001    /**
002     *  Licensed to the Apache Software Foundation (ASF) under one or more
003     *  contributor license agreements.  See the NOTICE file distributed with
004     *  this work for additional information regarding copyright ownership.
005     *  The ASF licenses this file to You under the Apache License, Version 2.0
006     *  (the "License"); you may not use this file except in compliance with
007     *  the License.  You may obtain a copy of the License at
008     *
009     *     http://www.apache.org/licenses/LICENSE-2.0
010     *
011     *  Unless required by applicable law or agreed to in writing, software
012     *  distributed under the License is distributed on an "AS IS" BASIS,
013     *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     *  See the License for the specific language governing permissions and
015     *  limitations under the License.
016     */
017    
018    package org.apache.xbean.osgi.bundle.util;
019    
020    import java.util.List;
021    import java.util.Map;
022    import java.util.regex.Pattern;
023    
024    import org.apache.xbean.osgi.bundle.util.HeaderParser.HeaderElement;
025    
026    /**
027     * @version $Rev: 1160977 $ $Date: 2011-08-24 13:02:21 +0800 (Wed, 24 Aug 2011) $
028     */
029    public class HeaderBuilder {
030    
031        private static final Pattern EXTENDED_PATTERN = Pattern.compile("[\\w_\\-\\.]+");
032    
033        public static String build(List<HeaderElement> headerElements) {
034            if (headerElements == null || headerElements.size() == 0) {
035                return "";
036            }
037            StringBuilder header = new StringBuilder();
038            for (HeaderElement headerElement : headerElements) {
039                String name = headerElement.getName();
040                if (name == null || name.length() == 0) {
041                    throw new IllegalArgumentException("Invalid header name for the header elment " + headerElement);
042                }
043                if (header.length() > 0) {
044                    header.append(",");
045                }
046                header.append(name);
047                for (Map.Entry<String, String> attribute : headerElement.getAttributes().entrySet()) {
048                    header.append(";").append(attribute.getKey()).append("=");
049                    if (EXTENDED_PATTERN.matcher(attribute.getValue()).matches()) {
050                        header.append(attribute.getValue());
051                    } else {
052                        header.append("\"").append(attribute.getValue()).append("\"");
053                    }
054                }
055                for (Map.Entry<String, String> directive : headerElement.getDirectives().entrySet()) {
056                    header.append(";").append(directive.getKey()).append(":=");
057                    if (EXTENDED_PATTERN.matcher(directive.getValue()).matches()) {
058                        header.append(directive.getValue());
059                    } else {
060                        header.append("\"").append(directive.getValue()).append("\"");
061                    }
062                }
063            }
064            return header.toString();
065        }
066    }