Email regular expression validator - comp.lang.java.programmer

Could someone give me a java-based code example of an email validator using regular expressions ? I know that following the RFC to the letter will result in a very complicated expression. I'm not looking for that I only want to validate e-mails that "most of us" use. //linus nikander - linus@nikander.net

Linus Nikander wrote: > Could someone give me a java-based code example of an email validator > using regular expressions ? > > I know that following the RFC to the letter will result in a very > complicated expression. I'm not looking for that I only want to validate > e-mails that "most of us" use. > > //linus nikander - linus@nikander.net something like the following handles a lot of the cases (all the numbers are for handling of ip-adresses, eg. user@[123.122.123.1], which are valid, but very rare cases): ^([a-z0-9_\\-])+(\\.([a-z0-9_\\-])+)*@((\\[(((([0-1])?([0-9])?[0-9])|(2[0-4 [0-9])|(2[0-5][0-5])))\\.(((([0-1])?([0-9])?[0-9])|(2[0-4][0-9])|(2[0-5 [0-5])))\\.(((([0-1])?([0-9])?[0-9])|(2[0-4][0-9])|(2[0-5][0-5])))\\ (((([0-1])?([0-9])?[0-9])|(2[0-4][0-9])|(2[0-5][0-5]))\\]))|((([a-z0-9\\-] +\\.)+([a-z]{2}\\.[a-z]{2}|[a-z]{2,7})))$ You'd use it like this: Pattern pattern = Pattern.compile(regex); if(pattern.matcher(email).matches()) { //adress is valid } you should also check out http://regexlib.com/ , it is a good resource for regexes. -- mvg, Christophe Vanfleteren

