1 /*
2 * Copyright (c) 2015, 2018, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.net.http;
27
28 import java.util.List;
29 import java.util.Map;
30 import java.util.Optional;
31 import java.util.OptionalLong;
32 import static java.util.Collections.emptyList;
33 import static java.util.Collections.unmodifiableList;
34 import static java.util.Objects.requireNonNull;
35
36 /**
37 * A read-only view of a set of HTTP headers.
38 *
39 * <p> An {@code HttpHeaders} is not created directly, but rather returned from
40 * an {@link HttpResponse HttpResponse}. Specific HTTP headers can be set for
41 * {@linkplain HttpRequest requests} through the one of the request builder's
42 * {@link HttpRequest.Builder#header(String, String) headers} methods.
43 *
44 * <p> The methods of this class ( that accept a String header name ), and the
45 * Map returned by the {@link #map() map} method, operate without regard to
46 * case when retrieving the header value.
47 *
48 * <p> {@code HttpHeaders} instances are immutable.
49 *
50 * @since 11
51 */
52 public abstract class HttpHeaders {
53
54 /**
55 * Creates an HttpHeaders.
56 */
57 protected HttpHeaders() {}
58
59 /**
60 * Returns an {@link Optional} containing the first value of the given named
61 * (and possibly multi-valued) header. If the header is not present, then
62 * the returned {@code Optional} is empty.
63 *
64 * @implSpec
65 * The default implementation invokes
66 * {@code allValues(name).stream().findFirst()}
67 *
68 * @param name the header name
69 * @return an {@code Optional<String>} for the first named value
70 */
71 public Optional<String> firstValue(String name) {
72 return allValues(name).stream().findFirst();
73 }
74
75 /**
76 * Returns an {@link OptionalLong} containing the first value of the
77 * named header field. If the header is not present, then the Optional is
78 * empty. If the header is present but contains a value that does not parse
79 * as a {@code Long} value, then an exception is thrown.
80 *
81 * @implSpec
82 * The default implementation invokes
83 * {@code allValues(name).stream().mapToLong(Long::valueOf).findFirst()}
84 *
85 * @param name the header name
86 * @return an {@code OptionalLong}
87 * @throws NumberFormatException if a value is found, but does not parse as
88 * a Long
89 */
90 public OptionalLong firstValueAsLong(String name) {
91 return allValues(name).stream().mapToLong(Long::valueOf).findFirst();
92 }
93
94 /**
95 * Returns an unmodifiable List of all of the values of the given named
96 * header. Always returns a List, which may be empty if the header is not
97 * present.
98 *
99 * @implSpec
100 * The default implementation invokes, among other things, the
101 * {@code map().get(name)} to retrieve the list of header values.
102 *
103 * @param name the header name
104 * @return a List of String values
105 */
106 public List<String> allValues(String name) {
107 requireNonNull(name);
108 List<String> values = map().get(name);
109 // Making unmodifiable list out of empty in order to make a list which
110 // throws UOE unconditionally
111 return values != null ? values : unmodifiableList(emptyList());
112 }
113
114 /**
115 * Returns an unmodifiable multi Map view of this HttpHeaders.
116 *
117 * @return the Map
118 */
119 public abstract Map<String, List<String>> map();
120
121 /**
122 * Tests this HTTP headers instance for equality with the given object.
123 *
124 * <p> If the given object is not an {@code HttpHeaders} then this
125 * method returns {@code false}. Two HTTP headers are equal if each
126 * of their corresponding {@linkplain #map() maps} are equal.
127 *
128 * <p> This method satisfies the general contract of the {@link
129 * Object#equals(Object) Object.equals} method.
130 *
131 * @param obj the object to which this object is to be compared
132 * @return {@code true} if, and only if, the given object is an {@code
133 * HttpHeaders} that is equal to this HTTP headers
134 */
135 public final boolean equals(Object obj) {
136 if (!(obj instanceof HttpHeaders))
137 return false;
138 HttpHeaders that = (HttpHeaders)obj;
139 return this.map().equals(that.map());
140 }
141
142 /**
143 * Computes a hash code for this HTTP headers instance.
144 *
145 * <p> The hash code is based upon the components of the HTTP headers
146 * {@link #map() map}, and satisfies the general contract of the
147 * {@link Object#hashCode Object.hashCode} method.
148 *
149 * @return the hash-code value for this HTTP headers
150 */
151 public final int hashCode() {
152 return map().hashCode();
153 }
154
155 /**
156 * Returns this HTTP headers as a string.
157 *
158 * @return a string describing the HTTP headers
159 */
160 @Override
161 public String toString() {
162 StringBuilder sb = new StringBuilder();
163 sb.append(super.toString()).append(" { ");
164 sb.append(map());
165 sb.append(" }");
166 return sb.toString();
167 }
168 }