View Javadoc

1   /**
2    * Copyright 2009 The Apache Software Foundation
3    *
4    * Licensed to the Apache Software Foundation (ASF) under one
5    * or more contributor license agreements.  See the NOTICE file
6    * distributed with this work for additional information
7    * regarding copyright ownership.  The ASF licenses this file
8    * to you under the Apache License, Version 2.0 (the
9    * "License"); you may not use this file except in compliance
10   * with the License.  You may obtain a copy of the License at
11   *
12   *     http://www.apache.org/licenses/LICENSE-2.0
13   *
14   * Unless required by applicable law or agreed to in writing, software
15   * distributed under the License is distributed on an "AS IS" BASIS,
16   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
17   * See the License for the specific language governing permissions and
18   * limitations under the License.
19   */
20  
21  package org.apache.hadoop.hbase.io;
22  
23  import java.util.*;
24  
25  /**
26   * A Static Interface.
27   * Instead of having this code in the the HbaseMapWritable code, where it
28   * blocks the possibility of altering the variables and changing their types,
29   * it is put here in this static interface where the static final Maps are
30   * loaded one time. Only byte[] and Cell are supported at this time.
31   */
32  public interface CodeToClassAndBack {
33    /**
34     * Static map that contains mapping from code to class
35     */
36    public static final Map<Byte, Class<?>> CODE_TO_CLASS =
37      new HashMap<Byte, Class<?>>();
38  
39    /**
40     * Static map that contains mapping from class to code
41     */
42    public static final Map<Class<?>, Byte> CLASS_TO_CODE =
43      new HashMap<Class<?>, Byte>();
44  
45    /**
46     * Class list for supported classes
47     */
48    public Class<?>[] classList = {byte[].class};
49  
50    /**
51     * The static loader that is used instead of the static constructor in
52     * HbaseMapWritable.
53     */
54    public InternalStaticLoader sl =
55      new InternalStaticLoader(classList, CODE_TO_CLASS, CLASS_TO_CODE);
56  
57    /**
58     * Class that loads the static maps with their values.
59     */
60    public class InternalStaticLoader{
61      InternalStaticLoader(Class<?>[] classList,
62          Map<Byte,Class<?>> CODE_TO_CLASS, Map<Class<?>, Byte> CLASS_TO_CODE){
63        byte code = 1;
64        for(int i=0; i<classList.length; i++){
65          CLASS_TO_CODE.put(classList[i], code);
66          CODE_TO_CLASS.put(code, classList[i]);
67          code++;
68        }
69      }
70    }
71  }