public final class IDN extends Object
Internationalized domain names are defined in RFC 3490. RFC 3490 defines two operations: ToASCII and ToUnicode. These 2 operations employ Nameprep algorithm, which is a profile of Stringprep, and Punycode algorithm to convert domain name string back and forth.
The behavior of aforementioned conversion process can be adjusted by various flags:
The security consideration is important with respect to internationalization domain name support. For example, English domain names may be homographed - maliciously misspelled by substitution of non-Latin letters. Unicode Technical Report #36 discusses security issues of IDN support as well as possible solutions. Applications are responsible for taking adequate security measures when using international domain names.
Modifier and Type | Field | Description |
---|---|---|
static final int |
ALLOW_UNASSIGNED |
Flag to allow processing of unassigned code points |
static final int |
USE_STD3_ASCII_RULES |
Flag to turn on the check against STD-3 ASCII rules |
Modifier and Type | Method | Description |
---|---|---|
static String |
toASCII |
Translates a string from Unicode to ASCII Compatible Encoding (ACE), as defined by the ToASCII operation of RFC 3490. |
static String |
toASCII |
Translates a string from Unicode to ASCII Compatible Encoding (ACE), as defined by the ToASCII operation of RFC 3490. |
static String |
toUnicode |
Translates a string from ASCII Compatible Encoding (ACE) to Unicode, as defined by the ToUnicode operation of RFC 3490. |
static String |
toUnicode |
Translates a string from ASCII Compatible Encoding (ACE) to Unicode, as defined by the ToUnicode operation of RFC 3490. |
public static final int ALLOW_UNASSIGNED
public static final int USE_STD3_ASCII_RULES
public static String toASCII(String input, int flag)
ToASCII operation can fail. ToASCII fails if any step of it fails. If ToASCII operation fails, an IllegalArgumentException will be thrown. In this case, the input string should not be used in an internationalized domain name.
A label is an individual part of a domain name. The original ToASCII operation, as defined in RFC 3490, only operates on a single label. This method can handle both label and entire domain name, by assuming that labels in a domain name are always separated by dots. The following characters are recognized as dots: \u002E (full stop), \u3002 (ideographic full stop), \uFF0E (fullwidth full stop), and \uFF61 (halfwidth ideographic full stop). if dots are used as label separators, this method also changes all of them to \u002E (full stop) in output translated string.
input
- the string to be processedflag
- process flag; can be 0 or any logical OR of possible flagsString
IllegalArgumentException
- if the input string doesn't conform to RFC 3490 specificationpublic static String toASCII(String input)
This convenience method works as if by invoking the two-argument counterpart as follows:
toASCII
(input, 0);
input
- the string to be processedString
IllegalArgumentException
- if the input string doesn't conform to RFC 3490 specificationpublic static String toUnicode(String input, int flag)
ToUnicode never fails. In case of any error, the input string is returned unmodified.
A label is an individual part of a domain name. The original ToUnicode operation, as defined in RFC 3490, only operates on a single label. This method can handle both label and entire domain name, by assuming that labels in a domain name are always separated by dots. The following characters are recognized as dots: \u002E (full stop), \u3002 (ideographic full stop), \uFF0E (fullwidth full stop), and \uFF61 (halfwidth ideographic full stop).
input
- the string to be processedflag
- process flag; can be 0 or any logical OR of possible flagsString
public static String toUnicode(String input)
This convenience method works as if by invoking the two-argument counterpart as follows:
toUnicode
(input, 0);
input
- the string to be processedString
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https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/net/IDN.html