Domain name regular expression example
Domain Name Regular Expression Pattern
^((?!-)[A-Za-z0-9-]{1,63}(?<!-)\\.)+[A-Za-z]{2,6}$Above pattern makes sure domain name matches the following criteria :
The domain name should be a-z | A-Z | 0-9 and hyphen(-)
The domain name should between 1 and 63 characters long
Last Tld must be at least two characters, and a maximum of 6 characters
The domain name should not start or end with hyphen (-) (e.g. -google.com or google-.com)
The domain name can be a subdomain (e.g. mkyong.blogspot.com)
Description
^ #Start of the line
( #Start of group #1
(?! -) #Can't start with a hyphen
[A-Za-z0-9-]{1,63} #Domain name is [A-Za-z0-9-], between 1 and 63 long
(?<!-) #Can't end with hyphen
\\. #Follow by a dot "."
)+ #End of group #1, this group must appear at least 1 time, but allowed multiple times for subdomain
[A-Za-z]{2,6} #TLD is [A-Za-z], between 2 and 6 long
$ #end of the lineNote
This regular expression pattern should be able to match most of the "real-working" domain names.
List of valid domain names
www.google.com
google.com
mkyong123.com
mkyong-info.com
sub.mkyong.com
sub.mkyong-info.com
mkyong.com.au
g.co
mkyong.t.t.co
List of invalid domain names, and why.
mkyong.t.t.c - Tld must between 2 and 6 long
mkyong,com - Comma is not allow
mkyong - No Tld
mkyong.123 , Tld not allow digit
.com - Must start with [A-Za-z0-9]
mkyong.com/users - No Tld
-mkyong.com - Cannot begin with a hyphen -
mkyong-.com - Cannot end with a hyphen -
sub.-mkyong.com - Cannot begin with a hyphen -
sub.mkyong-.com - Cannot end with a hyphen -
1. Java Regular Expression Example
A simple Java example to validate a domain name with above regular expressions pattern.
DomainUtils.java
package com.mkyong.regex;
import java.util.HashSet;
import java.util.Set;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class DomainUtils {
private static Pattern pDomainNameOnly;
private static final String DOMAIN_NAME_PATTERN = "^((?!-)[A-Za-z0-9-]{1,63}(?<!-)\\.)+[A-Za-z]{2,6}$";
static {
pDomainNameOnly = Pattern.compile(DOMAIN_NAME_PATTERN);
public static boolean isValidDomainName(String domainName) {
return pDomainNameOnly.matcher(domainName).find();2. Unit Test with jUnit
A jUnit example.
DomainUtilsTestParam.java
package com.mkyong.regex;
import static org.junit.Assert.assertEquals;
import java.util.Arrays;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.junit.runners.Parameterized;
import org.junit.runners.Parameterized.Parameters;
@RunWith(value = Parameterized.class)
public class DomainUtilsTestParam {
private String domain;
private boolean expected;
public DomainUtilsTestParam(String domain, boolean expected) {
this.domain = domain;
this.expected = expected;
@Parameters(name= "{index}: isValid({0})={1}")
public static Iterable<Object[]> data() {
return Arrays.asList(new Object[][] {
{ "www.google.com", true },
{ "google.com", true },
{ "mkyong123.com", true },
{ "mkyong-info.com", true },
{ "sub.mkyong.com", true },
{ "sub.mkyong-info.com", true },
{ "mkyong.com.au", true },
{ "sub.mkyong.com", true },
{ "sub.sub.mkyong.com", true },
{ "g.co", true },
{ "mkyong.t.t.co", true },
{ "mkyong.t.t.c", false }, //Tld must at between 2 and 6 long
{ "mkyong,com", false }, //comma not allowed
{ "mkyong", false }, //no tld
{ "mkyong.123", false }, //digit not allowed in tld
{ ".com", false }, //must start with [A-Za-z0-9]
{ "mkyong.a", false }, //last tld need at least two characters
{ "mkyong.com/users", false }, // no tld
{ "-mkyong.com", false }, //Cannot begin with a hyphen -
{ "mkyong-.com", false }, //Cannot end with a hyphen -
{ "sub.-mkyong.com", false }, //Cannot begin with a hyphen -
{ "sub.mkyong-.com", false } //Cannot end with a hyphen -
);
@Test
public void test_validDomains() {
assertEquals(expected,DomainUtils.isValidDomainName(domain));Output, all passed.
4. Unit Test with TestNG
A TestNG example.
DomainUtilsTestParam.java
package com.mkyong.regex;
import org.testng.Assert;
import org.testng.annotations.DataProvider;
import org.testng.annotations.Test;
public class DomainUtilsTestParam {
@DataProvider
public Object[][] ValidDomainNameProvider() {
return new Object[][] {{
new String[] {
"www.google.com", "google.com",
"mkyong123.com", "mkyong-info.com",
"sub.mkyong.com","sub.mkyong-info.com",
"mkyong.com.au", "sub.mkyong.com",
"sub.sub.mkyong.com", "g.co", "mkyong.t.t.co" } } };
@DataProvider
public Object[][] InvalidDomainNameProvider() {
return new Object[][] { { new String[] {
"mkyong.t.t.c", "mkyong,com",
"mkyong", "mkyong.123",
".com", "mkyong.a",
"mkyong.com/users", "-mkyong.com",
"mkyong-.com",".com", "sub.-mkyong.com", "sub.mkyong-.com"} } };
@Test(dataProvider = "ValidDomainNameProvider")
public void ValidDomainNameTest(String[] domainName) {
for (String temp : domainName) {
boolean valid = DomainUtils.isValidDomainName(temp);
System.out.println("Valid domain name : " + temp);
Assert.assertEquals(valid, true);
@Test(dataProvider = "InvalidDomainNameProvider",
dependsOnMethods = "ValidDomainNameTest")
public void InValidDomainNameTest(String[] domainName) {
for (String temp : domainName) {
boolean valid = DomainUtils.isValidDomainName(temp);
System.out.println("Invalid domain name : " + temp);
Assert.assertEquals(valid, false);Result
Valid domain name : www.google.com Valid domain name : google.com Valid domain name : mkyong123.com Valid domain name : mkyong-info.com Valid domain name : sub.mkyong.com Valid domain name : sub.mkyong-info.com Valid domain name : mkyong.com.au Valid domain name : sub.mkyong.com Valid domain name : sub.sub.mkyong.com Valid domain name : g.co Valid domain name : mkyong.t.t.co Invalid domain name : mkyong.t.t.c Invalid domain name : mkyong,com Invalid domain name : mkyong Invalid domain name : mkyong.123 Invalid domain name : .com Invalid domain name : mkyong.a Invalid domain name : mkyong.com/users Invalid domain name : -mkyong.com Invalid domain name : mkyong-.com Invalid domain name : .com Invalid domain name : sub.-mkyong.com Invalid domain name : sub.mkyong-.com PASSED: ValidDomainNameTest([Ljava.lang.String;@4661e987) PASSED: InValidDomainNameTest([Ljava.lang.String;@117b8cf0) =============================================== Default test Tests run: 2, Failures: 0, Skips: 0 ===============================================
References
From：一号门
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