org.apache.juneau.http.AcceptLanguage Maven / Gradle / Ivy
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package org.apache.juneau.http;
import static org.apache.juneau.http.Constants.*;
import org.apache.juneau.internal.*;
/**
* Represents a parsed Accept-Language HTTP request header.
*
*
* List of acceptable human languages for response.
*
*
Example
*
* Accept-Language: en-US
*
*
* RFC2616 Specification
*
* The Accept-Language request-header field is similar to Accept, but restricts the set of natural languages that are
* preferred as a response to the request.
* Language tags are defined in section 3.10.
*
*
* Accept-Language = "Accept-Language" ":"
* 1#( language-range [ ";" "q" "=" qvalue ] )
* language-range = ( ( 1*8ALPHA *( "-" 1*8ALPHA ) ) | "*" )
*
*
*
* Each language-range MAY be given an associated quality value which represents an estimate of the user's preference
* for the languages specified by that range.
* The quality value defaults to "q=1".
* For example...
*
* Accept-Language: da, en-gb;q=0.8, en;q=0.7
*
*
* ...would mean: "I prefer Danish, but will accept British English and other types of English."
*
*
* A language-range matches a language-tag if it exactly equals the tag, or if it exactly equals a prefix of the tag
* such that the first tag character following the prefix is "-".
*
*
* The special range "*", if present in the Accept-Language field, matches every tag not matched by any other range
* present in the Accept-Language field.
*
*
* Note: This use of a prefix matching rule does not imply that language tags are assigned to languages in such a way
* that it is always true that if a user understands a language with a certain
* tag, then this user will also understand all languages with tags for which this tag is a prefix.
* The prefix rule simply allows the use of prefix tags if this is the case.
*
*
* The language quality factor assigned to a language-tag by the Accept-Language field is the quality value of the
* longest language- range in the field that matches the language-tag.
*
*
* If no language- range in the field matches the tag, the language quality factor assigned is 0.
*
*
* If no Accept-Language header is present in the request, the server SHOULD assume that all languages are equally
* acceptable.
*
*
* If an Accept-Language header is present, then all languages which are assigned a quality factor greater than 0 are
* acceptable.
*
*
* It might be contrary to the privacy expectations of the user to send an Accept-Language header with the complete
* linguistic preferences of the user in every request.
* For a discussion of this issue, see section 15.1.4.
*
*
* As intelligibility is highly dependent on the individual user, it is recommended that client applications make the
* choice of linguistic preference available to the user.
* If the choice is not made available, then the Accept-Language header field MUST NOT be given in the request.
*
*
* Note: When making the choice of linguistic preference available to the user, we remind implementors of the fact that
* users are not familiar with the details of language matching as described above, and should provide appropriate
* guidance.
* As an example, users might assume that on selecting "en-gb", they will be served any kind of English document if
* British English is not available.
* A user agent might suggest in such a case to add "en" to get the best matching behavior.
*
*
Additional Information
*
*/
public final class AcceptLanguage extends HeaderRangeArray {
private static final Cache cache = new Cache(NOCACHE, CACHE_MAX_SIZE);
/**
* Returns a parsed Accept-Language header.
*
* @param value The Accept-Language header string.
* @return The parsed Accept-Language header, or null if the string was null.
*/
public static AcceptLanguage forString(String value) {
if (value == null)
return null;
AcceptLanguage a = cache.get(value);
if (a == null)
a = cache.put(value, new AcceptLanguage(value));
return a;
}
private AcceptLanguage(String raw) {
super(raw);
}
}