Utility to get from a Java Map/List/array using "path" expression

DPathUtils.java

package ddth.dasp.framework.utils;

import java.util.List;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class DPathUtils {

	private final static Pattern PATTERN_INDEX = Pattern
			.compile("^\\[(\\d+)\\]$");

	/**
	 * Extracts a value from a target object using DPath expression.
	 * 
	 * @param target
	 * @param dPath
	 */
	public static Object getValue(Object target, String dPath) {
		String[] paths = dPath.split("\\.");
		Object result = target;
		for (String path : paths) {
			result = extractValue(result, path);
		}
		return result;
	}

	private static Object extractValue(Object target, String index) {
		if (target == null) {
			throw new IllegalArgumentException();
		}
		Matcher m = PATTERN_INDEX.matcher(index);
		if (m.matches()) {
			int i = Integer.parseInt(m.group(1));
			if (target instanceof Object[]) {
				return ((Object[]) target)[i];
			}
			if (target instanceof List<?>) {
				return ((List<?>) target).get(i);
			}
			throw new IllegalArgumentException("Expect an array or list!");
		}
		if (target instanceof Map<?, ?>) {
			return ((Map<?, ?>) target).get(index);
		}
		throw new IllegalArgumentException();
	}
}