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Hutool是一个小而全的Java工具类库，通过静态方法封装，降低相关API的学习成本，提高工作效率，使Java拥有函数式语言般的优雅，让Java语言也可以“甜甜的”。
package cn.hutool.core.codec;
import java.math.BigInteger;
import java.util.Arrays;
import java.util.LinkedHashSet;
import java.util.Map;
import java.util.Objects;
import java.util.Set;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
import java.util.stream.LongStream;
/**
* Hashids 协议实现，以实现：
*
* - 生成简短、唯一、大小写敏感并无序的hash值
* - 自然数字的Hash值
* - 可以设置不同的盐，具有保密性
* - 可配置的hash长度
* - 递增的输入产生的输出无法预测
*
*
*
* 来自：https://github.com/davidafsilva/java-hashids
*
*
*
* {@code Hashids}可以将数字或者16进制字符串转为短且唯一不连续的字符串，采用双向编码实现，比如，它可以将347之类的数字转换为yr8之类的字符串，也可以将yr8之类的字符串重新解码为347之类的数字。
* 此编码算法主要是解决爬虫类应用对连续ID爬取问题，将有序的ID转换为无序的Hashids，而且一一对应。
*
*
* @author david
*/
public class Hashids implements Encoder, Decoder {
private static final int LOTTERY_MOD = 100;
private static final double GUARD_THRESHOLD = 12;
private static final double SEPARATOR_THRESHOLD = 3.5;
// 最小编解码字符串
private static final int MIN_ALPHABET_LENGTH = 16;
private static final Pattern HEX_VALUES_PATTERN = Pattern.compile("[\\w\\W]{1,12}");
// 默认编解码字符串
public static final char[] DEFAULT_ALPHABET = {
'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
'1', '2', '3', '4', '5', '6', '7', '8', '9', '0'
};
// 默认分隔符
private static final char[] DEFAULT_SEPARATORS = {
'c', 'f', 'h', 'i', 's', 't', 'u', 'C', 'F', 'H', 'I', 'S', 'T', 'U'
};
// algorithm properties
private final char[] alphabet;
// 多个数字编解码的分界符
private final char[] separators;
private final Set separatorsSet;
private final char[] salt;
// 补齐至 minLength 长度添加的字符列表
private final char[] guards;
// 编码后最小的字符长度
private final int minLength;
// region create
/**
* 根据参数值，创建{@code Hashids}，使用默认{@link #DEFAULT_ALPHABET}作为字母表，不限制最小长度
*
* @param salt 加盐值
* @return {@code Hashids}
*/
public static Hashids create(final char[] salt) {
return create(salt, DEFAULT_ALPHABET, -1);
}
/**
* 根据参数值，创建{@code Hashids}，使用默认{@link #DEFAULT_ALPHABET}作为字母表
*
* @param salt 加盐值
* @param minLength 限制最小长度，-1表示不限制
* @return {@code Hashids}
*/
public static Hashids create(final char[] salt, final int minLength) {
return create(salt, DEFAULT_ALPHABET, minLength);
}
/**
* 根据参数值，创建{@code Hashids}
*
* @param salt 加盐值
* @param alphabet hash字母表
* @param minLength 限制最小长度，-1表示不限制
* @return {@code Hashids}
*/
public static Hashids create(final char[] salt, final char[] alphabet, final int minLength) {
return new Hashids(salt, alphabet, minLength);
}
// endregion
/**
* 构造
*
* @param salt 加盐值
* @param alphabet hash字母表
* @param minLength 限制最小长度，-1表示不限制
*/
public Hashids(final char[] salt, final char[] alphabet, final int minLength) {
this.minLength = minLength;
this.salt = Arrays.copyOf(salt, salt.length);
// filter and shuffle separators
char[] tmpSeparators = shuffle(filterSeparators(DEFAULT_SEPARATORS, alphabet), this.salt);
// validate and filter the alphabet
char[] tmpAlphabet = validateAndFilterAlphabet(alphabet, tmpSeparators);
// check separator threshold
if (tmpSeparators.length == 0 ||
((double) (tmpAlphabet.length / tmpSeparators.length)) > SEPARATOR_THRESHOLD) {
final int minSeparatorsSize = (int) Math.ceil(tmpAlphabet.length / SEPARATOR_THRESHOLD);
// check minimum size of separators
if (minSeparatorsSize > tmpSeparators.length) {
// fill separators from alphabet
final int missingSeparators = minSeparatorsSize - tmpSeparators.length;
tmpSeparators = Arrays.copyOf(tmpSeparators, tmpSeparators.length + missingSeparators);
System.arraycopy(tmpAlphabet, 0, tmpSeparators,
