댓글 api 추가

src/main/java/com/community/dev/domain/reply/Reply.java

@@ -0,0 +1,36 @@
+package com.community.dev.domain.reply;
+
+import com.community.dev.domain.post.Post;
+import lombok.Getter;
+import lombok.Setter;
+
+import javax.persistence.*;
+
+@Getter
+@Entity
+public class Reply {
+
+    @Setter
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Long id;
+
+
+    @ManyToOne
+    private Post post;
+
+    private String writer;
+    private String contents;
+
+    protected Reply() {}
+
+    public Reply(Post post, String writer, String contents) {
+        this.post = post;
+        this.writer = writer;
+        this.contents = contents;
+    }
+
+    public static Reply createReply(Post post, String writer, String contents) {
+        return new Reply(post, writer, contents);
+    }
+}

src/main/java/com/community/dev/domain/reply/ReplyRepo.java

@@ -0,0 +1,9 @@
+package com.community.dev.domain.reply;
+
+import org.springframework.data.jpa.repository.JpaRepository;
+
+import java.util.List;
+
+public interface ReplyRepo extends JpaRepository<Reply, Long> {
+    List<Reply> findByPostId(long postId);
+}

src/main/java/com/community/dev/service/reply/ReplyService.java

@@ -0,0 +1,29 @@
+package com.community.dev.service.reply;
+
+import com.community.dev.domain.reply.Reply;
+import com.community.dev.domain.reply.ReplyRepo;
+import com.community.dev.service.post.PostService;
+import org.springframework.stereotype.Service;
+
+import java.util.List;
+
+@Service
+public class ReplyService {
+
+    private final ReplyRepo replyRepo;
+    private final PostService postService;
+
+    public ReplyService(ReplyRepo replyRepo, PostService postService) {
+        this.replyRepo = replyRepo;
+        this.postService = postService;
+    }
+
+    public void createReply(Long postId, Reply reply) {
+        postService.getPost(postId);
+        replyRepo.save(Reply.createReply(postService.exist(postId), reply.getWriter(), reply.getContents()));
+    }
+
+    public List<Reply> getReplies(long id) {
+        return replyRepo.findByPostId(id);
+    }
+}

src/main/java/com/community/dev/web/PostController.java

@@ -2,6 +2,7 @@
 
 import com.community.dev.domain.post.Post;
 import com.community.dev.service.post.PostService;
+import com.community.dev.service.reply.ReplyService;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.stereotype.Controller;
 import org.springframework.ui.Model;
@@ -17,10 +18,12 @@
 public class PostController {
 
     private final PostService postService;
+    private final ReplyService replyService;
 
     @Autowired
-    public PostController(PostService postService) {
+    public PostController(PostService postService, ReplyService replyService) {
         this.postService = postService;
+        this.replyService = replyService;
     }
 
     @GetMapping("write")
@@ -46,6 +49,7 @@ public String writePost(@Valid Post post, BindingResult result, Model model) {
     @GetMapping("/{id}")
     public String showDetailForm(@PathVariable("id") long id, Model model) {
         model.addAttribute("post", postService.getPost(id));
+        model.addAttribute("reply", replyService.getReplies(id));
         return "post-detail";
     }
 

src/main/java/com/community/dev/web/ReplyController.java

@@ -0,0 +1,41 @@
+package com.community.dev.web;
+
+import com.community.dev.domain.reply.Reply;
+import com.community.dev.service.post.PostService;
+import com.community.dev.service.reply.ReplyService;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Controller;
+import org.springframework.ui.Model;
+import org.springframework.validation.BindingResult;
+import org.springframework.web.bind.annotation.PathVariable;
+import org.springframework.web.bind.annotation.PostMapping;
+import org.springframework.web.bind.annotation.RequestMapping;
+
+import javax.validation.Valid;
+
+@Controller
+@RequestMapping("/{id}/replies/")
+public class ReplyController {
+
+    private final PostService postService;
+    private final ReplyService replyService;
+
+    @Autowired
+    public ReplyController(PostService postService, ReplyService replyService) {
+        this.postService = postService;
+        this.replyService = replyService;
+    }
+
+
+    @PostMapping("/write")
+    public String writeReply(@PathVariable("id") long id, @Valid Reply reply, BindingResult result, Model model) {
+        if (result.hasErrors()) {
+            return "reply-add";
+        }
+        replyService.createReply(id, reply);
+
+        model.addAttribute("post", postService.getPost(id));
+        model.addAttribute("reply", replyService.getReplies(id));
+        return "post-detail";
+    }
+}

src/test/java/com/community/dev/domain/reply/ReplyRepoTest.java

@@ -0,0 +1,44 @@
+package com.community.dev.domain.reply;
+
+import com.community.dev.domain.post.Post;
+import com.community.dev.domain.post.PostRepo;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.jdbc.AutoConfigureTestDatabase;
+import org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTest;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+@AutoConfigureTestDatabase(replace = AutoConfigureTestDatabase.Replace.NONE)
+@DataJpaTest
+class ReplyRepoTest {
+
+    private Post post;
+
+    @Autowired
+    private ReplyRepo replyRepo;
+
+    @Autowired
+    private PostRepo postRepo;
+
+    @BeforeEach
+    void setUp() {
+        post = Post.createPost("writer", "title,", "contents", "1234");
+
+        postRepo.save(post);
+        replyRepo.save(Reply.createReply(post, "replyWriter", "replyContents"));
+        replyRepo.save(Reply.createReply(post, "replyWriter2", "replyContents2"));
+    }
+
+    @Test
+    void 댓글_저장() {
+        Reply reply = Reply.createReply(this.post, "replyWriter3", "replyContents3");
+        assertThat(replyRepo.save(reply).getContents()).isEqualTo("replyContents3");
+    }
+
+    @Test
+    void 하나의_게시글에_작성된_댓글_개수_조회() {
+        assertThat(replyRepo.findByPostId(post.getId()).size()).isEqualTo(2);
+    }
+}