1 /*
2 * Copyright 2011 Király Attila
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://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,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16 package com.github.cage.token;
17
18 import java.util.Random;
19
20 import com.github.cage.IGenerator;
21 import com.github.cage.IGeneratorFactory;
22
23 /**
24 * A simple random String generator that can be used to generate tokens for the
25 * captcha images.
26 *
27 * In its default mode instances of this class generate words from English lower
28 * cased letters where vowels and consonants are alternating.
29 *
30 * @author akiraly
31 */
32 public class RandomTokenGenerator implements IGenerator<String> {
33
34 /**
35 * Default minimum length of token.
36 */
37 protected static final int DEFAULT_TOKEN_LEN_MIN = 8;
38
39 /**
40 * Default maximum length of token is {@link #DEFAULT_TOKEN_LEN_MIN} +
41 * {@value #DEFAULT_TOKEN_LEN_DELTA}.
42 */
43 protected static final int DEFAULT_TOKEN_LEN_DELTA = 2;
44
45 private final IGeneratorFactory<Character> characterGeneratorFactory;
46 private final int minLength;
47 private final int delta;
48 private final Random rnd;
49
50 /**
51 * Constructor.
52 */
53 public RandomTokenGenerator() {
54 this(null);
55 }
56
57 /**
58 * Constructor.
59 *
60 * @param rnd
61 * random generator to be used, can be null
62 */
63 public RandomTokenGenerator(Random rnd) {
64 this(rnd, DEFAULT_TOKEN_LEN_MIN, DEFAULT_TOKEN_LEN_DELTA);
65 }
66
67 /**
68 * Constructor.
69 *
70 * @param length
71 * the length of the generated words, must be > 0
72 * @param rnd
73 * random generator to be used, can be null
74 */
75 public RandomTokenGenerator(Random rnd, int length) {
76 this(rnd, length, 0);
77 }
78
79 /**
80 * Constructor.
81 *
82 * @param rnd
83 * random generator to be used, can be null
84 * @param minLength
85 * the minimum length of the generated words, must be > 0
86 * @param delta
87 * minLength + delta is the maximum length of the generated
88 * words, delta must be >= 0
89 */
90 public RandomTokenGenerator(Random rnd, int minLength, int delta) {
91 this(rnd, new RandomCharacterGeneratorFactory(rnd != null ? rnd
92 : new Random()), minLength, delta);
93 }
94
95 /**
96 * Constructor.
97 *
98 * @param rnd
99 * random generator to be used, can be null
100 * @param characterGeneratorFactory
101 * character generator factory to be used for the actual
102 * character creation, can be null
103 * @param minLength
104 * the minimum length of the generated words, must be > 0
105 * @param delta
106 * minLength + delta is the maximum length of the generated
107 * words, delta must be >= 0
108 */
109 public RandomTokenGenerator(Random rnd,
110 IGeneratorFactory<Character> characterGeneratorFactory,
111 int minLength, int delta) {
112 this.characterGeneratorFactory = characterGeneratorFactory != null ? characterGeneratorFactory
113 : new RandomCharacterGeneratorFactory();
114 this.minLength = Math.abs(minLength);
115 this.delta = Math.abs(delta);
116 this.rnd = rnd != null ? rnd : new Random();
117 }
118
119 public String next() {
120 int length = (delta <= 1 ? 0 : rnd.nextInt(delta) + 1) + minLength;
121 char[] word = new char[length];
122 IGenerator<Character> generator = characterGeneratorFactory.next();
123
124 for (int fi = 0; fi < word.length; fi++) {
125 word[fi] = generator.next();
126 }
127
128 return new String(word);
129 }
130
131 /**
132 * @return character generator factory used by this class, not null
133 */
134 public IGeneratorFactory<Character> getCharacterGeneratorFactory() {
135 return characterGeneratorFactory;
136 }
137
138 /**
139 * @return minimum length of generated tokens
140 */
141 public int getMinLength() {
142 return minLength;
143 }
144
145 /**
146 * @return maximum length difference to add to the minimum length
147 */
148 public int getDelta() {
149 return delta;
150 }
151 }