阿里二面：如何設計與實現(xiàn)短URL服務？

package util;

import redis.clients.jedis.Jedis;

/**
?* Created by pfliu on 2019/06/23.
?*/
public?class?ShortURLUtil?{


????private?static?final String SHORT_URL_KEY = "SHORT_URL_KEY";
????private?static?final String LOCALHOST = "http://localhost:4444/";
????private?static?final String SHORT_LONG_PREFIX = "short_long_prefix_";
????private?static?final String CACHE_KEY_PREFIX = "cache_key_prefix_";
????private?static?final int?CACHE_SECONDS = 1?* 60?* 60;

????private?final String redisConfig;
????private?final Jedis jedis;

????public?ShortURLUtil(String redisConfig) {
????????this.redisConfig = redisConfig;
????????this.jedis = new?Jedis(this.redisConfig);
????}

????public?String getShortURL(String longURL, Decimal decimal) {
????????// 查詢緩存
????????String cache = jedis.get(CACHE_KEY_PREFIX + longURL);
????????if?(cache != null) {
????????????return?LOCALHOST + toOtherBaseString(Long.valueOf(cache), decimal.x);
????????}

????????// 自增
????????long?num = jedis.incr(SHORT_URL_KEY);
????????// 在數(shù)據(jù)庫中保存短-長URL的映射關系,可以保存在MySQL中
????????jedis.set(SHORT_LONG_PREFIX + num, longURL);
????????// 寫入緩存
????????jedis.setex(CACHE_KEY_PREFIX + longURL, CACHE_SECONDS, String.valueOf(num));
????????return?LOCALHOST + toOtherBaseString(num, decimal.x);
????}

????/**
?????* 在進制表示中的字符集合
?????*/
????final static?char[] digits = {'0', '1', '2', '3', '4', '5', '6', '7', '8',
????????????'9', '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'};

????/**
?????* 由10進制的數(shù)字轉(zhuǎn)換到其他進制
?????*/
????private?String toOtherBaseString(long?n, int?base) {
????????long?num = 0;
????????if?(n < 0) {
????????????num = ((long) 2?* 0x7fffffff) + n + 2;
????????} else?{
????????????num = n;
????????}
????????char[] buf = new?char[32];
????????int?charPos = 32;
????????while?((num / base) > 0) {
????????????buf[--charPos] = digits[(int) (num % base)];
????????????num /= base;
????????}
????????buf[--charPos] = digits[(int) (num % base)];
????????return?new?String(buf, charPos, (32?- charPos));
????}

????enum?Decimal {
????????D32(32),
????????D64(64);

????????int?x;

????????Decimal(int?x) {
????????????this.x = x;
????????}
????}


????public?static?void?main(String[] args) {

????????for?(int?i = 0; i < 100; i++) {
????????????System.out.println(new?ShortURLUtil("localhost").getShortURL("www.baidudu.com", Decimal.D32));
????????????System.out.println(new?ShortURLUtil("localhost").getShortURL("www.baidu.com", Decimal.D64));
????????}
????}
}

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