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1   /**
2    *
3    * Licensed to the Apache Software Foundation (ASF) under one
4    * or more contributor license agreements.  See the NOTICE file
5    * distributed with this work for additional information
6    * regarding copyright ownership.  The ASF licenses this file
7    * to you under the Apache License, Version 2.0 (the
8    * "License"); you may not use this file except in compliance
9    * with the License.  You may obtain a copy of the License at
10   *
11   *     http://www.apache.org/licenses/LICENSE-2.0
12   *
13   * Unless required by applicable law or agreed to in writing, software
14   * distributed under the License is distributed on an "AS IS" BASIS,
15   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16   * See the License for the specific language governing permissions and
17   * limitations under the License.
18   */
19  package org.apache.hadoop.hbase.util;
20  
21  import java.util.StringTokenizer;
22  import java.util.regex.Matcher;
23  import java.util.regex.Pattern;
24  
25  import org.apache.hadoop.classification.InterfaceAudience;
26  import org.apache.hadoop.classification.InterfaceStability;
27  
28  /**
29   * Utility creating hbase friendly keys.
30   * Use fabricating row names or column qualifiers.
31   * <p>TODO: Add createSchemeless key, a key that doesn't care if scheme is
32   * http or https.
33   * @see Bytes#split(byte[], byte[], int)
34   */
35  @InterfaceAudience.Public
36  @InterfaceStability.Stable
37  public class Keying {
38    private static final String SCHEME = "r:";
39    private static final Pattern URI_RE_PARSER =
40      Pattern.compile("^([^:/?#]+://(?:[^/?#@]+@)?)([^:/?#]+)(.*)$");
41  
42    /**
43     * Makes a key out of passed URI for use as row name or column qualifier.
44     *
45     * This method runs transforms on the passed URI so it sits better
46     * as a key (or portion-of-a-key) in hbase.  The <code>host</code> portion of
47     * the URI authority is reversed so subdomains sort under their parent
48     * domain.  The returned String is an opaque URI of an artificial
49     * <code>r:</code> scheme to prevent the result being considered an URI of
50     * the original scheme.  Here is an example of the transform: The url
51     * <code>http://lucene.apache.org/index.html?query=something#middle<code> is
52     * returned as
53     * <code>r:http://org.apache.lucene/index.html?query=something#middle</code>
54     * The transforms are reversible.  No transform is done if passed URI is
55     * not hierarchical.
56     *
57     * <p>If authority <code>userinfo</code> is present, will mess up the sort
58     * (until we do more work).</p>
59     *
60     * @param u URL to transform.
61     * @return An opaque URI of artificial 'r' scheme with host portion of URI
62     * authority reversed (if present).
63     * @see #keyToUri(String)
64     * @see <a href="http://www.ietf.org/rfc/rfc2396.txt">RFC2396</a>
65     */
66    public static String createKey(final String u) {
67      if (u.startsWith(SCHEME)) {
68        throw new IllegalArgumentException("Starts with " + SCHEME);
69      }
70      Matcher m = getMatcher(u);
71      if (m == null || !m.matches()) {
72        // If no match, return original String.
73        return u;
74      }
75      return SCHEME + m.group(1) + reverseHostname(m.group(2)) + m.group(3);
76    }
77  
78    /**
79     * Reverse the {@link #createKey(String)} transform.
80     *
81     * @param s <code>URI</code> made by {@link #createKey(String)}.
82     * @return 'Restored' URI made by reversing the {@link #createKey(String)}
83     * transform.
84     */
85    public static String keyToUri(final String s) {
86      if (!s.startsWith(SCHEME)) {
87        return s;
88      }
89      Matcher m = getMatcher(s.substring(SCHEME.length()));
90      if (m == null || !m.matches()) {
91        // If no match, return original String.
92        return s;
93      }
94      return m.group(1) + reverseHostname(m.group(2)) + m.group(3);
95    }
96  
97    private static Matcher getMatcher(final String u) {
98      if (u == null || u.length() <= 0) {
99        return null;
100     }
101     return URI_RE_PARSER.matcher(u);
102   }
103 
104   private static String reverseHostname(final String hostname) {
105     if (hostname == null) {
106       return "";
107     }
108     StringBuilder sb = new StringBuilder(hostname.length());
109     for (StringTokenizer st = new StringTokenizer(hostname, ".", false);
110         st.hasMoreElements();) {
111       Object next = st.nextElement();
112       if (sb.length() > 0) {
113         sb.insert(0, ".");
114       }
115       sb.insert(0, next);
116     }
117     return sb.toString();
118   }
119 
120 }