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1   /*
2    * Copyright 2017 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.resolver.dns;
17  
18  import java.net.InetAddress;
19  
20  /**
21   * Represents the results from a previous DNS query which can be cached.
22   */
23  public interface DnsCacheEntry {
24      /**
25       * Get the resolved address.
26       * <p>
27       * This may be null if the resolution failed, and in that case {@link #cause()} will describe the failure.
28       * @return the resolved address.
29       */
30      InetAddress address();
31  
32      /**
33       * If the DNS query failed this will provide the rational.
34       * @return the rational for why the DNS query failed, or {@code null} if the query hasn't failed.
35       */
36      Throwable cause();
37  }