On Fri, 19 Sep 2003 13:51:20 +0200, "Linus Nikander" <linus@nikander.net> wrote or quoted : >I know that following the RFC to the letter will result in a very >complicated expression. I'm not looking for that I only want to validate >e-mails that "most of us" use. package com.mindprod.bulk; import java.util.HashSet; import java.util.Locale; import java.util.regex.Matcher; import java.util.regex.Pattern; import javax.mail.internet.AddressException; import javax.mail.internet.InternetAddress; /** * Validate syntax of email addresses. * Does not probe to see if mailserver exists in DNS or online. * See MailProber for that. * See ValidateEmailFile for an example of how to use this class. * * @author Roedy Green, Canadian Mind Products * @version 1.0 * to do: check validity of & in first part of email address. Appears in practice. */ public class EmailSyntaxValidator { private static boolean debugging = false; /** * Check how likely an email address is to be valid. * The higher the number returned, the more likely the address is valid. * This method does not probe the internet in any way to see if * the corresponding mail server or domain exists. * * @param email bare computer email address. * e.g. roedy@mindprod.com * No "Roedy Green" <roedy@mindprod.com> style addresses. * No local addresses, eg. roedy. * * @return 0 = email address is definitely malformed, e.g. missing @. * ends in .invalid * * 1 = address does not meet one of the valid patterns below. * It still might be ok according to some obscure rule in RFC 822 * Java InternetAddress accepts it as valid. * * 2 = unknown top level domain. * * 3 = dots at beginning or end, doubled in name. * * 4 = address of form xxx@[209.139.205.2] using IP * * 5 = address of form xxx.xxx.xxx@xxx.xxx.xxx Dots _ or - in first part of name * * 6 = addreess of form xxx@xxx.xxx.xxx rare, but known, domain * * 7 = address of form xxx@xxx.xxx.ca or any national suffix. * * 8 = address of form xxx@xxx.xxx.xx the matching this national suffix, * e.g. .ca in Canada, .de in Germany * * 9 = address of form xxx@xxx.xxx.com .org .net .edu .gov ..biz -- official domains */ public static int howValid(String email) { if ( email == null ) { return 0; } email = email.trim().toLowerCase(); int dotPlace = email.lastIndexOf('.'); if ( 0 < dotPlace && dotPlace < email.length()-1 ) { /* have at least x.y */ String tld = email.substring(dotPlace+1); if ( badTLDs.contains(tld) ) { /* deliberate invalid address */ return 0; } // make sure none of fragments start or end in _ or - String[] fragments = splitter.split(email); boolean clean = true; for ( int i=0; i<fragments.length; i++ ) { if ( fragments[i].startsWith("_") || fragments[i].endsWith("_") || fragments[i].startsWith("-") || fragments[i].endsWith("-") ) { clean = false; break; } } // end for if ( clean ) { Matcher m9 = p9.matcher(email); if ( m9.matches() ) { if ( officialTLDs.contains(tld) ) return 9; else if ( thisCountry.equals(tld) ) return 8; else if ( nationalTLDs.contains(tld) ) return 7; else if ( rareTLDs.contains(tld) ) return 6; else return 3; /* unknown tld */ } // allow dots in name Matcher m5 = p5.matcher(email); if ( m5.matches() ) { if ( officialTLDs.contains(tld) ) return 5; else if ( thisCountry.equals(tld) ) return 5; else if ( nationalTLDs.contains(tld) ) return 5; else if ( rareTLDs.contains(tld) ) return 5; else return 2; /* unknown tld */ } // IP Matcher m4 = p4.matcher(email); if ( m4.matches() ) return 4; /* can't tell TLD */ // allow even lead/trail dots in name, except at start of domain Matcher m3 = p3.matcher(email); if ( m3.matches() ) { if ( officialTLDs.contains(tld) ) return 3; else if ( thisCountry.equals(tld) ) return 3; else if ( nationalTLDs.contains(tld) ) return 3; else if ( rareTLDs.contains(tld) ) return 3; else return 2; /* unknown domain */ } } // end if clean } // allow even unclean addresses, and addresses without a TLD to have a whack at passing RFC:822 try { /* see if InternetAddress likes it, it follows RFC:822. It will names without domains though. */ InternetAddress.parse(email, true /* strict */); // it liked it, no exception happened. Seems very sloppy. return 1; } catch ( AddressException e ) { // it did not like it return 0; } } // allow _ - in name, lead and trailing ones are filtered later, no +. static Pattern p9 = Pattern.compile("[a-z0-9\\-_]++@[a-z0-9\\-_]++(\\.[a-z0-9\\-_]++)++"); // to split into fields static Pattern splitter = Pattern.compile("[@\\.]"); // to allow - _ dots in name, no + static Pattern p5 = Pattern.compile("[a-z0-9\\-_]++(\\.[a-z0-9\\-_]++)*@[a-z0-9\\-_]++(\\.[a-z0-9\\-_]++)++"); // IP style names, no + static Pattern p4 = Pattern.compile("[a-z0-9\\-_]++(\\.[a-z0-9\\-_]++)*@\\[([0-9]{1,3}\\.){3}[0-9]{1,3}\\]"); // allow dots anywhere, but not at start of domain name, no + static Pattern p3 = Pattern.compile("[a-z0-9\\-_\\.]++@[a-z0-9\\-_]++(\\.[a-z0-9\\-_]++)++"); /** * build a HashSet from a array of String literals. * * @param list array of strings * @return HashSet you can use to test if a string is in the set. */ static HashSet hmaker(String[] list) { HashSet map = new HashSet(Math.max((int) (list.length/.75f) + 1, 16)); for ( int i=0; i<list.length; i++ ) { map.add(list[i]); } return map; } static final String thisCountry = Locale.getDefault().getCountry().toLowerCase(); static final HashSet officialTLDs = hmaker(new String[] { "aero", "biz", "coop", "com", "edu", "gov", "info", "mil", "museum", "name", "net", "org", "pro", }); static final HashSet rareTLDs = hmaker(new String[] { "cam", "mp3", "agent", "art", "arts", "asia", "auction", "aus", "bank", "cam", "chat", "church", "club", "corp", "dds", "design", "dns2go", "e", "email", "exp", "fam", "family", "faq", "fed", "film", "firm", "free", "fun", "g", "game", "games", "gay", "ger", "globe", "gmbh", "golf", "gov", "help", "hola", "i", "inc", "int", "jpn", "k12", "kids", "law", "learn", "llb", "llc", "llp", "lnx", "love", "ltd", "mag", "mail", "med", "media", "mp3", "netz", "nic", "nom", "npo", "per", "pol", "prices", "radio", "rsc", "school", "scifi", "sea", "service", "sex", "shop", "sky", "soc", "space", "sport", "tech", "tour", "travel", "usvi", "video", "web", "wine", "wir", "wired", "zine", "zoo", }); static final HashSet nationalTLDs = hmaker(new String[] { "ac", "ad", "ae", "af", "ag", "ai", "al", "am", "an", "ao", "aq", "ar", "as", "at", "au", "aw", "az", "ba", "bb", "bd", "be", "bf", "bg", "bh", "bi", "bj", "bm", "bn", "bo", "br", "bs", "bt", "bv", "bw", "by", "bz", "ca", "cc", "cd", "cf", "cg", "ch", "ci", "ck", "cl", "cm", "cn", "co", "cr", "cu", "cv", "cx", "cy", "cz", "de", "dj", "dk", "dm", "do", "dz", "ec", "ee", "eg", "eh", "er", "es", "et", "fi", "fj", "fk", "fm", "fo", "fr", "fx", "ga", "gb", "gd", "ge", "gf", "gg", "gh", "gi", "gl", "gm", "gn", "gp", "gq", "gr", "gs", "gt", "gu", "gw", "gy", "hk", "hm", "hn", "hr", "ht", "hu", "id", "ie", "il", "im", "in", "io", "iq", "ir", "is", "it", "je", "jm", "jo", "jp", "ke", "kg", "kh", "ki", "km", "kn", "kp", "kr", "kw", "ky", "kz", "la", "lb", "lc", "li", "lk", "lr", "ls", "lt", "lu", "lv", "ly", "ma", "mc", "md", "mg", "mh", "mk", "ml", "mm", "mn", "mo", "mp", "mq", "mr", "ms", "mt", "mu", "mv", "mw", "mx", "my", "mz", "na", "nc", "ne", "nf", "ng", "ni", "nl", "no", "np", "nr", "nu", "nz", "om", "pa", "pe", "pf", "pg", "ph", "pk", "pl", "pm", "pn", "pr", "ps", "pt", "pw", "py", "qa", "re", "ro", "ru", "rw", "sa", "sb", "sc", "sd", "se", "sg", "sh", "si", "sj", "sk", "sl", "sm", "sn", "so", "sr", "st", "sv", "sy", "sz", "tc", "td", "tf", "tg", "th", "tj", "tk", "tm", "tn", "to", "tp", "tr", "tt", "tv", "tw", "tz", "ua", "ug", "uk", "um", "us", "uy", "uz", "va", "vc", "ve", "vg", "vi", "vn", "vu", "wf", "ws", "ye", "yt", "yu", "za", "zm", "zw", }); static final HashSet badTLDs = hmaker(new String[] { "invalid", "nowhere", "noone", }); public static void main (String[] args) { System.out.println(howValid("kellizer@.hotmail.com")); } } // end class EmailSyntaxValidator -- Canadian Mind Products, Roedy Green. Coaching, problem solving, economical contract programming. See http://mindprod.com/jgloss/jgloss.html for The Java Glossary.