RegexpConsideration.java

package org.jboss.seam.remoting.validation;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;
import java.util.regex.Pattern;

import javax.validation.constraints.Pattern.Flag;

/**
 * some basic incompatibility between Java and JavaScript Regular Expression syntax is handled here
 * however since Java regular expression is relatively more powerful than JavaScript counterpart
 * it is developer's responsibility to make sure the provided Regular Expression is a valid
 * JS expression as well.
 * the main features that are not supported by JavaScript regular expression engines are:
 * <ul>
 * <li> No Unicode categories or blocks [just unicode characters]</li>
 * <li> No Character class Union, Intersection or substraction [simply no nesting and no &&] </li>
 * <li> No Possessive Quantifiers
 * </ul>
 *
 * @author Amir Sadri
 */
public class RegexpConsideration implements SpecialConsideration {

    private final static Pattern BACKSLASH_REPLACEMENT = Pattern.compile("\\\\\\\\");
    private final static Pattern PERMANENT_START_REPLACEMENT = Pattern.compile("\\\\A");
    private final static Pattern PERMANENT_END_REPLACEMENT = Pattern.compile("\\\\Z");


    public HashMap<String, Object> reassessParameters(Map<String, Object> constraintParams) {
        HashMap<String, Object> params = new HashMap<String, Object>();
        params.put("regexp", convertRegex((String) constraintParams.get("regexp")));
        Flag[] flags = (Flag[]) constraintParams.get("flags");
        int[] values = new int[flags.length];
        for (int i = 0; i < values.length; i++)
            values[i] = flags[i].getValue();

        ArrayList<String> changedFlags = convertRegexFlags(values);
        if (changedFlags.size() > 0)
            params.put("flags", changedFlags);

        return params;
    }

    public String reassessConstraintName(String constraintName) {
        return constraintName;
    }

    public final static String convertRegex(String regex) {
        regex = BACKSLASH_REPLACEMENT.matcher(regex).replaceAll("\\");
        //////// JavaScript doesn't support \A and \Z anchors, so we just replace them with '^' and '$'
        //////// although this strategy could easily get broken when multi-line flag is on
        regex = PERMANENT_START_REPLACEMENT.matcher(regex).replaceAll("^");
        regex = PERMANENT_END_REPLACEMENT.matcher(regex).replaceAll("$");
        ///// Matcher.matches()[which is what I am assuming we are all used to]
        ///// treats Regexps a little different than JS test() method does, so here I just try to make sure
        ///// that we are in the same page in both client and server side

        if (regex.charAt(0) != '^')
            regex = "^" + regex;
        if (regex.charAt(regex.length() - 1) != '$')
            regex += "$";

        return regex;
    }

    public final static ArrayList<String> convertRegexFlags(int[] flags) {
        ArrayList<String> jsFlags = new ArrayList<String>();
        for (int flag : flags) {
            switch (flag) {

                case java.util.regex.Pattern.CASE_INSENSITIVE:
                    jsFlags.add("i");
                    break;
                case java.util.regex.Pattern.MULTILINE:
                    jsFlags.add("m");
                    break;

            }
        }
        return jsFlags;
    }


}