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. (e-mail address removed)
* No "Roedy Green" <
[email protected]> style
addresses.
* No local addresses, eg. roedy.
*
* @return 0 = email address is definitely malformed, e.g. missing
@.
* ends in .invalid
* <br>
* 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.
* <br>
* 2 = unknown top level domain.
* <br>
* 3 = dots at beginning or end, doubled in name.
* <br>
* 4 = address of form xxx@[209.139.205.2] using IP
* <br>
* 5 = address of form (e-mail address removed) Dots _ or
- in first part of name
* <br>
* 6 = addreess of form (e-mail address removed) rare, but known,
domain
* <br>
* 7 = address of form (e-mail address removed) or any national
suffix.
* <br>
* 8 = address of form (e-mail address removed) the matching this
national suffix,
* e.g. .ca in Canada, .de in Germany
* <br>
* 9 = address of form (e-mail address removed) .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
.startsWith("_") ||
fragments.endsWith("_") ||
fragments.startsWith("-") ||
fragments.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);
}
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("[email protected]"));
}
} // end class EmailSyntaxValidator