*  @param expression A valid XPath string.
     *  @return An XPathEvaluationResult, which can be used to obtain a string, number, nodelist, etc, should never be null.
     *
     * @throws XPathExpressionException if an XPath expression error occurs.
     */
    public XPathEvaluationResult<?> eval(final Node contextNode, final String expression) throws XPathExpressionException {

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.regex.Pattern;
import java.util.stream.Collectors;

import javax.xml.xpath.XPathEvaluationResult;
import javax.xml.xpath.XPathException;
import javax.xml.xpath.XPathNodes;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.codelibs.core.lang.StringUtil;

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

import javax.xml.xpath.XPathEvaluationResult;
import javax.xml.xpath.XPathException;
import javax.xml.xpath.XPathNodes;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.codelibs.core.beans.util.BeanUtil;

import java.util.Locale;
import java.util.Map;
import java.util.Set;
import java.util.function.UnaryOperator;
import java.util.stream.Collectors;
import java.util.stream.Stream;

import javax.xml.xpath.XPathEvaluationResult;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathNodes;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.codelibs.core.io.InputStreamUtil;