feat: Checkstyle 추가

.github/workflows/checkstyle.yml

@@ -0,0 +1,76 @@
+name: Checkstyle
+
+on:
+  pull_request:
+    branches:
+      - main
+      - develop
+  push:
+    branches:
+      - main
+      - develop
+
+jobs:
+  checkstyle:
+    name: Code Style Check
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+        with:
+          submodules: recursive
+          token: ${{ secrets.SUBMODULE_TOKEN }}
+
+      - name: Set up JDK 17
+        uses: actions/setup-java@v4
+        with:
+          java-version: '17'
+          distribution: 'temurin'
+
+      - name: Cache Gradle packages
+        uses: actions/cache@v3
+        with:
+          path: |
+            ~/.gradle/caches
+            ~/.gradle/wrapper
+          key: ${{ runner.os }}-gradle-${{ hashFiles('**/*.gradle*', '**/gradle-wrapper.properties') }}
+          restore-keys: |
+            ${{ runner.os }}-gradle-
+
+      - name: Grant execute permission for gradlew
+        run: chmod +x gradlew
+
+      - name: Run Checkstyle
+        run: ./gradlew checkstyleMain --no-daemon
+
+      - name: Upload Checkstyle Report
+        if: failure()
+        uses: actions/upload-artifact@v4
+        with:
+          name: checkstyle-report
+          path: |
+            build/reports/checkstyle/main.html
+            build/reports/checkstyle/main.xml
+          retention-days: 7
+
+      - name: Comment PR with Checkstyle Results
+        if: github.event_name == 'pull_request' && failure()
+        uses: actions/github-script@v7
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          script: |
+            const fs = require('fs');
+            const path = require('path');
+
+            let comment = '## ⚠️ Checkstyle 위반 사항 발견\n\n';
+            comment += 'Checkstyle 검사에서 코딩 컨벤션 위반이 발견되었습니다.\n\n';
+            comment += '### 📋 상세 리포트\n';
+            comment += '- [Main 소스 리포트 다운로드](../actions/runs/${{ github.run_id }})\n';
+
+            github.rest.issues.createComment({
+              issue_number: context.issue.number,
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              body: comment
+            });

build.gradle

@@ -2,6 +2,7 @@ plugins {
 	id 'java'
 	id 'org.springframework.boot' version '3.5.8'
 	id 'io.spring.dependency-management' version '1.1.7'
+	id 'checkstyle'
 }
 
 group = 'gg.agit'
@@ -64,3 +65,23 @@ clean {
 tasks.named('test') {
 	useJUnitPlatform()
 }
+
+checkstyle {
+	toolVersion = '10.12.5'
+	configFile = file("${rootDir}/config/checkstyle/checkstyle.xml")
+	configProperties = ['suppressionFile': "${rootDir}/config/checkstyle/suppressions.xml"]
+	maxWarnings = 0
+	ignoreFailures = false
+}
+
+checkstyleMain {
+	source = 'src/main/java'
+}
+
+checkstyleTest {
+	source = 'src/test/java'
+}
+
+tasks.named('build') {
+	dependsOn 'checkstyleMain'
+}