tmpSeparators.length - missingSeparators, missingSeparators);
System.arraycopy(tmpAlphabet, 0, tmpSeparators,
tmpSeparators.length - missingSeparators, missingSeparators);
tmpAlphabet = Arrays.copyOfRange(tmpAlphabet, missingSeparators, tmpAlphabet.length);
}
}
// shuffle the current alphabet
shuffle(tmpAlphabet, this.salt);
// check guards
this.guards = new char[(int) Math.ceil(tmpAlphabet.length / GUARD_THRESHOLD)];
if (alphabet.length < 3) {
System.arraycopy(tmpSeparators, 0, guards, 0, guards.length);
this.separators = Arrays.copyOfRange(tmpSeparators, guards.length, tmpSeparators.length);
this.alphabet = tmpAlphabet;
} else {
System.arraycopy(tmpAlphabet, 0, guards, 0, guards.length);
this.separators = tmpSeparators;
this.alphabet = Arrays.copyOfRange(tmpAlphabet, guards.length, tmpAlphabet.length);
}
// create the separators set
separatorsSet = IntStream.range(0, separators.length)
.mapToObj(idx -> separators[idx])
.collect(Collectors.toSet());
}
/**
* 编码给定的16进制数字
*
* @param hexNumbers 16进制数字
* @return 编码后的值, {@code null} if {@code numbers} 是 {@code null}.
* @throws IllegalArgumentException 数字不支持抛出此异常
*/
public String encodeFromHex(final String hexNumbers) {
if (hexNumbers == null) {
return null;
}
// remove the prefix, if present
final String hex = hexNumbers.startsWith("0x") || hexNumbers.startsWith("0X") ?
hexNumbers.substring(2) : hexNumbers;
// get the associated long value and encode it
LongStream values = LongStream.empty();
final Matcher matcher = HEX_VALUES_PATTERN.matcher(hex);
while (matcher.find()) {
final long value = new BigInteger("1" + matcher.group(), 16).longValue();
values = LongStream.concat(values, LongStream.of(value));
}
return encode(values.toArray());
}
/**
* 编码给定的数字数组
*
* @param numbers 数字数组
* @return 编码后的值, {@code null} if {@code numbers} 是 {@code null}.
* @throws IllegalArgumentException 数字不支持抛出此异常
*/
@Override
public String encode(final long... numbers) {
if (numbers == null) {
return null;
}
// copy alphabet
final char[] currentAlphabet = Arrays.copyOf(alphabet, alphabet.length);
// determine the lottery number
final long lotteryId = LongStream.range(0, numbers.length)
.reduce(0, (state, i) -> {
final long number = numbers[(int) i];
if (number < 0) {
throw new IllegalArgumentException("invalid number: " + number);
}
return state + number % (i + LOTTERY_MOD);
});
final char lottery = currentAlphabet[(int) (lotteryId % currentAlphabet.length)];
// encode each number
final StringBuilder global = new StringBuilder();
IntStream.range(0, numbers.length)
.forEach(idx -> {
// derive alphabet
deriveNewAlphabet(currentAlphabet, salt, lottery);
// encode
final int initialLength = global.length();
translate(numbers[idx], currentAlphabet, global, initialLength);
// prepend the lottery
if (idx == 0) {
global.insert(0, lottery);
}
// append the separator, if more numbers are pending encoding
if (idx + 1 < numbers.length) {
long n = numbers[idx] % (global.charAt(initialLength) + 1);
global.append(separators[(int) (n % separators.length)]);
}
});
// add the guards, if there's any space left
if (minLength > global.length()) {
int guardIdx = (int) ((lotteryId + lottery) % guards.length);
global.insert(0, guards[guardIdx]);
if (minLength > global.length()) {
guardIdx = (int) ((lotteryId + global.charAt(2)) % guards.length);
global.append(guards[guardIdx]);
}
}
// add the necessary padding
int paddingLeft = minLength - global.length();
while (paddingLeft > 0) {
shuffle(currentAlphabet, Arrays.copyOf(currentAlphabet, currentAlphabet.length));
final int alphabetHalfSize = currentAlphabet.length / 2;
