diff --git a/.gitignore b/.gitignore
new file mode 100644
index 00000000..bdce78c8
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,83 @@
+HELP.md
+.gradle
+build/
+!gradle/wrapper/gradle-wrapper.jar
+!**/src/main/**/build/
+!**/src/test/**/build/
+application.yml
+
+### STS ###
+.apt_generated
+.classpath
+.factorypath
+.project
+.settings
+.springBeans
+.sts4-cache
+bin/
+!**/src/main/**/bin/
+!**/src/test/**/bin/
+
+### IntelliJ IDEA ###
+.idea
+*.iws
+*.iml
+*.ipr
+out/
+!**/src/main/**/out/
+!**/src/test/**/out/
+
+### NetBeans ###
+/nbproject/private/
+/nbbuild/
+/dist/
+/nbdist/
+/.nb-gradle/
+
+### VS Code ###
+.vscode/
+
+*#
+*.iml
+*.ipr
+*.iws
+*.jar
+*.sw?
+*~
+.#*
+.*.md.html
+.DS_Store
+.attach_pid*
+.classpath
+.factorypath
+.gradle
+.metadata
+.project
+.recommenders
+.settings
+.springBeans
+.vscode
+/code
+MANIFEST.MF
+_site/
+activemq-data
+bin
+build
+!/**/src/**/bin
+!/**/src/**/build
+build.log
+dependency-reduced-pom.xml
+dump.rdb
+interpolated*.xml
+lib/
+manifest.yml
+out
+overridedb.*
+target
+.flattened-pom.xml
+secrets.yml
+.gradletasknamecache
+.sts4-cache
+
+.idea
+.env
diff --git a/README.md b/README.md
index a394e048..787950b5 100644
--- a/README.md
+++ b/README.md
@@ -1,2 +1,151 @@
-# spring-instagram-20th
-CEOS 20th BE study - instagram clone coding
+## 1. 데이터베이스 모델링
+
+## pre. 요구사항 분석
+
+**[인스타그램 서비스 분석]**
+
+### 1. 서비스 개요
+
+인스타그램은 사용자들이 게시글을 작성하고, 댓글을 달며, 좋아요를 누르고, 메시지를 주고받을 수 있는 기능을 제공합니다.
+
+### 2. 기능 요구사항
+
+### 2.1 게시글 기능
+
+- **게시글 조회**: 사용자는 타인의 게시글을 조회할 수 있습니다.
+- **게시글 작성**: 사용자는 텍스트와 사진을 포함하여 게시글을 작성할 수 있습니다.
+- **게시글 수정 및 삭제**: 사용자는 자신이 작성한 게시글을 수정하거나 삭제할 수 있습니다.
+
+### 2.2 댓글 기능
+
+- **댓글 작성**: 사용자는 게시글에 댓글을 작성할 수 있습니다.
+- **대댓글 기능**: 사용자는 댓글에 대한 대댓글을 작성할 수 있습니다.
+- **댓글 수정 및 삭제**: 사용자는 자신이 작성한 댓글 및 대댓글을 수정하거나 삭제할 수 있습니다.
+
+### 2.3 좋아요 기능
+
+- **좋아요**: 사용자는 게시글에 좋아요를 누를 수 있습니다.
+- **좋아요 취소**: 사용자는 자신이 누른 좋아요를 취소할 수 있습니다.
+
+### 2.4 Direct Message (DM) 기능
+
+- **DM 작성**: 사용자는 다른 사용자와 1:1로 메시지를 주고받을 수 있습니다.
+- **DM 삭제**: 사용자는 자신이 보낸 DM을 삭제할 수 있습니다.
+
+### 구현 계획
+
+### Domain (Entity) 클래스
+
+- 각 테이블에 대응하는 Entity 클래스를 정의하고, JPA 어노테이션을 통해 MySQL 데이터베이스와 매핑합니다.
+
+### Repository 계층
+
+- **JpaRepository**를 확장한 Repository 인터페이스를 정의하여, 기본 CRUD 작업을 자동으로 수행합니다.