config/checkstyle/checkstyle.xml

@@ -0,0 +1,242 @@
+<?xml version="1.0"?>
+<!DOCTYPE module PUBLIC
+    "-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
+    "https://checkstyle.org/dtds/configuration_1_3.dtd">
+
+<!--
+    BCSDLab Backend Coding Convention v1.0
+    Referenced by Naver coding convention for Java (version 1.2)
+    https://naver.github.io/hackday-conventions-java/
+-->
+
+<module name="Checker">
+    <property name="charset" value="UTF-8"/>
+    <property name="severity" value="error"/>
+    <property name="fileExtensions" value="java"/>
+
+    <!-- 파일당 최대 줄 길이 -->
+    <module name="LineLength">
+        <property name="max" value="120"/>
+        <property name="ignorePattern" value="^package.*|^import.*|a href|href|http://|https://|ftp://"/>
+    </module>
+
+    <!-- 파일 끝에 새 줄 -->
+    <module name="NewlineAtEndOfFile">
+        <property name="lineSeparator" value="lf"/>
+    </module>
+
+    <!-- 탭 문자 금지 (스페이스 4칸 사용) -->
+    <module name="FileTabCharacter">
+        <property name="eachLine" value="true"/>
+    </module>
+
+    <module name="TreeWalker">
+
+        <!-- ========================================== -->
+        <!-- 1. 네이밍 규칙 -->
+        <!-- ========================================== -->
+
+        <!-- 패키지명: 소문자만 사용 -->
+        <module name="PackageName">
+            <property name="format" value="^[a-z]+(\.[a-z][a-z0-9]*)*$"/>
+            <message key="name.invalidPattern"
+                     value="패키지명 ''{0}''은 소문자만 사용해야 합니다."/>
+        </module>
+
+        <!-- 클래스/인터페이스명: PascalCase -->
+        <module name="TypeName">
+            <property name="format" value="^[A-Z][a-zA-Z0-9]*$"/>
+            <message key="name.invalidPattern"
+                     value="타입명 ''{0}''은 PascalCase를 따라야 합니다."/>
+        </module>
+
+        <!-- 메소드명: camelCase, 'check' 시작 금지 -->
+        <module name="MethodName">
+            <property name="format" value="^(?!check)[a-z][a-zA-Z0-9]*$"/>
+            <message key="name.invalidPattern"
+                     value="메소드명 ''{0}''은 camelCase를 따라야 하며, 'check'로 시작할 수 없습니다. is/has/exists/validate/require를 사용하세요."/>
+        </module>
+
+        <!-- 멤버 변수명: camelCase -->
+        <module name="MemberName">
+            <property name="format" value="^[a-z][a-zA-Z0-9]*$"/>
+            <message key="name.invalidPattern"
+                     value="멤버 변수명 ''{0}''은 camelCase를 따라야 합니다."/>
+        </module>
+
+        <!-- 파라미터명: camelCase -->
+        <module name="ParameterName">
+            <property name="format" value="^[a-z][a-zA-Z0-9]*$"/>
+            <message key="name.invalidPattern"
+                     value="파라미터명 ''{0}''은 camelCase를 따라야 합니다."/>
+        </module>
+
+        <!-- 지역 변수명: camelCase -->
+        <module name="LocalVariableName">
+            <property name="format" value="^[a-z][a-zA-Z0-9]*$"/>
+            <message key="name.invalidPattern"
+                     value="지역 변수명 ''{0}''은 camelCase를 따라야 합니다."/>
+        </module>
+
+        <!-- 상수명: UPPER_SNAKE_CASE -->
+        <module name="ConstantName">
+            <property name="format" value="^[A-Z][A-Z0-9]*(_[A-Z0-9]+)*$"/>
+            <message key="name.invalidPattern"
+                     value="상수명 ''{0}''은 UPPER_SNAKE_CASE를 따라야 합니다."/>
+        </module>
+
+        <!-- ========================================== -->
+        <!-- 2. Import 규칙 -->
+        <!-- ========================================== -->
+
+        <!-- * import 금지 -->
+        <module name="AvoidStarImport">
+            <property name="allowStaticMemberImports" value="true"/>
+        </module>
+
+        <!-- 사용하지 않는 import 금지 -->
+        <module name="UnusedImports"/>
+
+        <!-- 중복 import 금지 -->
+        <module name="RedundantImport"/>
+
+        <!-- ========================================== -->
+        <!-- 3. 코드 포맷팅 -->
+        <!-- ========================================== -->
+
+        <!-- 들여쓰기: 4칸 -->
+        <module name="Indentation">
+            <property name="basicOffset" value="4"/>
+            <property name="braceAdjustment" value="0"/>
+            <property name="caseIndent" value="4"/>
+            <property name="throwsIndent" value="4"/>
+            <property name="lineWrappingIndentation" value="4"/>
+            <property name="arrayInitIndent" value="4"/>
+        </module>
+
+        <!-- 빈 줄 관리 -->
+        <module name="EmptyLineSeparator">
+            <!-- 필드 사이에 빈 줄 없어도 허용 -->
+            <property name="allowNoEmptyLineBetweenFields" value="true"/>
+
+            <!-- 연속된 빈 줄 금지 -->
+            <property name="allowMultipleEmptyLines" value="false"/>
+            <property name="allowMultipleEmptyLinesInsideClassMembers" value="false"/>
+
+            <!-- 빈 줄 체크 대상 (VARIABLE_DEF 제외) -->
+            <property name="tokens" value="PACKAGE_DEF, IMPORT, STATIC_IMPORT,
+                                   CLASS_DEF, INTERFACE_DEF, ENUM_DEF,
+                                   STATIC_INIT, INSTANCE_INIT,
+                                   METHOD_DEF, CTOR_DEF, RECORD_DEF"/>
+        </module>
+
+        <!-- 중괄호 위치 -->
+        <module name="LeftCurly">
+            <property name="option" value="eol"/>
+        </module>
+
+        <module name="RightCurly">
+            <property name="option" value="same"/>
+        </module>
+
+        <!-- 중괄호 필수 (if, else, for, do, while) -->
+        <module name="NeedBraces">
+            <property name="allowSingleLineStatement" value="false"/>
+        </module>
+
+        <!-- 공백 규칙 -->
+        <module name="WhitespaceAround">
+            <property name="allowEmptyConstructors" value="true"/>
+            <property name="allowEmptyMethods" value="true"/>
+            <property name="allowEmptyTypes" value="true"/>
+            <property name="allowEmptyLoops" value="true"/>
+        </module>
+
+        <module name="WhitespaceAfter">
+            <property name="tokens" value="COMMA, SEMI"/>
+        </module>
+
+        <!-- Type cast 후 공백 없음 -->
+        <module name="TypecastParenPad">
+            <property name="option" value="nospace"/>
+        </module>
+
+        <module name="NoWhitespaceAfter">
+            <property name="tokens" value="TYPECAST"/>
+        </module>
+
+        <!-- 괄호 내부 공백 없음 -->
+        <module name="ParenPad">
+            <property name="option" value="nospace"/>
+        </module>
+
+        <!-- 한 줄에 하나의 statement -->
+        <module name="OneStatementPerLine"/>
+
+        <!-- 한 파일에 하나의 최상위 클래스 -->
+        <module name="OneTopLevelClass"/>
+
+        <!-- ========================================== -->
+        <!-- 4. 코딩 스타일 -->
+        <!-- ========================================== -->
+
+        <!-- 빈 블록 체크 -->
+        <module name="EmptyBlock">
+            <property name="option" value="text"/>
+        </module>
+
+        <!-- 빈 catch 블록 금지 -->
+        <module name="EmptyCatchBlock">
+            <property name="exceptionVariableName" value="expected|ignore"/>
+        </module>
+
+        <!-- 배열 선언 스타일: Java 스타일 (String[] args) -->
+        <module name="ArrayTypeStyle"/>
+
+        <!-- 긴 상수는 L 대문자 사용 -->
+        <module name="UpperEll"/>
+
+        <!-- modifier 순서 -->
+        <module name="ModifierOrder"/>
+
+        <!-- 불필요한 괄호 제거 -->
+        <module name="UnnecessaryParentheses"/>
+
+        <!-- equals() 좌변에 상수 사용 금지 (Yoda 조건 금지) -->
+        <module name="EqualsAvoidNull"/>
+
+        <!-- String 비교는 equals 사용 -->
+        <module name="StringLiteralEquality"/>
+
+        <!-- 중복 코드 체크 -->
+        <module name="SimplifyBooleanExpression"/>
+        <module name="SimplifyBooleanReturn"/>
+
+        <!-- finalize() 메소드 금지 -->
+        <module name="NoFinalizer"/>
+
+        <!-- ========================================== -->
+        <!-- 5. 어노테이션 -->
+        <!-- ========================================== -->
+
+        <!-- 어노테이션 위치 -->
+        <module name="AnnotationLocation">
+            <property name="allowSamelineMultipleAnnotations" value="false"/>
+            <property name="allowSamelineSingleParameterlessAnnotation" value="false"/>
+            <property name="allowSamelineParameterizedAnnotation" value="false"/>
+        </module>
+
+        <!-- ========================================== -->
+        <!-- 6. 기타 -->
+        <!-- ========================================== -->
+
+        <!-- 매직 넘버 금지 -->
+        <module name="MagicNumber">
+            <property name="ignoreNumbers" value="-1, 0, 1, 2"/>
+            <property name="ignoreHashCodeMethod" value="true"/>
+            <property name="ignoreAnnotation" value="true"/>
+            <property name="ignoreFieldDeclaration" value="true"/>
+        </module>
+
+    </module>
+</module>

