Step1 - 레거시 코드 리팩터링

src/main/java/nextstep/qna/domain/Answer.java

@@ -1,26 +1,17 @@
 package nextstep.qna.domain;
 
+import nextstep.qna.CannotDeleteException;
 import nextstep.qna.NotFoundException;
 import nextstep.qna.UnAuthorizedException;
 import nextstep.users.domain.NsUser;
 
 import java.time.LocalDateTime;
 
-public class Answer {
-    private Long id;
-
-    private NsUser writer;
-
+public class Answer extends BaseEntity {
     private Question question;
-
+    private NsUser writer;
     private String contents;
 
-    private boolean deleted = false;
-
-    private LocalDateTime createdDate = LocalDateTime.now();
-
-    private LocalDateTime updatedDate;
-
     public Answer() {
     }
 
@@ -29,7 +20,7 @@ public Answer(NsUser writer, Question question, String contents) {
     }
 
     public Answer(Long id, NsUser writer, Question question, String contents) {
-        this.id = id;
+        super(id);
         if(writer == null) {
             throw new UnAuthorizedException();
         }
@@ -43,35 +34,32 @@ public Answer(Long id, NsUser writer, Question question, String contents) {
         this.contents = contents;
     }
 
-    public Long getId() {
-        return id;
-    }
-
-    public Answer setDeleted(boolean deleted) {
-        this.deleted = deleted;
-        return this;
-    }
-
-    public boolean isDeleted() {
-        return deleted;
+    public void delete(NsUser loginUser) throws CannotDeleteException {
+        validateDeletableBy(loginUser);
+        markAsDeleted();
     }
 
     public boolean isOwner(NsUser writer) {
         return this.writer.equals(writer);
     }
 
     public NsUser getWriter() {
-        return writer;
-    }
-
-    public String getContents() {
-        return contents;
+        return this.writer;
     }
 
     public void toQuestion(Question question) {
         this.question = question;
     }
 
+    private void validateDeletableBy(NsUser loginUser) throws CannotDeleteException {
+        if (!isOwner(loginUser)) {
+            throw new CannotDeleteException("다른 사람이 쓴 답변이 있어 삭제할 수 없습니다.");
+        }
+    }
+    public DeleteHistory createDeleteHistory() {
+        return new DeleteHistory(ContentType.ANSWER, getId(), getWriter(), LocalDateTime.now());
+    }
+
     @Override
     public String toString() {
         return "Answer [id=" + getId() + ", writer=" + writer + ", contents=" + contents + "]";

src/main/java/nextstep/qna/domain/Answers.java

@@ -0,0 +1,48 @@
+package nextstep.qna.domain;
+
+import nextstep.qna.CannotDeleteException;
+import nextstep.users.domain.NsUser;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class Answers {
+    private final List<Answer> answers;
+
+    public Answers() {
+        this(new ArrayList<>());
+    }
+
+    public Answers(Answer answer) {
+        this(List.of(answer));
+    }
+
+    public Answers(List<Answer> answers) {
+        this.answers = answers;
+    }
+
+
+    public List<Answer> getAnswers() {
+        return this.answers;
+    }
+
+    public void add(Answer answer) {
+        this.answers.add(answer);
+    }
+
+    public void delete(NsUser loginUser) throws CannotDeleteException {
+        for (Answer answer : answers) {
+            answer.delete(loginUser);
+        }
+    }
+
+    public List<DeleteHistory> createDeleteHistories() {
+        List<DeleteHistory> deleteHistories = new ArrayList<>();
+
+        for (Answer answer : answers) {
+            deleteHistories.add(answer.createDeleteHistory());
+        }
+
+        return deleteHistories;
+    }
+}

src/main/java/nextstep/qna/domain/BaseEntity.java

@@ -0,0 +1,31 @@
+package nextstep.qna.domain;
+
+import java.time.LocalDateTime;
+
+public abstract class BaseEntity {
+    private Long id;
+
+    private LocalDateTime createdDate = LocalDateTime.now();
+
+    private LocalDateTime updatedDate;
+
+    private boolean deleted = false;
+
+    public BaseEntity() {}
+
+    public BaseEntity(Long id) {
+        this.id = id;
+    }
+
+    public Long getId() {
+        return id;
+    }
+
+    protected void markAsDeleted() {
+        this.deleted = true;
+    }
+
+    public boolean isDeleted() {
+        return deleted;
+    }
+}

src/main/java/nextstep/qna/domain/PostContent.java

@@ -0,0 +1,23 @@
+package nextstep.qna.domain;
+
+import nextstep.users.domain.NsUser;
+
+public class PostContent {
+    private final NsUser writer;
+    private final String title;
+    private final String contents;
+
+    public PostContent(NsUser writer, String title, String contents) {
+        this.writer = writer;
+        this.title = title;
+        this.contents = contents;
+    }
+
+    public NsUser getWriter() {
+        return this.writer;
+    }
+
+    public boolean isOwner(NsUser loginUser) {
+        return writer.equals(loginUser);
+    }
+}

src/main/java/nextstep/qna/domain/Question.java

@@ -1,66 +1,34 @@
 package nextstep.qna.domain;
 
