[feat] 채팅방 관련 기능 구현

be/src/main/java/kr/codesquad/secondhand/api/chat/controller/ChatRoomController.java

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+package kr.codesquad.secondhand.api.chat.controller;
+
+import static kr.codesquad.secondhand.global.util.HttpAuthorizationUtils.extractMemberId;
+
+import javax.servlet.http.HttpServletRequest;
+import kr.codesquad.secondhand.api.chat.dto.ChatRoomCreateDto;
+import kr.codesquad.secondhand.api.chat.service.ChatFacadeService;
+import lombok.RequiredArgsConstructor;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.ResponseEntity;
+import org.springframework.validation.annotation.Validated;
+import org.springframework.web.bind.annotation.PostMapping;
+import org.springframework.web.bind.annotation.RequestBody;
+import org.springframework.web.bind.annotation.RestController;
+
+@RestController
+@RequiredArgsConstructor
+public class ChatRoomController {
+
+    private final ChatFacadeService chatService;
+
+    @PostMapping("/api/chat/room")
+    public ResponseEntity<ChatRoomCreateDto.Response> createChatRoom(HttpServletRequest httpServletRequest,
+                                                                     @Validated @RequestBody ChatRoomCreateDto.Request request) {
+        Long memberId = extractMemberId(httpServletRequest);
+        ChatRoomCreateDto.Response response = chatService.createChatRoom(memberId, request.getProductId());
+        return ResponseEntity
+                .status(HttpStatus.CREATED)
+                .body(response);
+    }
+}

be/src/main/java/kr/codesquad/secondhand/api/chat/domain/ChatRoom.java

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+package kr.codesquad.secondhand.api.chat.domain;
+
+import java.util.UUID;
+import javax.persistence.Entity;
+import javax.persistence.FetchType;
+import javax.persistence.Id;
+import javax.persistence.JoinColumn;
+import javax.persistence.ManyToOne;
+import kr.codesquad.secondhand.api.member.domain.Member;
+import kr.codesquad.secondhand.api.product.domain.Product;
+import lombok.AccessLevel;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+
+@Entity
+@Getter
+@NoArgsConstructor(access = AccessLevel.PROTECTED)
+public class ChatRoom {
+
+    @Id
+    private String id;
+
+    @ManyToOne(fetch = FetchType.LAZY)
+    @JoinColumn(name = "product_id")
+    private Product product;
+
+    @ManyToOne(fetch = FetchType.LAZY)
+    @JoinColumn(name = "member_id")
+    private Member member;
+
+    private ChatRoom(String id, Product product, Member member) {
+        this.id = id;
+        this.product = product;
+        this.member = member;
+    }
+
+    public static ChatRoom create(Product product, Member member) {
+        String id = UUID.randomUUID().toString();
+        return new ChatRoom(id, product, member);
+    }
+}

be/src/main/java/kr/codesquad/secondhand/api/chat/dto/ChatRoomCreateDto.java

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+package kr.codesquad.secondhand.api.chat.dto;
+
+import javax.validation.Valid;
+import javax.validation.constraints.NotBlank;
+import javax.validation.constraints.NotNull;
+import lombok.Getter;
+
+public class ChatRoomCreateDto {
+
+    @Getter
+    public static class Request {
+
+        @NotNull(message = "생성할 채팅방의 상품 정보가 비어있습니다.")
+        private Long productId;
+
+        @Valid
+        private MessageDTO message;
+    }
+
+    @Getter
+    private static class MessageDTO {
+
+        @NotNull(message = "생성할 채팅방의 senderId가 비어있습니다.")
+        private Long senderId;
+
+        @NotBlank(message = "생성할 채팅방의 메시지 내용이 없습니다.")
+        private String content;
+    }
+
+    @Getter
+    public static class Response {
+
+        private final String roomId;
+
+        public Response(String roomId) {
+            this.roomId = roomId;
+        }
+    }
+}

be/src/main/java/kr/codesquad/secondhand/api/chat/repository/ChatRoomRepositoryImpl.java

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+package kr.codesquad.secondhand.api.chat.repository;
+
+import kr.codesquad.secondhand.api.chat.domain.ChatRoom;
+import org.springframework.data.jpa.repository.JpaRepository;
+
+public interface ChatRoomRepositoryImpl extends JpaRepository<ChatRoom, String> {
+}

be/src/main/java/kr/codesquad/secondhand/api/chat/service/ChatFacadeService.java

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+package kr.codesquad.secondhand.api.chat.service;
+
+import kr.codesquad.secondhand.api.chat.domain.ChatRoom;
+import kr.codesquad.secondhand.api.chat.dto.ChatRoomCreateDto;
+import kr.codesquad.secondhand.api.member.domain.Member;
+import kr.codesquad.secondhand.api.member.service.MemberService;
+import kr.codesquad.secondhand.api.product.domain.Product;
+import kr.codesquad.secondhand.api.product.service.ProductService;
+import lombok.RequiredArgsConstructor;
+import org.springframework.stereotype.Service;
+
+@Service
+@RequiredArgsConstructor
+public class ChatFacadeService {
+
+    private final ChatService chatService;
+    private final ProductService productService;
+    private final MemberService memberService;
+
+    public ChatRoomCreateDto.Response createChatRoom(Long memberId, Long productId) {
+        Member member = memberService.getMemberReferenceById(memberId); // 없는 경우에 무슨 예외 터지는지 확인
+        Product product = productService.findById(productId);
+        ChatRoom chatRoom = chatService.createChatRoom(product, member);
+
+        // TODO request의 첫 메시지 관련 처리 필요
+        return new ChatRoomCreateDto.Response(chatRoom.getId());
+    }
+
+}

be/src/main/java/kr/codesquad/secondhand/api/chat/service/ChatService.java

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+package kr.codesquad.secondhand.api.chat.service;
+
+import kr.codesquad.secondhand.api.chat.domain.ChatRoom;
+import kr.codesquad.secondhand.api.chat.repository.ChatRoomRepositoryImpl;
+import kr.codesquad.secondhand.api.member.domain.Member;
+import kr.codesquad.secondhand.api.product.domain.Product;
+import lombok.RequiredArgsConstructor;
+import org.springframework.stereotype.Service;
+
+@Service
+@RequiredArgsConstructor
+public class ChatService {
+
+    private final ChatRoomRepositoryImpl chatRoomRepository;
+
+    public ChatRoom createChatRoom(Product product, Member member) {
+        ChatRoom chatRoom = ChatRoom.create(product, member);
+        chatRoomRepository.save(chatRoom);
+        return chatRoom;
+    }
+
+}