final int initialSize = global.length();
if (paddingLeft > currentAlphabet.length) {
// entire alphabet with the current encoding in the middle of it
int offset = alphabetHalfSize + (currentAlphabet.length % 2 == 0 ? 0 : 1);
global.insert(0, currentAlphabet, alphabetHalfSize, offset);
global.insert(offset + initialSize, currentAlphabet, 0, alphabetHalfSize);
// decrease the padding left
paddingLeft -= currentAlphabet.length;
} else {
// calculate the excess
final int excess = currentAlphabet.length + global.length() - minLength;
final int secondHalfStartOffset = alphabetHalfSize + Math.floorDiv(excess, 2);
final int secondHalfLength = currentAlphabet.length - secondHalfStartOffset;
final int firstHalfLength = paddingLeft - secondHalfLength;
global.insert(0, currentAlphabet, secondHalfStartOffset, secondHalfLength);
global.insert(secondHalfLength + initialSize, currentAlphabet, 0, firstHalfLength);
paddingLeft = 0;
}
}
return global.toString();
}
//-------------------------
// Decode
//-------------------------
/**
* 解码Hash值为16进制数字
*
* @param hash hash值
* @return 解码后的16进制值, {@code null} if {@code numbers} 是 {@code null}.
* @throws IllegalArgumentException if the hash is invalid.
*/
public String decodeToHex(final String hash) {
if (hash == null) {
return null;
}
final StringBuilder sb = new StringBuilder();
Arrays.stream(decode(hash))
.mapToObj(Long::toHexString)
.forEach(hex -> sb.append(hex, 1, hex.length()));
return sb.toString();
}
/**
* 解码Hash值为数字数组
*
* @param hash hash值
* @return 解码后的16进制值, {@code null} if {@code numbers} 是 {@code null}.
* @throws IllegalArgumentException if the hash is invalid.
*/
@Override
public long[] decode(final String hash) {
if (hash == null) {
return null;
}
// create a set of the guards
final Set guardsSet = IntStream.range(0, guards.length)
.mapToObj(idx -> guards[idx])
.collect(Collectors.toSet());
// count the total guards used
final int[] guardsIdx = IntStream.range(0, hash.length())
.filter(idx -> guardsSet.contains(hash.charAt(idx)))
.toArray();
// get the start/end index base on the guards count
final int startIdx, endIdx;
if (guardsIdx.length > 0) {
startIdx = guardsIdx[0] + 1;
endIdx = guardsIdx.length > 1 ? guardsIdx[1] : hash.length();
} else {
startIdx = 0;
endIdx = hash.length();
}
LongStream decoded = LongStream.empty();
// parse the hash
if (hash.length() > 0) {
final char lottery = hash.charAt(startIdx);
// create the initial accumulation string
final int length = hash.length() - guardsIdx.length - 1;
StringBuilder block = new StringBuilder(length);
// create the base salt
final char[] decodeSalt = new char[alphabet.length];
decodeSalt[0] = lottery;
final int saltLength = salt.length >= alphabet.length ? alphabet.length - 1 : salt.length;
System.arraycopy(salt, 0, decodeSalt, 1, saltLength);
final int saltLeft = alphabet.length - saltLength - 1;
// copy alphabet
final char[] currentAlphabet = Arrays.copyOf(alphabet, alphabet.length);
for (int i = startIdx + 1; i < endIdx; i++) {
if (false == separatorsSet.contains(hash.charAt(i))) {
block.append(hash.charAt(i));
// continue if we have not reached the end, yet
if (i < endIdx - 1) {
continue;
}
}
if (block.length() > 0) {
// create the salt
if (saltLeft > 0) {
System.arraycopy(currentAlphabet, 0, decodeSalt,
alphabet.length - saltLeft, saltLeft);
}
// shuffle the alphabet
shuffle(currentAlphabet, decodeSalt);
// prepend the decoded value
final long n = translate(block.toString().toCharArray(), currentAlphabet);
decoded = LongStream.concat(decoded, LongStream.of(n));
// create a new block