+
+### 서비스 계층
+
+- 비즈니스 로직을 처리하며, Repository를 통해 데이터베이스와 상호작용합니다.
+
+### 컨트롤러 계층
+
+- 사용자 요청을 처리하고, 클라이언트와 서버 간의 데이터 교환을 관리합니다.
+
+## 1) 개념적 설계
+
+**1-1) 개체(entity)와 속성(attribute) 추출**
+
+**1. 사용자 (Users)**
+
+- **UserID** (PK) : 사용자 고유 식별자
+- **Username** : 사용자 이름
+- **Email** : 이메일 주소
+- **Password** : 암호
+- **ProfilePicture** : 프로필 사진
+- **Bio** : 사용자 소개
+
+**2. 게시글 (Post)**
+
+- **PostID** (PK) : 게시글 고유 식별자
+- **UserID** (FK) : 게시글 작성자
+- **Image** : 이미지 파일
+- **Caption** : 게시글 내용
+- **Timestamp** : 작성 시간
+
+**3. 댓글 (Comment)**
+
+- **CommentID** (PK) : 댓글 고유 식별자
+- **PostID** (FK) : 댓글이 달린 게시글
+- **UserID** (FK) : 댓글 작성자
+- **Text** : 댓글 내용
+- **Timestamp** : 댓글 작성 시간
+
+**4. 대댓글 (Reply)**
+
+- **ReplyID** (PK) : 대댓글 고유 식별자
+- **CommentID** (FK) : 대댓글이 달린 댓글
+- **UserID** (FK) : 대댓글 작성자
+- **Text** : 대댓글 내용
+- **Timestamp** : 대댓글 작성 시간
+
+**5. 좋아요 (Likes)**
+
+- **LikeID** (PK) : 좋아요 고유 식별자
+- **PostID** (FK) : 좋아요가 달린 게시글
+- **UserID** (FK) : 좋아요를 누른 사용자
+- **Timestamp** : 좋아요 시간
+
+**6. 다이렉트 메시지 (DirectMessage)**
+
+- **MessageID** (PK) : 메시지 고유 식별자
+- **SenderID** (FK) : 메시지 발신자
+- **ReceiverID** (FK) : 메시지 수신자
+- **Text** : 메시지 내용
+- **Timestamp** : 메시지 전송 시간
+
+## 2) 논리적 설계
+
+릴레이션(스키마)
+
+개체 → 릴레이션 이름
+
+속성 → 릴레이션의 속성
+
+![erd](https://github.com/user-attachments/assets/49eea983-2974-45d1-aa0c-f19a31790f66)
+
+## 3) 물리적 설계
+
+**SQL문 작성 예시**
+
+-- 사용자 테이블
+CREATE TABLE User (
+UserID INT PRIMARY KEY AUTO_INCREMENT,
+Username VARCHAR(50) NOT NULL,
+Email VARCHAR(100) NOT NULL UNIQUE,
+Password VARCHAR(100) NOT NULL,
+ProfilePicture VARCHAR(255),
+);
+
+-- 게시글 테이블
+CREATE TABLE Post (
+PostID INT PRIMARY KEY AUTO_INCREMENT,
+UserID INT,
+Image VARCHAR(255),
+Caption TEXT,
+Timestamp DATETIME DEFAULT CURRENT_TIMESTAMP,
+FOREIGN KEY (UserID) REFERENCES User(UserID)
+);
+
+
+테이블이름 user로 했더니 단위테스트에서 오류계속발생..
+
+다른 분들은 잘되는것같길래 안바꾸고 해봤는데 계속 안돼서 users로 테이블 이름 변경하니 성공. .
