短域名服务设计与实现

红太狼 2023-06-26 05:37 15阅读 0赞

### 1、设计方案 ###

两步走：

1）长域名转短域名并存储

使用redis，使用固定key和redis自增函数获取累计自增数值，加上固定前缀作为key，将长域名值作为value，存储至redis。

2）短域名解析与跳转长域名

使用过滤器filter，拦截所有请求，根据命名规则过滤短域名url，并做对应长域名的转换，最终完成跳转。

### 2、长域名转短域名并存储 ###

import com.ddyunf.cloud.base.service.url.ShortUrlService;
    import org.apache.commons.codec.digest.DigestUtils;
    import org.slf4j.Logger;
    import org.slf4j.LoggerFactory;
    import org.springframework.beans.factory.annotation.Value;
    import org.springframework.data.redis.core.StringRedisTemplate;
    import org.springframework.data.redis.core.ValueOperations;
    import org.springframework.stereotype.Service;
    
    import javax.annotation.Resource;
    import java.util.concurrent.TimeUnit;
    
    /**
     * Created by kou on 2017/11/27.
     */
    @Service("defaultShortUrlService")
    public class DefaultShortUrlServiceImpl implements ShortUrlService{
    
        private static final Logger log = LoggerFactory.getLogger(DefaultShortUrlServiceImpl.class);
    
        @Value("${short.url.prefix}")
        private String shortUrlPrefix;
        @Value("${short.url.timeout}")
        private Long shortUrlTimeout;
    
    
        @Resource
        private StringRedisTemplate stringRedisTemplate;
    
        private static final  String KeyPrefix = "short_url_hash_md5_key_";
    
        private static final  String shortUrlKeyPrefix = "short_url_hash_key_";
    
        private static final  String serialNumberKey = "short_url_serial_number";
    
        final static char[] digits = { '0', '1', '2', '3', '4', '5', '6', '7', '8',
                'z', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L',
                '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',
                'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y',
                'Z', '-', '_'};
    
        @Override
        public String transformUrl(String url) {
    
            ValueOperations<String, String> operations = stringRedisTemplate.opsForValue();
    
            final String md5 = DigestUtils.md5Hex(url);
            String shortUrl = operations.get(KeyPrefix + md5);
            if (shortUrl == null){
                synchronized (md5.intern()){
                    shortUrl = operations.get(KeyPrefix + md5);
                    if (shortUrl == null){
                        Long value = stringRedisTemplate.opsForValue().increment(serialNumberKey, 1);
                        String longString = compressNumber(value);
                        shortUrl = shortUrlPrefix + longString;
                        operations.set(KeyPrefix + md5, shortUrl, shortUrlTimeout, TimeUnit.DAYS);
                        operations.set(shortUrlKeyPrefix + longString, url, shortUrlTimeout, TimeUnit.DAYS);
                    }
                }
            }
            return shortUrl;
        }
    
        public String findOriginalUrl(String shortUrl) {
            ValueOperations<String, String> operations = stringRedisTemplate.opsForValue();
            return operations.get(shortUrlKeyPrefix + shortUrl);
        }
    
        private static String compressNumber(long number) {
            char[] buf = new char[64];
            int charPos = 64;
            int radix = 1 << 6;
            long mask = radix - 1;
            do {
                buf[--charPos] = digits[(int) (number & mask)];
                number >>>= 6;
            } while (number != 0);
            return new String(buf, charPos, (64 - charPos));
        }
    }

### 3、短域名过滤与跳转至长域名 ###

import org.apache.commons.lang3.StringUtils;
    import org.slf4j.Logger;
    import org.slf4j.LoggerFactory;
    import org.springframework.data.redis.core.StringRedisTemplate;
    import org.springframework.web.context.WebApplicationContext;
    import org.springframework.web.context.support.WebApplicationContextUtils;
    import org.springframework.web.filter.OncePerRequestFilter;
    
    import javax.servlet.FilterChain;
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.io.IOException;
    import java.io.PrintWriter;
    
    public class ShortUrlFilter extends OncePerRequestFilter {
    
    	private static final String SHORT_URL_PREFIX = "/t/";
    
    	private static final  String SHORT_URL_KEY_PREFIX = "short_url_hash_key_";
    
    	private static final Logger log = LoggerFactory.getLogger(ShortUrlFilter.class);
    
    	private StringRedisTemplate stringRedisTemplate;
    
    	@Override
    	protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException {
    		String uri = request.getRequestURI();
    		String contextPath = request.getContextPath();
    		String url = uri.substring(contextPath.length());
    
    		if(!url.startsWith(SHORT_URL_PREFIX)) {
    			filterChain.doFilter(request, response);
    			return;
    		}
    
    		if (stringRedisTemplate == null){
    			WebApplicationContext ac = WebApplicationContextUtils.getWebApplicationContext(
    					request.getSession().getServletContext());
    			stringRedisTemplate = (StringRedisTemplate) ac.getBean("stringRedisTemplate");
    		}
    
    		String longUrl = stringRedisTemplate.opsForValue().get(SHORT_URL_KEY_PREFIX + url.substring(url.lastIndexOf("/") + 1));
    
    		if (StringUtils.isBlank(longUrl)){
    			log.warn("对应url {},没有找到原链接", url);
    			response.setCharacterEncoding("UTF-8");
    			response.setContentType("application/json");
    			PrintWriter out = response.getWriter();
    			out.write("{\"flag\":\"error\",\"msg\":\"抱歉，原链接已过期销毁\",\"data\":null}");
    			out.flush();
    			return;
    		}
    
    		response.setCharacterEncoding("UTF-8");
    		response.setContentType("text/html");
    		PrintWriter out = response.getWriter();
    		out.write("<!DOCTYPE html>\n" +
    				"<html lang=\"en\">\n" +
    				"<head>\n" +
    				"    <meta charset=\"UTF-8\">\n" +
    				"    <title>Title</title>\n" +
    				"</head>\n" +
    				"<body>\n" +
    				"<script>\n" +
    				"    window.location.href = '"+ longUrl +"'" +
    				"</script>\n" +
    				"\n" +
    				"</body>\n" +
    				"</html>");
    		out.flush();
    	}
    }

### 4、web.xml ###

<filter>
    		<filter-name>urlFilter</filter-name>
    		<filter-class>***.ShortUrlFilter</filter-class>
    	</filter>
    	<filter-mapping>
    		<filter-name>urlFilter</filter-name>
    		<url-pattern>/t/*</url-pattern>
    	</filter-mapping>