Feat: 단축 URL로 원본 URL 조회 기능 구현

src/main/java/be/gyu/urlShortener/exception/ShortUrlNotFoundException.java

@@ -0,0 +1,6 @@
+package be.gyu.urlShortener.exception;
+
+public class ShortUrlNotFoundException extends RuntimeException{
+    public ShortUrlNotFoundException(){ super("존재하지 않는 단축 URL 입니다."); }
+    public ShortUrlNotFoundException(String msg){ super(msg); }
+}

src/main/java/be/gyu/urlShortener/repository/UrlMapRepository.java

@@ -1,9 +1,11 @@
 package be.gyu.urlShortener.repository;
 
+import java.util.Optional;
+
 import org.springframework.data.jpa.repository.JpaRepository;
 
 import be.gyu.urlShortener.entity.UrlMap;
 
 public interface UrlMapRepository extends JpaRepository<UrlMap,Integer> {
-    
+    public Optional<UrlMap> findByUrlMapShort(String urlMapShort);
 }

src/main/java/be/gyu/urlShortener/service/MainService.java

@@ -4,8 +4,10 @@ import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.stereotype.Service;
 
 import be.gyu.urlShortener.entity.UrlMap;
+import be.gyu.urlShortener.exception.ShortUrlNotFoundException;
 import be.gyu.urlShortener.repository.UrlMapRepository;
 
+import java.util.Optional;
 import java.time.LocalDateTime;
 import java.security.MessageDigest;
 import java.security.NoSuchAlgorithmException;
@@ -79,4 +81,15 @@ public class MainService {
         // 단축된 URL 반환
         return shortResult;
     }
+
+    // 단축 URL로 원본 URL 조회 및 반환 메소드
+    public String getOriginalUrl(String shortUrl){
+        Optional<UrlMap> optional=urlMapRepository.findByUrlMapShort(shortUrl);
+        
+        if(!optional.isPresent()){
+            throw new ShortUrlNotFoundException();
+        }
+
+        return optional.get().getUrlMapOriginal();
+    }
 }