feat: Follow 생성, 취소 구현

Author: sapiens2000

src/main/java/com/example/log4u/domain/follow/controller/FollowController.java

@@ -0,0 +1,42 @@
+package com.example.log4u.domain.follow.controller;
+
+import org.springframework.http.ResponseEntity;
+import org.springframework.security.core.annotation.AuthenticationPrincipal;
+import org.springframework.stereotype.Controller;
+import org.springframework.web.bind.annotation.DeleteMapping;
+import org.springframework.web.bind.annotation.PathVariable;
+import org.springframework.web.bind.annotation.PostMapping;
+import org.springframework.web.bind.annotation.RequestMapping;
+
+import com.example.log4u.common.oauth2.dto.CustomOAuth2User;
+import com.example.log4u.domain.follow.service.FollowService;
+
+import io.swagger.v3.oas.annotations.tags.Tag;
+import lombok.RequiredArgsConstructor;
+
+@Tag(name = "팔로우 API")
+@Controller
+@RequiredArgsConstructor
+@RequestMapping("/users")
+public class FollowController {
+	private final FollowService followService;
+
+	@PostMapping("/{nickname}/follow")
+	public ResponseEntity<Void> createFollow(
+		@AuthenticationPrincipal CustomOAuth2User customOAuth2User,
+		@PathVariable("nickname") String nickname
+	) {
+		followService.createFollow(customOAuth2User.getUserId(), nickname);
+		return ResponseEntity.ok().build();
+	}
+
+	@DeleteMapping("/{nickname}/follow")
+	public ResponseEntity<Void> deleteFollow(
+		@AuthenticationPrincipal CustomOAuth2User customOAuth2User,
+		@PathVariable("nickname") String nickname
+	) {
+		followService.deleteFollow(customOAuth2User.getUserId(), nickname);
+		return ResponseEntity.ok().build();
+	}
+
+}

src/main/java/com/example/log4u/domain/follow/repository/FollowRepository.java

@@ -8,4 +8,6 @@
 @Repository
 public interface FollowRepository extends JpaRepository<Follow, Long> {
 	boolean existsByInitiatorIdAndTargetId(Long initiatorId, Long targetId);
+
+	void deleteByInitiatorIdAndTargetId(Long initiatorId, Long targetId);
 }

src/main/java/com/example/log4u/domain/follow/service/FollowService.java

@@ -0,0 +1,54 @@
+package com.example.log4u.domain.follow.service;
+
+import org.springframework.stereotype.Service;
+
+import com.example.log4u.domain.follow.entitiy.Follow;
+import com.example.log4u.domain.follow.exception.FollowNotFoundException;
+import com.example.log4u.domain.follow.repository.FollowRepository;
+import com.example.log4u.domain.user.service.UserService;
+
+import jakarta.transaction.Transactional;
+import lombok.RequiredArgsConstructor;
+
+@Service
+@RequiredArgsConstructor
+public class FollowService {
+	private final FollowRepository followRepository;
+	private final UserService userService;
+
+	@Transactional
+	public void createFollow(Long initiatorId, String nickname) {
+		validateTargetUser(nickname);
+		followRepository.save(Follow.of(
+			initiatorId,
+			userService.getUserIdByNickname(nickname)));
+	}
+
+	@Transactional
+	public void deleteFollow(Long userId, String nickname) {
+		Long targetId = userService.getUserIdByNickname(nickname);
+		validateFollow(userId, targetId);
+		followRepository.deleteByInitiatorIdAndTargetId(userId, targetId);
+	}
+
+	private void validateTargetUser(String nickname) {
+		// USER NOT FOUND EXCEPTION
+		userService.getUserByNickname(nickname);
+	}
+
+	private void validateFollow(Long userId, Long targetId) {
+		if (!followRepository.existsByInitiatorIdAndTargetId(userId, targetId)) {
+			throw new FollowNotFoundException();
+		}
+	}
+
+	public Long getFollowerCount() {
+		//TODO: 구현
+		return 0L;
+	}
+
+	public Long getFollowingCount() {
+		//TODO: 구현
+		return 0L;
+	}
+}