predicate.java.svn-base

j2me mobile application for upload file to server.

package minixpath;
import java.util.Enumeration;
import java.util.Vector;

import org.kxml2.kdom.Element;

/**
 * @author Cosmin
 *
 * since I don't want to implement a full-blown xpath engine
 * our predicate 
 */
public class Predicate 
{
	Vector resultSet;

	Predicate(Vector inNodeSet, String predicateExpr)
	{
		int nodeIndex = -1;
		
		if(predicateExpr == null || predicateExpr.length() <= 0) {
			resultSet = inNodeSet;
			return;
		} else //we need to parse predicateExpr
			resultSet = new Vector();
		//check if this predicate is just a logical condition or a complete XPath query.
		//for now we support only logical conditions
		/*If it is a complete XPath expression
		{
			ResultSet = (new XPathExpression(XML_DOM, XPath Expression))
				.getResult();
		}//If it is a complete XPath expression */
		try {
			nodeIndex = Integer.parseInt(predicateExpr);
		} catch(NumberFormatException nfe) {
			//we do nothing, the predicate was not an index
		}
		
		if(nodeIndex != -1) {
			resultSet.addElement(inNodeSet.elementAt(nodeIndex));
			return;
		}
		
		String operation = null;
		int index = -1;
				
		if((index = predicateExpr.indexOf("=")) != -1) {
			operation = "=";
		} else if((index = predicateExpr.indexOf("<")) != -1) {
			operation = "<";
		} else if((index = predicateExpr.indexOf(">")) != -1) {
			operation = ">";
		} else {
			//shouldn't be here
			return;
		}
		Member member1 = new Member(new String(predicateExpr.toCharArray(), 0, index));
		Member member2 = new Member(new String(predicateExpr.toCharArray(), index+1, predicateExpr.length()-index-1));

		for(Enumeration e = inNodeSet.elements(); e.hasMoreElements(); ) {
			Object obj = e.nextElement();
			
			if(operation.equals("="))
				if(!member1.eval(obj).equals(member2.eval(obj)))
					continue;
			else if(operation.equals(">"))
				if(member1.eval(obj).compareTo(member2.eval(obj))<0)
					continue;
			else if(operation.equals("<"))
				if(member1.eval(obj).compareTo(member2.eval(obj))>0)
					continue;
			resultSet.addElement(obj);					
		}		
		
		//here we should start parsing the predicateExpr
	}//constructor

	class Member 
	{
		String m = null;
		String attribute = null;
		
		Member(String op)
		{
			this.m = op;
			
			if(op.startsWith("@")) {
				attribute = new String(op.toCharArray(), 1, op.length()-1);
			}
		}
		
		public String eval(Object obj) 
		{
			if(attribute == null)
				return m;
			
			if(!(obj instanceof Element))
				return "";
			
			Element element = (Element)obj;
			String attr = element.getAttributeValue(null, attribute);
			
			return attr!=null?attr:"";
		}
	}
		
	public Vector getResult()
	{
		return resultSet;
	}//getResult
}