+
+
+![image (2)](https://github.com/user-attachments/assets/ace93beb-c781-4ab6-a3d2-c5a2ad068f8c)
+
+# REPOSITORY 단위테스트
+
+- `given` : 테스트 실행을 준비하는 단계
+- `when` : 테스트를 진행하는 단계
+- `then` : 테스트 결과를 검증하는 단계
+
diff --git a/build.gradle b/build.gradle
new file mode 100644
index 00000000..db38b6ae
--- /dev/null
+++ b/build.gradle
@@ -0,0 +1,41 @@
+/*plugins {
+	id 'java'
+	id 'org.springframework.boot' version '3.3.3'
+	id 'io.spring.dependency-management' version '1.1.6'
+}*/
+plugins {
+	id 'org.springframework.boot' version '3.1.2'  // 스프링 부트 버전
+	id 'io.spring.dependency-management' version '1.1.0'
+	id 'java'
+}
+group = 'com.ceos20'
+version = '0.0.1-SNAPSHOT'
+
+java {
+	toolchain {
+		languageVersion = JavaLanguageVersion.of(17)
+	}
+}
+
+repositories {
+	mavenCentral()
+}
+
+dependencies {
+	implementation 'org.springframework.boot:spring-boot-starter-web'
+	testImplementation 'org.springframework.boot:spring-boot-starter-test'
+	testImplementation 'org.assertj:assertj-core:3.20.2'
+
+	testRuntimeOnly 'org.junit.platform:junit-platform-launcher'
+	implementation 'org.springframework.boot:spring-boot-starter-data-jpa'
+
+	compileOnly 'org.projectlombok:lombok'
+	annotationProcessor 'org.projectlombok:lombok'
+
+	runtimeOnly 'com.h2database:h2'
+	runtimeOnly 'com.mysql:mysql-connector-j'
+}
+
+tasks.named('test') {
+	useJUnitPlatform()
+}
diff --git a/gradle/wrapper/gradle-wrapper.properties b/gradle/wrapper/gradle-wrapper.properties
new file mode 100644
index 00000000..a4413138
--- /dev/null
+++ b/gradle/wrapper/gradle-wrapper.properties
@@ -0,0 +1,7 @@
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.8-bin.zip
+networkTimeout=10000
+validateDistributionUrl=true
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists
diff --git a/gradlew b/gradlew
new file mode 100644
index 00000000..b740cf13
--- /dev/null
+++ b/gradlew
@@ -0,0 +1,249 @@
+#!/bin/sh
+
+#
+# Copyright © 2015-2021 the original authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+##############################################################################
+#
+#   Gradle start up script for POSIX generated by Gradle.
+#
+#   Important for running:
+#
+#   (1) You need a POSIX-compliant shell to run this script. If your /bin/sh is
+#       noncompliant, but you have some other compliant shell such as ksh or
+#       bash, then to run this script, type that shell name before the whole
+#       command line, like:
+#
+#           ksh Gradle
+#
+#       Busybox and similar reduced shells will NOT work, because this script
+#       requires all of these POSIX shell features:
+#         * functions;
+#         * expansions «$var», «${var}», «${var:-default}», «${var+SET}»,
+#           «${var#prefix}», «${var%suffix}», and «$( cmd )»;
+#         * compound commands having a testable exit status, especially «case»;
+#         * various built-in commands including «command», «set», and «ulimit».
+#
+#   Important for patching:
+#
+#   (2) This script targets any POSIX shell, so it avoids extensions provided
+#       by Bash, Ksh, etc; in particular arrays are avoided.
+#
+#       The "traditional" practice of packing multiple parameters into a
+#       space-separated string is a well documented source of bugs and security
+#       problems, so this is (mostly) avoided, by progressively accumulating
+#       options in "$@", and eventually passing that to Java.
+#
+#       Where the inherited environment variables (DEFAULT_JVM_OPTS, JAVA_OPTS,
+#       and GRADLE_OPTS) rely on word-splitting, this is performed explicitly;
+#       see the in-line comments for details.
+#
+#       There are tweaks for specific operating systems such as AIX, CygWin,
+#       Darwin, MinGW, and NonStop.
+#
+#   (3) This script is generated from the Groovy template
+#       https://github.com/gradle/gradle/blob/HEAD/platforms/jvm/plugins-application/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
+#       within the Gradle project.
