i = 0; i < chars.length && check; i++){
							if(inExpression && (chars[i] == '=' || chars[i] == '>' || chars[i] == '<')) inExpression = false;
							if(toCheck){
								if(chars[i] != AND && chars[i] != OR && chars[i] != NOT && chars[i] != APPROVER && chars[i] != APPROVER_LINK){
									inExpression = true;
								}
								toCheck = false;
							}
							if(chars[i] == '('){ 
								count++;
								toCheck = true;
							}
							if(chars[i] == ')'){
								check &= !inExpression;
								if(!(i == chars.length-1)){
									check &= (chars[i+1] == ')' || chars[i+1] == '(');
								}
								count--;
							}
						}
					}
				}
			}
			check &= count == 0;
			if(check) result = 0;
			else result = i;
		}catch(Exception ex){
			result = -1;
		}
		return result;
	}

 

The problem happens when a field consists with chars like '('.
I want to create something that uses the Pattern class.

Is it possible?

[Ulf Dittmer]

If this was my problem I'd write a lexer for the syntax, using a library like JFlex. They make for much more maintainable code for handling custom formats like these.

[Eyal Golan]

Thanks Ulf.
I'm looking into it.
It's a topic I haven't worked with it yet.

[Ulf Dittmer]

If I may strut my own stuff, here's an introductory article I wrote on using lexers: Handling Uncommon File Formats - Introducing Lexers.