block = new StringBuilder(length);
}
}
}
// validate the hash
final long[] decodedValue = decoded.toArray();
if (!Objects.equals(hash, encode(decodedValue))) {
throw new IllegalArgumentException("invalid hash: " + hash);
}
return decodedValue;
}
private StringBuilder translate(final long n, final char[] alphabet,
final StringBuilder sb, final int start) {
long input = n;
do {
// prepend the chosen char
sb.insert(start, alphabet[(int) (input % alphabet.length)]);
// trim the input
input = input / alphabet.length;
} while (input > 0);
return sb;
}
private long translate(final char[] hash, final char[] alphabet) {
long number = 0;
final Map alphabetMapping = IntStream.range(0, alphabet.length)
.mapToObj(idx -> new Object[]{alphabet[idx], idx})
.collect(Collectors.groupingBy(arr -> (Character) arr[0],
Collectors.mapping(arr -> (Integer) arr[1],
Collectors.reducing(null, (a, b) -> a == null ? b : a))));
for (int i = 0; i < hash.length; ++i) {
number += alphabetMapping.computeIfAbsent(hash[i], k -> {
throw new IllegalArgumentException("Invalid alphabet for hash");
}) * (long) Math.pow(alphabet.length, hash.length - i - 1);
}
return number;
}
private char[] deriveNewAlphabet(final char[] alphabet, final char[] salt, final char lottery) {
// create the new salt
final char[] newSalt = new char[alphabet.length];
// 1. lottery
newSalt[0] = lottery;
int spaceLeft = newSalt.length - 1;
int offset = 1;
// 2. salt
if (salt.length > 0 && spaceLeft > 0) {
int length = Math.min(salt.length, spaceLeft);
System.arraycopy(salt, 0, newSalt, offset, length);
spaceLeft -= length;
offset += length;
}
// 3. alphabet
if (spaceLeft > 0) {
System.arraycopy(alphabet, 0, newSalt, offset, spaceLeft);
}
// shuffle
return shuffle(alphabet, newSalt);
}
private char[] validateAndFilterAlphabet(final char[] alphabet, final char[] separators) {
// validate size
if (alphabet.length < MIN_ALPHABET_LENGTH) {
throw new IllegalArgumentException(String.format("alphabet must contain at least %d unique " +
"characters: %d", MIN_ALPHABET_LENGTH, alphabet.length));
}
final Set seen = new LinkedHashSet<>(alphabet.length);
final Set invalid = IntStream.range(0, separators.length)
.mapToObj(idx -> separators[idx])
.collect(Collectors.toSet());
// add to seen set (without duplicates)
IntStream.range(0, alphabet.length)
.forEach(i -> {
if (alphabet[i] == ' ') {
throw new IllegalArgumentException(String.format("alphabet must not contain spaces: " +
"index %d", i));
}
final Character c = alphabet[i];
if (!invalid.contains(c)) {
seen.add(c);
}
});
// create a new alphabet without the duplicates
final char[] uniqueAlphabet = new char[seen.size()];
int idx = 0;
for (char c : seen) {
uniqueAlphabet[idx++] = c;
}
return uniqueAlphabet;
}
@SuppressWarnings("SameParameterValue")
private char[] filterSeparators(final char[] separators, final char[] alphabet) {
final Set valid = IntStream.range(0, alphabet.length)
.mapToObj(idx -> alphabet[idx])
.collect(Collectors.toSet());
return IntStream.range(0, separators.length)
.mapToObj(idx -> (separators[idx]))
.filter(valid::contains)
// ugly way to convert back to char[]
.map(c -> Character.toString(c))
.collect(Collectors.joining())
.toCharArray();
}
private char[] shuffle(final char[] alphabet, final char[] salt) {
for (int i = alphabet.length - 1, v = 0, p = 0, j, z; salt.length > 0 && i > 0; i--, v++) {
v %= salt.length;
p += z = salt[v];
j = (z + v + p) % i;
final char tmp = alphabet[j];
alphabet[j] = alphabet[i];
alphabet[i] = tmp;
}
return alphabet;
}
}
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