michael@0: /*
michael@0:  * ====================================================================
michael@0:  * Licensed to the Apache Software Foundation (ASF) under one
michael@0:  * or more contributor license agreements.  See the NOTICE file
michael@0:  * distributed with this work for additional information
michael@0:  * regarding copyright ownership.  The ASF licenses this file
michael@0:  * to you under the Apache License, Version 2.0 (the
michael@0:  * "License"); you may not use this file except in compliance
michael@0:  * with the License.  You may obtain a copy of the License at
michael@0:  *
michael@0:  *   http://www.apache.org/licenses/LICENSE-2.0
michael@0:  *
michael@0:  * Unless required by applicable law or agreed to in writing,
michael@0:  * software distributed under the License is distributed on an
michael@0:  * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
michael@0:  * KIND, either express or implied.  See the License for the
michael@0:  * specific language governing permissions and limitations
michael@0:  * under the License.
michael@0:  * ====================================================================
michael@0:  *
michael@0:  * This software consists of voluntary contributions made by many
michael@0:  * individuals on behalf of the Apache Software Foundation.  For more
michael@0:  * information on the Apache Software Foundation, please see
michael@0:  * <http://www.apache.org/>.
michael@0:  *
michael@0:  */
michael@0: 
michael@0: package ch.boye.httpclientandroidlib.protocol;
michael@0: 
michael@0: import java.text.DateFormat;
michael@0: import java.text.SimpleDateFormat;
michael@0: import java.util.Date;
michael@0: import java.util.Locale;
michael@0: import java.util.TimeZone;
michael@0: 
michael@0: 
michael@0: /**
michael@0:  * Generates a date in the format required by the HTTP protocol.
michael@0:  *
michael@0:  * @since 4.0
michael@0:  */
michael@0: public class HttpDateGenerator {
michael@0: 
michael@0:     /** Date format pattern used to generate the header in RFC 1123 format. */
michael@0:     public static final
michael@0:         String PATTERN_RFC1123 = "EEE, dd MMM yyyy HH:mm:ss zzz";
michael@0: 
michael@0:     /** The time zone to use in the date header. */
michael@0:     public static final TimeZone GMT = TimeZone.getTimeZone("GMT");
michael@0: 
michael@0: 
michael@0:     private final DateFormat dateformat;
michael@0: 
michael@0:     private long dateAsLong = 0L;
michael@0:     private String dateAsText = null;
michael@0: 
michael@0:     public HttpDateGenerator() {
michael@0:         super();
michael@0:         this.dateformat = new SimpleDateFormat(PATTERN_RFC1123, Locale.US);
michael@0:         this.dateformat.setTimeZone(GMT);
michael@0:     }
michael@0: 
michael@0:     public synchronized String getCurrentDate() {
michael@0:         long now = System.currentTimeMillis();
michael@0:         if (now - this.dateAsLong > 1000) {
michael@0:             // Generate new date string
michael@0:             this.dateAsText = this.dateformat.format(new Date(now));
michael@0:             this.dateAsLong = now;
michael@0:         }
michael@0:         return this.dateAsText;
michael@0:     }
michael@0: 
michael@0: }