com.google.common.net
Class InternetDomainName

java.lang.Object
  com.google.common.net.InternetDomainName

@Beta
@GwtCompatible(emulated=true)
public final class InternetDomainName
extends Object

An immutable well-formed internet domain name, as defined by RFC 1035. Examples include com and foo.co.uk. Only syntactic analysis is performed; no DNS lookups or other network interactions take place. Thus there is no guarantee that the domain actually exists on the internet. Invalid domain names throw IllegalArgumentException on construction.

One common use of this class is to determine whether a given string is likely to represent an addressable domain on the web -- that is, for a candidate string "xxx", might browsing to "http://xxx/" result in a webpage being displayed? In the past, this test was frequently done by determining whether the domain ended with a public suffix but was not itself a public suffix. However, this test is no longer accurate; there are many domains which are both public suffixes and addressable as hosts. "uk.com" is one example. As a result, the only useful test to determine if a domain is a plausible web host is hasPublicSuffix(). This will return true for many domains which (currently) are not hosts, such as "com"), but given that any public suffix may become a host without warning, it is better to err on the side of permissiveness and thus avoid spurious rejection of valid sites.

Equality of domain names is case-insensitive with respect to ASCII characters, so for convenience, the name() and parts() methods return string with all ASCII characters converted to lowercase.

internationalized domain names such as 网络.cn are supported, but with much weaker syntactic validation (resulting in false positive reports of validity).

Since:

5

Author:

Craig Berry

Method Summary

InternetDomainName	child(String leftParts) Creates and returns a new InternetDomainName by prepending the argument and a dot to the current name.
boolean	equals(Object object)
static InternetDomainName	from(String domain) A factory method for creating InternetDomainName objects.
int	hashCode()
boolean	hasParent() Indicates whether this domain is composed of two or more parts.
boolean	hasPublicSuffix() Indicates whether this domain name ends in a public suffix, including if it is a public suffix itself.
boolean	isPublicSuffix() Indicates whether this domain name represents a public suffix, as defined by the Mozilla Foundation's Public Suffix List (PSL).
boolean	isTopPrivateDomain() Indicates whether this domain name is composed of exactly one subdomain component followed by a public suffix.
boolean	isUnderPublicSuffix() Indicates whether this domain name ends in a public suffix, while not being a public suffix itself.
static boolean	isValid(String name) Indicates whether the argument is a syntactically valid domain name.
String	name() Returns the domain name, normalized to all lower case.
InternetDomainName	parent() Returns an InternetDomainName that is the immediate ancestor of this one; that is, the current domain with the leftmost part removed.
ImmutableList<String>	parts() Returns the individual components of this domain name, normalized to all lower case.
InternetDomainName	publicSuffix() Returns the public suffix portion of the domain name, or null if no public suffix is present.
InternetDomainName	topPrivateDomain() Returns the portion of this domain name that is one level beneath the public suffix.
String	toString()

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Method Detail

from

public static InternetDomainName from(String domain)

A factory method for creating InternetDomainName objects.

Parameters:

domain - A domain name (not IP address)

Throws:

IllegalArgumentException - If name is not syntactically valid

name

public String name()

Returns the domain name, normalized to all lower case.

parts

public ImmutableList<String> parts()

Returns the individual components of this domain name, normalized to all lower case. For example, for the domain name mail.google.com, this method returns the list ["mail", "google", "com"].

isPublicSuffix

public boolean isPublicSuffix()

Indicates whether this domain name represents a public suffix, as defined by the Mozilla Foundation's Public Suffix List (PSL). A public suffix is one under which Internet users can directly register names, such as com, co.uk or pvt.k12.wy.us. Examples of domain names that are not public suffixes include google, google.com and foo.co.uk.

Returns:

true if this domain name appears exactly on the public suffix list

Since:

6

hasPublicSuffix

public boolean hasPublicSuffix()

Indicates whether this domain name ends in a public suffix, including if it is a public suffix itself. For example, returns true for www.google.com, foo.co.uk and com, but not for google or google.foo. This is the recommended method for determining whether a domain is potentially an addressable host.

Since:

6

publicSuffix

public InternetDomainName publicSuffix()

Returns the public suffix portion of the domain name, or null if no public suffix is present.

Since:

6

isUnderPublicSuffix

public boolean isUnderPublicSuffix()

Indicates whether this domain name ends in a public suffix, while not being a public suffix itself. For example, returns true for www.google.com, foo.co.uk and bar.ca.us, but not for google, com, or google.foo.

Warning: a false result from this method does not imply that the domain does not represent an addressable host, as many public suffixes are also addressable hosts. Use hasPublicSuffix() for that test.

This method can be used to determine whether it will probably be possible to set cookies on the domain, though even that depends on individual browsers' implementations of cookie controls. See RFC 2109 for details.

Since:

6

isTopPrivateDomain

public boolean isTopPrivateDomain()

Indicates whether this domain name is composed of exactly one subdomain component followed by a public suffix. For example, returns true for google.com and foo.co.uk, but not for www.google.com or co.uk.

Warning: A true result from this method does not imply that the domain is at the highest level which is addressable as a host, as many public suffixes are also addressable hosts. For example, the domain bar.uk.com has a public suffix of uk.com, so it would return true from this method. But uk.com is itself an addressable host.

This method can be used to determine whether a domain is probably the highest level for which cookies may be set, though even that depends on individual browsers' implementations of cookie controls. See RFC 2109 for details.

Since:

6

topPrivateDomain

public InternetDomainName topPrivateDomain()

Returns the portion of this domain name that is one level beneath the public suffix. For example, for x.adwords.google.co.uk it returns google.co.uk, since co.uk is a public suffix.

If isTopPrivateDomain() is true, the current domain name instance is returned.

This method should not be used to determine the topmost parent domain which is addressable as a host, as many public suffixes are also addressable hosts. For example, the domain foo.bar.uk.com has a public suffix of uk.com, so it would return bar.uk.com from this method. But uk.com is itself an addressable host.

This method can be used to determine the probable highest level parent domain for which cookies may be set, though even that depends on individual browsers' implementations of cookie controls.

Throws:

IllegalStateException - if this domain does not end with a public suffix

Since:

6

hasParent

public boolean hasParent()

Indicates whether this domain is composed of two or more parts.

parent

public InternetDomainName parent()

Returns an InternetDomainName that is the immediate ancestor of this one; that is, the current domain with the leftmost part removed. For example, the parent of www.google.com is google.com.

Throws:

IllegalStateException - if the domain has no parent, as determined by hasParent()

child

public InternetDomainName child(String leftParts)

Creates and returns a new InternetDomainName by prepending the argument and a dot to the current name. For example, InternetDomainName.from("foo.com").child("www.bar") returns a new InternetDomainName with the value www.bar.foo.com.

Throws:

NullPointerException - if leftParts is null

IllegalArgumentException - if the resulting name is not valid

isValid

public static boolean isValid(String name)

Indicates whether the argument is a syntactically valid domain name. This method is intended for the case where a String must be validated as a valid domain name, but no further work with that String as an InternetDomainName will be required. Code like the following will unnecessarily repeat the work of validation:

   if (InternetDomainName.isValid(name)) {
     domainName = InternetDomainName.from(name);
   } else {
     domainName = DEFAULT_DOMAIN;
   }

Such code could instead be written as follows:

   try {
     domainName = InternetDomainName.from(name);
   } catch (IllegalArgumentException e) {
     domainName = DEFAULT_DOMAIN;
   }

toString

public String toString()

Overrides:

toString in class Object

equals

public boolean equals(@Nullable
                      Object object)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object