Implementing Short URL Redirection with SpringBoot

Background

Short‑URL redirection converts long web links into compact URLs that are easier to share, display and track. Third‑party services typically generate a short link that redirects to the original long URL and may provide click statistics.

Significance

Space saving: Short links reduce character count for sharing.

Link beautification: They appear cleaner and more attractive.

Link stability: Short links can be updated behind the scenes to avoid broken URLs.

Analytics: Click counts, sources and regions can be tracked.

Ease of sharing: Short links copy and paste easily across platforms.

Privacy: Original URL details can be hidden.

SpringBoot Implementation

1. Database Table

A table t_url_map stores the mapping between long URLs, short URLs, the owning username and timestamps.

2. Mapping Entity

import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;
import java.time.Instant;
@Data
@Builder
@AllArgsConstructor
@NoArgsConstructor
public class UrlMap {
private Long id;
private String longUrl;
private String shortUrl;
private String username;
private Instant expireTime;
private Instant creationTime;
}

3. DAO Layer

import com.zhan.zhan215.Entity.UrlMap;
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Param;
@Mapper
public interface UrlMapMapper {
UrlMap findFirstByLongUrl(@Param("longUrl") String longUrl, @Param("username") String username);
void saveUrlMap(UrlMap urlMap);
UrlMap findByShortUrl(String shortUrl);
}

The corresponding MyBatis XML defines select and insert statements for the above methods.

4. Service Layer

import com.zhan.zhan215.Dao.UrlMapMapper;
import com.zhan.zhan215.Entity.UrlMap;
import org.springframework.stereotype.Service;
import javax.annotation.Resource;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.time.Instant;
@Service
public class UrlMapService {
@Resource
private UrlMapMapper urlMapMapper;
// Encode long URL to short URL
public String encode(String longUrl, String username) {
UrlMap urlMap = urlMapMapper.findFirstByLongUrl(longUrl, username);
if (urlMap != null && username.equals(urlMap.getUsername())) {
return urlMap.getShortUrl();
} else {
String shortLink = generateShortLink(longUrl, username);
UrlMap newMap = new UrlMap();
newMap.setLongUrl(longUrl);
newMap.setShortUrl(shortLink);
newMap.setUsername(username);
newMap.setCreationTime(Instant.now());
urlMapMapper.saveUrlMap(newMap);
return shortLink;
}
}
// Decode short URL to long URL
public String decode(String shortUrl) {
UrlMap map = urlMapMapper.findByShortUrl(shortUrl);
return map != null ? map.getLongUrl() : "https://bilibili.com";
}
// Generate short link using MD5 hash (first 8 chars) plus username
public static String generateShortLink(String originalUrl, String username) {
try {
MessageDigest md = MessageDigest.getInstance("MD5");
byte[] hash = md.digest(originalUrl.getBytes());
StringBuilder sb = new StringBuilder();
for (byte b : hash) { sb.append(String.format("%02x", b)); }
return sb.toString().substring(0, 8) + username;
} catch (NoSuchAlgorithmException e) { e.printStackTrace(); return null; }
}
}

5. Controller Layer

import com.zhan.zhan215.Common.ResponseBean;
import com.zhan.zhan215.Service.UrlMapService;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.servlet.view.RedirectView;
import javax.annotation.Resource;
@RestController
public class UrlMapController {
@Resource
private UrlMapService urlMapService;
@PostMapping("/shorten")
    public ResponseBean shorten(@RequestParam String longUrl, @RequestParam String username) {
String short = urlMapService.encode(longUrl, username);
return ResponseBean.success(short);
}
@GetMapping("redirect")
    public RedirectView redirectView(@RequestParam String shortUrl) {
String longUrl = urlMapService.decode(shortUrl);
return new RedirectView(longUrl);
}
}

6. Response Wrapper

public class ResponseBean
{
private boolean success;
private T data;
// getters and setters omitted for brevity
public static
ResponseBean
success(T data) {
ResponseBean
r = new ResponseBean<>();
r.setSuccess(true); r.setData(data); return r;
}
public static
ResponseBean
error(T errorData) {
ResponseBean
r = new ResponseBean<>();
r.setSuccess(false); r.setData(errorData); return r;
}
}

Result Testing

A sample Bilibili video URL is shortened to a value such as 1b9590bezhan . Accessing the short link correctly redirects to the original long URL, confirming the implementation works.

Discussion

The username parameter is included so that different users generating a short link for the same long URL receive distinct short URLs, enabling per‑user tracking and analytics.