+#
+#       You can find Gradle at https://github.com/gradle/gradle/.
+#
+##############################################################################
+
+# Attempt to set APP_HOME
+
+# Resolve links: $0 may be a link
+app_path=$0
+
+# Need this for daisy-chained symlinks.
+while
+    APP_HOME=${app_path%"${app_path##*/}"}  # leaves a trailing /; empty if no leading path
+    [ -h "$app_path" ]
+do
+    ls=$( ls -ld "$app_path" )
+    link=${ls#*' -> '}
+    case $link in             #(
+      /*)   app_path=$link ;; #(
+      *)    app_path=$APP_HOME$link ;;
+    esac
+done
+
+# This is normally unused
+# shellcheck disable=SC2034
+APP_BASE_NAME=${0##*/}
+# Discard cd standard output in case $CDPATH is set (https://github.com/gradle/gradle/issues/25036)
+APP_HOME=$( cd "${APP_HOME:-./}" > /dev/null && pwd -P ) || exit
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD=maximum
+
+warn () {
+    echo "$*"
+} >&2
+
+die () {
+    echo
+    echo "$*"
+    echo
+    exit 1
+} >&2
+
+# OS specific support (must be 'true' or 'false').
+cygwin=false
+msys=false
+darwin=false
+nonstop=false
+case "$( uname )" in                #(
+  CYGWIN* )         cygwin=true  ;; #(
+  Darwin* )         darwin=true  ;; #(
+  MSYS* | MINGW* )  msys=true    ;; #(
+  NONSTOP* )        nonstop=true ;;
+esac
+
+CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
+
+
+# Determine the Java command to use to start the JVM.
+if [ -n "$JAVA_HOME" ] ; then
+    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
+        # IBM's JDK on AIX uses strange locations for the executables
+        JAVACMD=$JAVA_HOME/jre/sh/java
+    else
+        JAVACMD=$JAVA_HOME/bin/java
+    fi
+    if [ ! -x "$JAVACMD" ] ; then
+        die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD=java
+    if ! command -v java >/dev/null 2>&1
+    then
+        die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+fi
+
+# Increase the maximum file descriptors if we can.
+if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
+    case $MAX_FD in #(
+      max*)
+        # In POSIX sh, ulimit -H is undefined. That's why the result is checked to see if it worked.
+        # shellcheck disable=SC2039,SC3045
+        MAX_FD=$( ulimit -H -n ) ||
+            warn "Could not query maximum file descriptor limit"
+    esac
+    case $MAX_FD in  #(
+      '' | soft) :;; #(
+      *)
+        # In POSIX sh, ulimit -n is undefined. That's why the result is checked to see if it worked.
+        # shellcheck disable=SC2039,SC3045
+        ulimit -n "$MAX_FD" ||
+            warn "Could not set maximum file descriptor limit to $MAX_FD"
+    esac
+fi
+
+# Collect all arguments for the java command, stacking in reverse order:
+#   * args from the command line
+#   * the main class name
+#   * -classpath
+#   * -D...appname settings
+#   * --module-path (only if needed)
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, and GRADLE_OPTS environment variables.
+
+# For Cygwin or MSYS, switch paths to Windows format before running java
+if "$cygwin" || "$msys" ; then
+    APP_HOME=$( cygpath --path --mixed "$APP_HOME" )
+    CLASSPATH=$( cygpath --path --mixed "$CLASSPATH" )
+
+    JAVACMD=$( cygpath --unix "$JAVACMD" )
+
+    # Now convert the arguments - kludge to limit ourselves to /bin/sh
+    for arg do
+        if
+            case $arg in                                #(
+              -*)   false ;;                            # don't mess with options #(
+              /?*)  t=${arg#/} t=/${t%%/*}              # looks like a POSIX filepath
+                    [ -e "$t" ] ;;                      #(
+              *)    false ;;
+            esac
+        then
+            arg=$( cygpath --path --ignore --mixed "$arg" )
+        fi
+        # Roll the args list around exactly as many times as the number of
+        # args, so each arg winds up back in the position where it started, but
+        # possibly modified.
