1 /*
2 * Copyright 2012 The Netty Project
3 *
4 * The Netty Project licenses this file to you under the Apache License,
5 * version 2.0 (the "License"); you may not use this file except in compliance
6 * with the License. You may obtain a copy of the License at:
7 *
8 * https://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13 * License for the specific language governing permissions and limitations
14 * under the License.
15 */
16 package io.netty.util;
17
18 /**
19 * Key which can be used to access {@link Attribute} out of the {@link AttributeMap}. Be aware that it is not be
20 * possible to have multiple keys with the same name.
21 *
22 * @param <T> the type of the {@link Attribute} which can be accessed via this {@link AttributeKey}.
23 */
24 @SuppressWarnings("UnusedDeclaration") // 'T' is used only at compile time
25 public final class AttributeKey<T> extends AbstractConstant<AttributeKey<T>> {
26
27 private static final ConstantPool<AttributeKey<Object>> pool = new ConstantPool<AttributeKey<Object>>() {
28 @Override
29 protected AttributeKey<Object> newConstant(int id, String name) {
30 return new AttributeKey<Object>(id, name);
31 }
32 };
33
34 /**
35 * Returns the singleton instance of the {@link AttributeKey} which has the specified {@code name}.
36 */
37 @SuppressWarnings("unchecked")
38 public static <T> AttributeKey<T> valueOf(String name) {
39 return (AttributeKey<T>) pool.valueOf(name);
40 }
41
42 /**
43 * Returns {@code true} if a {@link AttributeKey} exists for the given {@code name}.
44 */
45 public static boolean exists(String name) {
46 return pool.exists(name);
47 }
48
49 /**
50 * Creates a new {@link AttributeKey} for the given {@code name} or fail with an
51 * {@link IllegalArgumentException} if a {@link AttributeKey} for the given {@code name} exists.
52 */
53 @SuppressWarnings("unchecked")
54 public static <T> AttributeKey<T> newInstance(String name) {
55 return (AttributeKey<T>) pool.newInstance(name);
56 }
57
58 @SuppressWarnings("unchecked")
59 public static <T> AttributeKey<T> valueOf(Class<?> firstNameComponent, String secondNameComponent) {
60 return (AttributeKey<T>) pool.valueOf(firstNameComponent, secondNameComponent);
61 }
62
63 private AttributeKey(int id, String name) {
64 super(id, name);
65 }
66 }