config/checkstyle/suppressions.xml

@@ -0,0 +1,13 @@
+<?xml version="1.0"?>
+<!DOCTYPE suppressions PUBLIC
+    "-//Checkstyle//DTD SuppressionFilter Configuration 1.2//EN"
+    "https://checkstyle.org/dtds/suppressions_1_2.dtd">
+
+<suppressions>
+    <!-- QueryDSL 생성 파일 제외 -->
+    <suppress files="[\\/]generated[\\/]" checks=".*"/>
+    <suppress files="Q.*\.java" checks=".*"/>
+
+    <!-- 테스트 코드는 매직 넘버 허용 -->
+    <suppress files="[\\/]test[\\/]" checks="MagicNumber"/>
+</suppressions>

src/main/java/gg/agit/konect/domain/chat/dto/CreateChatRoomRequest.java

@@ -11,4 +11,4 @@ public record CreateChatRoomRequest(
     Integer clubId
 ) {
 
-}
+}

src/main/java/gg/agit/konect/domain/chat/model/ChatRoom.java

@@ -53,7 +53,7 @@ private ChatRoom(Integer id, User sender, User receiver) {
     }
 
     public static ChatRoom of(User sender, User receiver) {
-        return  ChatRoom.builder()
+        return ChatRoom.builder()
             .sender(sender)
             .receiver(receiver)
             .build();
@@ -84,7 +84,7 @@ public LocalDateTime getLastMessageTime() {
     }
 
     public Integer getUnreadCount(Integer userId) {
-        return (int) chatMessages.stream()
+        return (int)chatMessages.stream()
             .filter(message -> message.getReceiver().getId().equals(userId))
             .filter(message -> !message.getIsRead())
             .count();