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/*
* LanguageParser.java February 2001
*
* Copyright (C) 2001, Niall Gallagher <niallg@users.sf.net>
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
* implied. See the License for the specific language governing
* permissions and limitations under the License.
*/
package org.simpleframework.http.parse;
import java.util.List;
import java.util.Locale;
/**
* LanguageParser is used to parse the HTTP <code>Accept-Language</code>
* header. This takes in an <code>Accept-Language</code> header and parses
* it according the RFC 2616 BNF for the <code>Accept-Language</code> header.
* This also has the ability to sequence the language tokens in terms of
* the most preferred and the least preferred.
* <p>
* This uses the qvalues outlined by RFC 2616 to order the language tokens
* by preference. Typically the language tokens will not have qvalues with
* the language. However when a language tag has the qvalue parameter then
* this tag will be ordered based on the value of that parameter. A language
* tag without the qvalue parameter is considered to have a qvalue of 1 and
* is ordered accordingly.
*
* @author Niall Gallagher
*/
public class LanguageParser extends ListParser<Locale> {
/**
* This is used to create a <code>LanguageParser</code> for the
* <code>Accept-Language</code> HTTP header value. This will
* parse a set of language tokens and there parameters. The
* languages will be ordered on preference. This constructor
* will parse the value given using <code>parse(String)</code>.
*/
public LanguageParser() {
super();
}
/**
* This is used to create a <code>LanguageParser</code> for the
* <code>Accept-Language</code> HTTP header value. This will
* parse a set of language tokens and there parameters. The
* languages will be ordered on preference. This constructor
* will parse the value given using <code>parse(String)</code>.
*
* @param text value of a <code>Accept-Language</code> header
*/
public LanguageParser(String text) {
super(text);
}
/**
* This is used to create a <code>LanguageParser</code> for the
* <code>Accept-Language</code> HTTP header value. This will
* parse a set of language tokens and there parameters. The
* languages will be ordered on preference. This constructor
* will parse the value given using <code>parse(String)</code>.
*
* @param list value of a <code>Accept-Language</code> header
*/
public LanguageParser(List<String> list) {
super(list);
}
/**
* This creates a locale object using an offset and a length.
* The locale is created from the extracted token and the offset
* and length ensure that no leading or trailing whitespace are
* within the created locale object.
*
* @param text this is the text buffer to acquire the value from
* @param start the offset within the array to take characters
* @param len this is the number of characters within the token
*/
@Override
protected Locale create(char[] text, int start, int len){
String language = language(text, start, len);
String country = country(text, start, len);
return new Locale(language, country);
}
/**
* This will extract the primary language tag from the header.
* This token is used to represent the language that will be
* available in the <code>Locale</code> object created.
*
* @param text this is the text buffer to acquire the value from
* @param start the offset within the array to take characters
* @param len this is the number of characters within the token
*/
private String language(char[] text, int start, int len) {
int mark = start;
int size = 0;
while(start < len) {
char next = text[start];
if(terminal(next)) {
return new String(text, mark, size);
}
size++;
start++;
}
return new String(text, mark, len);
}
/**
* This will extract the primary country tag from the header.
* This token is used to represent the country that will be
* available in the <code>Locale</code> object created.
*
* @param text this is the text buffer to acquire the value from
* @param start the offset within the array to take characters
* @param len this is the number of characters within the token
*/
private String country(char[] text, int start, int len) {
int size = len;
while(start < len) {
if(text[start++] == '-') {
return new String(text, start, --size);
}
size--;
}
return "";
}
/**
* This is used to determine whether the character provided is
* a terminal character. The terminal token is the value that is
* used to separate the country from the language and also any
* character the marks the end of the language token.
*
* @param ch this is the character that is to be evaluated
*
* @return true if the character represents a terminal token
*/
private boolean terminal(char ch) {
return ch ==' ' || ch == '-' || ch == ';';
}
}
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