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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one
3    * or more contributor license agreements.  See the NOTICE file
4    * distributed with this work for additional information
5    * regarding copyright ownership.  The ASF licenses this file
6    * to you under the Apache License, Version 2.0 (the
7    * "License"); you may not use this file except in compliance
8    * with the License.  You may obtain a copy of the License at
9    *
10   * http://www.apache.org/licenses/LICENSE-2.0
11   *
12   * Unless required by applicable law or agreed to in writing, software
13   * distributed under the License is distributed on an "AS IS" BASIS,
14   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15   * See the License for the specific language governing permissions and
16   * limitations under the License.
17   */
18  
19  package org.apache.hadoop.hbase.util;
20  
21  import com.google.common.collect.Lists;
22  import org.apache.commons.lang.StringUtils;
23  import org.apache.hadoop.conf.Configuration;
24  import org.apache.hadoop.hbase.classification.InterfaceAudience;
25  import org.apache.hadoop.hbase.classification.InterfaceStability;
26  
27  import java.util.AbstractMap;
28  import java.util.Collection;
29  import java.util.List;
30  import java.util.Map;
31  
32  /**
33   * Utilities for storing more complex collection types in
34   * {@link org.apache.hadoop.conf.Configuration} instances.
35   */
36  @InterfaceAudience.Public
37  @InterfaceStability.Evolving
38  public final class ConfigurationUtil {
39    // TODO: hopefully this is a good delimiter; it's not in the base64 alphabet, 
40    // nor is it valid for paths
41    public static final char KVP_DELIMITER = '^';
42  
43    // Disallow instantiation
44    private ConfigurationUtil() {
45  
46    }
47  
48    /**
49     * Store a collection of Map.Entry's in conf, with each entry separated by ','
50     * and key values delimited by {@link #KVP_DELIMITER}
51     *
52     * @param conf      configuration to store the collection in
53     * @param key       overall key to store keyValues under
54     * @param keyValues kvps to be stored under key in conf
55     */
56    public static void setKeyValues(Configuration conf, String key,
57        Collection<Map.Entry<String, String>> keyValues) {
58      setKeyValues(conf, key, keyValues, KVP_DELIMITER);
59    }
60  
61    /**
62     * Store a collection of Map.Entry's in conf, with each entry separated by ','
63     * and key values delimited by delimiter.
64     *
65     * @param conf      configuration to store the collection in
66     * @param key       overall key to store keyValues under
67     * @param keyValues kvps to be stored under key in conf
68     * @param delimiter character used to separate each kvp
69     */
70    public static void setKeyValues(Configuration conf, String key,
71        Collection<Map.Entry<String, String>> keyValues, char delimiter) {
72      List<String> serializedKvps = Lists.newArrayList();
73  
74      for (Map.Entry<String, String> kvp : keyValues) {
75        serializedKvps.add(kvp.getKey() + delimiter + kvp.getValue());
76      }
77  
78      conf.setStrings(key, serializedKvps.toArray(new String[serializedKvps.size()]));
79    }
80  
81    /**
82     * Retrieve a list of key value pairs from configuration, stored under the provided key
83     *
84     * @param conf configuration to retrieve kvps from
85     * @param key  key under which the key values are stored
86     * @return the list of kvps stored under key in conf, or null if the key isn't present.
87     * @see #setKeyValues(Configuration, String, Collection, char)
88     */
89    public static List<Map.Entry<String, String>> getKeyValues(Configuration conf, String key) {
90      return getKeyValues(conf, key, KVP_DELIMITER);
91    }
92  
93    /**
94     * Retrieve a list of key value pairs from configuration, stored under the provided key
95     *
96     * @param conf      configuration to retrieve kvps from
97     * @param key       key under which the key values are stored
98     * @param delimiter character used to separate each kvp
99     * @return the list of kvps stored under key in conf, or null if the key isn't present.
100    * @see #setKeyValues(Configuration, String, Collection, char)
101    */
102   public static List<Map.Entry<String, String>> getKeyValues(Configuration conf, String key,
103       char delimiter) {
104     String[] kvps = conf.getStrings(key);
105 
106     if (kvps == null) {
107       return null;
108     }
109 
110     List<Map.Entry<String, String>> rtn = Lists.newArrayList();
111 
112     for (String kvp : kvps) {
113       String[] splitKvp = StringUtils.split(kvp, delimiter);
114 
115       if (splitKvp.length != 2) {
116         throw new IllegalArgumentException(
117             "Expected key value pair for configuration key '" + key + "'" + " to be of form '<key>"
118                 + delimiter + "<value>; was " + kvp + " instead");
119       }
120 
121       rtn.add(new AbstractMap.SimpleImmutableEntry<String, String>(splitKvp[0], splitKvp[1]));
122     }
123     return rtn;
124   }
125 }