001// ***************************************************************************************************************************
002// * Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements.  See the NOTICE file *
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006// *                                                                                                                         *
007// *  http://www.apache.org/licenses/LICENSE-2.0                                                                             *
008// *                                                                                                                         *
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010// * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the License for the        *
011// * specific language governing permissions and limitations under the License.                                              *
012// ***************************************************************************************************************************
013package org.apache.juneau.http.header;
014
015import java.util.function.*;
016
017import org.apache.juneau.http.*;
018import org.apache.juneau.http.annotation.*;
019
020/**
021 * Represents a parsed <l>If-Range</l> HTTP request header.
022 *
023 * <p>
024 * If the entity is unchanged, send me the part(s) that I am missing; otherwise, send me the entire new entity.
025 *
026 * <h5 class='figure'>Example</h5>
027 * <p class='bcode w800'>
028 *    If-Range: "737060cd8c284d8af7ad3082f209582d"
029 * </p>
030 *
031 * <h5 class='topic'>RFC2616 Specification</h5>
032 *
033 * If a client has a partial copy of an entity in its cache, and wishes to have an up-to-date copy of the entire entity
034 * in its cache, it could use the Range request-header with a conditional GET (using either or both of
035 * If-Unmodified-Since and If-Match.)
036 * However, if the condition fails because the entity has been modified, the client would then have to make a second
037 * request to obtain the entire current entity-body.
038 *
039 * <p>
040 * The If-Range header allows a client to "short-circuit" the second request.
041 * Informally, its meaning is `if the entity is unchanged, send me the part(s) that I am missing; otherwise, send me
042 * the entire new entity'.
043 * <p class='bcode w800'>
044 *    If-Range = "If-Range" ":" ( entity-tag | HTTP-date )
045 * </p>
046 *
047 * <p>
048 * If the client has no entity tag for an entity, but does have a Last- Modified date, it MAY use that date in an
049 * If-Range header.
050 * (The server can distinguish between a valid HTTP-date and any form of entity-tag by examining no more than two
051 * characters.)
052 * The If-Range header SHOULD only be used together with a Range header, and MUST be ignored if the request does not
053 * include a Range header, or if the server does not support the sub-range operation.
054 *
055 * <p>
056 * If the entity tag given in the If-Range header matches the current entity tag for the entity, then the server SHOULD
057 * provide the specified sub-range of the entity using a 206 (Partial content) response.
058 * If the entity tag does not match, then the server SHOULD return the entire entity using a 200 (OK) response.
059 *
060 * <ul class='seealso'>
061 *    <li class='extlink'>{@doc ExtRFC2616}
062 * </ul>
063 */
064@Header("If-Range")
065public class IfRange extends BasicDateHeader {
066
067   private static final long serialVersionUID = 1L;
068
069   private final Object value;  // Only set if value is an entity tag.
070
071   /**
072    * Convenience creator.
073    *
074    * @param value
075    *    The header value.
076    *    <br>Can be any of the following:
077    *    <ul>
078    *       <li>{@link String}
079    *       <li>Anything else - Converted to <c>String</c> then parsed.
080    *    </ul>
081    * @return A new {@link IfRange} object.
082    */
083   public static IfRange of(Object value) {
084      if (value == null)
085         return null;
086      return new IfRange(value);
087   }
088
089   /**
090    * Convenience creator using supplier.
091    *
092    * <p>
093    * Header value is re-evaluated on each call to {@link #getValue()}.
094    *
095    * @param value
096    *    The header value supplier.
097    *    <br>Can be any of the following:
098    *    <ul>
099    *       <li>{@link String}
100    *       <li>Anything else - Converted to <c>String</c> then parsed.
101    *    </ul>
102    * @return A new {@link IfRange} object.
103    */
104   public static IfRange of(Supplier<?> value) {
105      if (value == null)
106         return null;
107      return new IfRange(value);
108   }
109
110   /**
111    * Constructor.
112    *
113    * @param value
114    *    The header value.
115    *    <br>Can be any of the following:
116    *    <ul>
117    *       <li>{@link String}
118    *       <li>Anything else - Converted to <c>String</c> then parsed.
119    *       <li>A {@link Supplier} of anything on this list.
120    *    </ul>
121    */
122   public IfRange(Object value) {
123      super("If-Range", dateValue(value));
124      this.value = etagValue(value);
125   }
126
127   /**
128    * Constructor
129    *
130    * @param value
131    *    The header value.
132    */
133   public IfRange(String value) {
134      this((Object)value);
135   }
136
137   private static Object dateValue(Object o) {
138      Object o2 = unwrap(o);
139      if (o2 == null || isEtag(o2))
140         return null;
141      return o;
142   }
143
144   private static Object etagValue(Object o) {
145      Object o2 = unwrap(o);
146      if (o2 == null || isEtag(o2))
147         return o;
148      return null;
149   }
150
151   private static boolean isEtag(Object o) {
152      String s = o.toString();
153      return s.startsWith("\"") || s.startsWith("W/");
154   }
155
156   @Override /* Header */
157   public String getValue() {
158      if (value == null)
159         return super.getValue();
160      Object o = unwrap(value);
161      return (o == null ? null : o.toString());
162   }
163
164   /**
165    * Returns this header as an {@link EntityTag}.
166    *
167    * @return This header as an {@link EntityTag}.
168    */
169   public EntityTag asEntityTag() {
170      return (value == null ? null : EntityTag.of(value));
171   }
172}