+import nextstep.qna.CannotDeleteException;
 import nextstep.users.domain.NsUser;
 
 import java.time.LocalDateTime;
 import java.util.ArrayList;
 import java.util.List;
 
-public class Question {
-    private Long id;
+public class Question extends BaseEntity {
+    private PostContent postContent;
 
-    private String title;
-
-    private String contents;
-
-    private NsUser writer;
-
-    private List<Answer> answers = new ArrayList<>();
-
-    private boolean deleted = false;
-
-    private LocalDateTime createdDate = LocalDateTime.now();
-
-    private LocalDateTime updatedDate;
+    private Answers answers = new Answers();
 
     public Question() {
     }
 
     public Question(NsUser writer, String title, String contents) {
-        this(0L, writer, title, contents);
+        this(0L, new PostContent(writer, title, contents));
     }
 
     public Question(Long id, NsUser writer, String title, String contents) {
-        this.id = id;
-        this.writer = writer;
-        this.title = title;
-        this.contents = contents;
-    }
-
-    public Long getId() {
-        return id;
-    }
-
-    public String getTitle() {
-        return title;
+        this(id, new PostContent(writer, title, contents));
     }
-
-    public Question setTitle(String title) {
-        this.title = title;
-        return this;
-    }
-
-    public String getContents() {
-        return contents;
-    }
-
-    public Question setContents(String contents) {
-        this.contents = contents;
-        return this;
+    public Question(Long id, PostContent postContent) {
+        super(id);
+        this.postContent = postContent;
     }
 
     public NsUser getWriter() {
-        return writer;
+        return postContent.getWriter();
     }
 
     public void addAnswer(Answer answer) {
@@ -69,24 +37,45 @@ public void addAnswer(Answer answer) {
     }
 
     public boolean isOwner(NsUser loginUser) {
-        return writer.equals(loginUser);
+        return postContent.isOwner(loginUser);
     }
 
-    public Question setDeleted(boolean deleted) {
-        this.deleted = deleted;
-        return this;
+    public void markAsDeleted(NsUser loginUser) throws CannotDeleteException {
+        validateDeletableBy(loginUser);
+        markAsDeleted();
     }
 
-    public boolean isDeleted() {
-        return deleted;
+    public void delete(NsUser loginUser) throws CannotDeleteException {
+        this.markAsDeleted(loginUser);
+        answers.delete(loginUser);
+    }
+
+    public List<DeleteHistory> createDeleteHistories() {
+        List<DeleteHistory> histories = new ArrayList<>();
+
+        histories.add(new DeleteHistory(
+                ContentType.QUESTION,
+                getId(),
+                getWriter(),
+                LocalDateTime.now()
+        ));
+
+        histories.addAll(answers.createDeleteHistories());
+
+        return histories;
     }
 
-    public List<Answer> getAnswers() {
-        return answers;
+    public void validateDeletableBy(NsUser loginUser) throws CannotDeleteException {
+        if (!isOwner(loginUser)) {
+            throw new CannotDeleteException("질문을 삭제할 권한이 없습니다.");
+        }
     }
 
     @Override
     public String toString() {
-        return "Question [id=" + getId() + ", title=" + title + ", contents=" + contents + ", writer=" + writer + "]";
+        return "Question{" +
+                "postContent=" + postContent +
+                ", answers=" + answers +
+                '}';
     }
 }

src/main/java/nextstep/qna/service/QnAService.java

@@ -8,8 +8,6 @@
 import org.springframework.transaction.annotation.Transactional;
 
 import javax.annotation.Resource;
-import java.time.LocalDateTime;
-import java.util.ArrayList;
 import java.util.List;
 
 @Service("qnaService")
@@ -26,24 +24,9 @@ public class QnAService {
     @Transactional
     public void deleteQuestion(NsUser loginUser, long questionId) throws CannotDeleteException {
         Question question = questionRepository.findById(questionId).orElseThrow(NotFoundException::new);
-        if (!question.isOwner(loginUser)) {
-            throw new CannotDeleteException("질문을 삭제할 권한이 없습니다.");
-        }
-
-        List<Answer> answers = question.getAnswers();
-        for (Answer answer : answers) {
-            if (!answer.isOwner(loginUser)) {
-                throw new CannotDeleteException("다른 사람이 쓴 답변이 있어 삭제할 수 없습니다.");
-            }
-        }
-
-        List<DeleteHistory> deleteHistories = new ArrayList<>();
-        question.setDeleted(true);
-        deleteHistories.add(new DeleteHistory(ContentType.QUESTION, questionId, question.getWriter(), LocalDateTime.now()));
-        for (Answer answer : answers) {
-            answer.setDeleted(true);
-            deleteHistories.add(new DeleteHistory(ContentType.ANSWER, answer.getId(), answer.getWriter(), LocalDateTime.now()));
-        }
-        deleteHistoryService.saveAll(deleteHistories);
+
+        question.delete(loginUser);
+
+        deleteHistoryService.saveAll(question.createDeleteHistories());
     }
-}
+}