Package com.google.common.net

Class InternetDomainName

  • @Beta
@GwtCompatible
public final class InternetDomainName
extends java.lang.Object
    An immutable well-formed internet domain name, such as com or 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.

    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.

    During construction, names are normalized in two ways:

    1. ASCII uppercase characters are converted to lowercase.
    2. Unicode dot separators other than the ASCII period ('.') are converted to the ASCII period.

    The normalized values will be returned from name() and parts(), and will be reflected in the result of equals(Object).

    Internationalized domain names such as 网络.cn are supported, as are the equivalent IDNA Punycode-encoded versions.

    Since:
    5.0

    • Method Detail

      • fromLenient

        @Deprecated
public static InternetDomainName fromLenient​(java.lang.String domain)
        Deprecated.
        Use from(String)
        A deprecated synonym for from(String).
        Parameters:
        domain - A domain name (not IP address)
        Throws:
        java.lang.IllegalArgumentException - if name is not syntactically valid according to isValid(java.lang.String)
        Since:
        8.0 (previously named from)

      • from

        public static InternetDomainName from​(java.lang.String domain)
        Returns an instance of InternetDomainName after lenient validation. Specifically, validation against RFC 3490 ("Internationalizing Domain Names in Applications") is skipped, while validation against RFC 1035 is relaxed in the following ways:
        • Any part containing non-ASCII characters is considered valid.
        • Underscores ('_') are permitted wherever dashes ('-') are permitted.
        • Parts other than the final part may start with a digit.
        Parameters:
        domain - A domain name (not IP address)
        Throws:
        java.lang.IllegalArgumentException - if name is not syntactically valid according to isValid(java.lang.String)
        Since:
        10.0 (previously named fromLenient)

      • name

        @Deprecated
public java.lang.String name()
        Deprecated.
        Use toString()
        A deprecated synonym for toString().

      • parts

        public ImmutableList<java.lang.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:
        6.0

      • 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:
        6.0

      • publicSuffix

        public InternetDomainName publicSuffix()
        Returns the public suffix portion of the domain name, or null if no public suffix is present.
        Since:
        6.0

      • 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:
        6.0

      • 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:
        6.0

      • 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:
        java.lang.IllegalStateException - if this domain does not end with a public suffix
        Since:
        6.0

      • 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:
        java.lang.IllegalStateException - if the domain has no parent, as determined by hasParent()

      • child

        public InternetDomainName child​(java.lang.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. Only lenient validation is performed, as described here.
        Throws:
        java.lang.NullPointerException - if leftParts is null
        java.lang.IllegalArgumentException - if the resulting name is not valid

      • isValid

        public static boolean isValid​(java.lang.String name)
        Indicates whether the argument is a syntactically valid domain name using lenient validation. Specifically, validation against RFC 3490 ("Internationalizing Domain Names in Applications") is skipped.

        The following two code snippets are equivalent: 

           
   domainName = InternetDomainName.isValid(name)
       ? InternetDomainName.from(name)
       : DEFAULT_DOMAIN;
           
   try {
     domainName = InternetDomainName.from(name);
   } catch (IllegalArgumentException e) {
     domainName = DEFAULT_DOMAIN;
   }
        Since:
        8.0 (previously named isValidLenient)

      • toString

        public java.lang.String toString()
        Returns the domain name, normalized to all lower case.
        Overrides:
        toString in class java.lang.Object

      • equals

        public boolean equals​(@Nullable
                      java.lang.Object object)
        Equality testing is based on the text supplied by the caller, after normalization as described in the class documentation. For example, a non-ASCII Unicode domain name and the Punycode version of the same domain name would not be considered equal.
        Overrides:
        equals in class java.lang.Object

      • hashCode

        public int hashCode()
        Overrides:
        hashCode in class java.lang.Object