feat(user): ID 생성 전략 수정

src/main/java/com/goolbitg/api/service/UserServiceImpl.java

@@ -11,6 +11,7 @@
 import java.util.Random;
 
 import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.jdbc.core.JdbcTemplate;
 import org.springframework.security.oauth2.jwt.Jwt;
 import org.springframework.security.oauth2.jwt.JwtDecoder;
 import org.springframework.security.oauth2.jwt.NimbusJwtDecoder;
@@ -55,6 +56,7 @@
 import com.goolbitg.api.security.AppleLoginManager;
 import com.goolbitg.api.security.JwtManager;
 import com.goolbitg.api.util.FormatUtil;
+import com.goolbitg.api.util.RandomIdGenerator;
 
 import lombok.RequiredArgsConstructor;
 import lombok.extern.slf4j.Slf4j;
@@ -90,9 +92,7 @@ public class UserServiceImpl implements UserService {
     private final AppleLoginManager appleLoginManager;
     @Autowired
     private final TimeService timeService;
-
-    // 1 ~ 9 is reserved for default user
-    private int idSeq = 10;
+    private final JdbcTemplate jdbcTemplate;
 
 
     /* --------------- API Implements ----------------------*/
@@ -150,7 +150,7 @@ public void register(AuthRequestDto request) {
             throw UserException.alreadyRegistered(result.get().getId());
         }
 
-        String userId = String.format("id%04d", idSeq++);
+        String userId = generateId();
         User.UserBuilder userBuilder = User.builder()
                 .id(userId)
                 .registerDate(timeService.getToday());
@@ -539,4 +539,13 @@ private Long determineSpendingType(UserSurvey survey) {
         return 5L;
     }
 
+    @Transactional
+    private String generateId() {
+        String select = "SELECT * FROM `sequences` WHERE name = 'id_seq'";
+        String update = "UPDATE `sequences` SET curval = curval + 1 WHERE name = 'id_seq'";
+        int curval = jdbcTemplate.query(select, (rs, rowNum) -> rs.getInt("curval")).get(0);
+        jdbcTemplate.update(update);
+        return RandomIdGenerator.generate(curval);
+    }
+
 }

src/main/java/com/goolbitg/api/util/RandomIdGenerator.java

@@ -0,0 +1,22 @@
+package com.goolbitg.api.util;
+
+public class RandomIdGenerator {
+
+    private static final int ID_LENGTH = 10;
+
+    public static String generate(int input) {
+        StringBuilder sb;
+        String chars = "abcdefghijklmnopqrstuvwxyz";
+
+        sb = new StringBuilder();
+        int value = input;
+        for (int i = 0; i < ID_LENGTH; i++) {
+            int index = value % chars.length();
+            sb.append(chars.charAt(index));
+            value /= chars.length();
+        }
+
+        return sb.toString();
+    }
+}
+

src/main/resources/db/migrations/V5__add_id_sequence.sql

@@ -0,0 +1,8 @@
+CREATE TABLE `sequences` (
+  `name` VARCHAR(50) NOT NULL,
+  `curval` BIGINT UNSIGNED DEFAULT 0,
+  PRIMARY KEY (`name`)
+);
+
+INSERT INTO `sequences` ( `name` )
+VALUES ( 'id_seq' );

src/test/java/com/goolbitg/api/util/RandomIdGeneratorTest.java

@@ -0,0 +1,20 @@
+package com.goolbitg.api.util;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+/**
+ * RandomIdGeneratorTest
+ */
+public class RandomIdGeneratorTest {
+
+    @Test
+    void get_random_id() {
+        int src = 26;
+        String randomId = RandomIdGenerator.generate(src);
+
+        assertEquals("abaaaaaaaa", randomId);
+    }
+
+}