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/*
* ValueParser.java September 2003
*
* Copyright (C) 2003, Niall Gallagher
*
* 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;
/**
* The ValueParser is used to extract a comma separated
* list of HTTP header values. This will extract values without
* any leading or trailing spaces, which enables the values to be
* used. Listing the values that appear in the header also requires
* that the values are ordered. This orders the values using the
* values that appear with any quality parameter associated with it.
* The quality value is a special parameter that often found in a
* comma separated value list to specify the client preference.
*
*
* image/gif, image/jpeg, text/html
* image/gif;q=1.0, image/jpeg;q=0.8, image/png; q=1.0,*;q=0.1
* gzip;q=1.0, identity; q=0.5, *;q=0
*
*
* The above lists taken from RFC 2616 provides an example of the
* common form comma separated values take. The first illustrates
* a simple comma delimited list, here the ordering of values is
* determined from left to right. The second and third list have
* quality values associated with them, these are used to specify
* a preference and thus order.
*
* Each value within a list has an implicit quality value of 1.0.
* If the value is explicitly set with a the "q" parameter, then
* the values can range from 1.0 to 0.001. This parser ensures
* that the order of values returned from the list
* method adheres to the optional quality parameters and ensures
* that the quality parameters a removed from the resulting text.
*
* @author Niall Gallagher
*/
public class ValueParser extends ListParser {
/**
* Constructor for the ValueParser. This creates
* a parser with no initial parse data, if there are headers to
* be parsed then the parse(String) method or
* parse(List) method can be used. This will
* parse a delimited list according so RFC 2616 section 4.2.
*/
public ValueParser(){
super();
}
/**
* Constructor for the ValueParser. This creates
* a parser with the text supplied. This will parse the comma
* separated list according to RFC 2616 section 2.1 and 4.2.
* The tokens can be extracted using the list
* method, which will also sort and trim the tokens.
*
* @param text this is the comma separated list to be parsed
*/
public ValueParser(String text) {
super(text);
}
/**
* Constructor for the ValueParser. This creates
* a parser with the text supplied. This will parse the comma
* separated list according to RFC 2616 section 2.1 and 4.2.
* The tokens can be extracted using the list
* method, which will also sort and trim the tokens.
*
* @param list a list of comma separated lists to be parsed
*/
public ValueParser(List list) {
super(list);
}
/**
* This creates a string object using an offset and a length.
* The string is created from the extracted token and the offset
* and length ensure that no leading or trailing whitespace are
* within the created string object.
*
* @param text this is the text buffer to acquire the value from
* @param start the offset within the buffer to take characters
* @param len this is the number of characters within the token
*/
@Override
protected String create(char[] text, int start, int len){
return new String(text, start, len);
}
}