+        #
+        # NB: a `for` loop captures its iteration list before it begins, so
+        # changing the positional parameters here affects neither the number of
+        # iterations, nor the values presented in `arg`.
+        shift                   # remove old arg
+        set -- "$@" "$arg"      # push replacement arg
+    done
+fi
+
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
+
+# Collect all arguments for the java command:
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, JAVA_OPTS, and optsEnvironmentVar are not allowed to contain shell fragments,
+#     and any embedded shellness will be escaped.
+#   * For example: A user cannot expect ${Hostname} to be expanded, as it is an environment variable and will be
+#     treated as '${Hostname}' itself on the command line.
+
+set -- \
+        "-Dorg.gradle.appname=$APP_BASE_NAME" \
+        -classpath "$CLASSPATH" \
+        org.gradle.wrapper.GradleWrapperMain \
+        "$@"
+
+# Stop when "xargs" is not available.
+if ! command -v xargs >/dev/null 2>&1
+then
+    die "xargs is not available"
+fi
+
+# Use "xargs" to parse quoted args.
+#
+# With -n1 it outputs one arg per line, with the quotes and backslashes removed.
+#
+# In Bash we could simply go:
+#
+#   readarray ARGS < <( xargs -n1 <<<"$var" ) &&
+#   set -- "${ARGS[@]}" "$@"
+#
+# but POSIX shell has neither arrays nor command substitution, so instead we
+# post-process each arg (as a line of input to sed) to backslash-escape any
+# character that might be a shell metacharacter, then use eval to reverse
+# that process (while maintaining the separation between arguments), and wrap
+# the whole thing up as a single "set" statement.
+#
+# This will of course break if any of these variables contains a newline or
+# an unmatched quote.
+#
+
+eval "set -- $(
+        printf '%s\n' "$DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS" |
+        xargs -n1 |
+        sed ' s~[^-[:alnum:]+,./:=@_]~\\&~g; ' |
+        tr '\n' ' '
+    )" '"$@"'
+
+exec "$JAVACMD" "$@"
diff --git a/gradlew.bat b/gradlew.bat
new file mode 100644
index 00000000..25da30db
--- /dev/null
+++ b/gradlew.bat
@@ -0,0 +1,92 @@
+@rem
+@rem Copyright 2015 the original author or authors.
+@rem
+@rem Licensed under the Apache License, Version 2.0 (the "License");
+@rem you may not use this file except in compliance with the License.
+@rem You may obtain a copy of the License at
+@rem
+@rem      https://www.apache.org/licenses/LICENSE-2.0
+@rem
+@rem Unless required by applicable law or agreed to in writing, software
+@rem distributed under the License is distributed on an "AS IS" BASIS,
+@rem WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+@rem See the License for the specific language governing permissions and
+@rem limitations under the License.
+@rem
+
+@if "%DEBUG%"=="" @echo off
+@rem ##########################################################################
+@rem
+@rem  Gradle startup script for Windows
+@rem
+@rem ##########################################################################
+
+@rem Set local scope for the variables with windows NT shell
+if "%OS%"=="Windows_NT" setlocal
+
+set DIRNAME=%~dp0
+if "%DIRNAME%"=="" set DIRNAME=.
+@rem This is normally unused
+set APP_BASE_NAME=%~n0
+set APP_HOME=%DIRNAME%
+
+@rem Resolve any "." and ".." in APP_HOME to make it shorter.
+for %%i in ("%APP_HOME%") do set APP_HOME=%%~fi
+
+@rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+set DEFAULT_JVM_OPTS="-Xmx64m" "-Xms64m"
+
+@rem Find java.exe
+if defined JAVA_HOME goto findJavaFromJavaHome
+
+set JAVA_EXE=java.exe
+%JAVA_EXE% -version >NUL 2>&1
+if %ERRORLEVEL% equ 0 goto execute
+
+echo. 1>&2
+echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH. 1>&2
+echo. 1>&2
+echo Please set the JAVA_HOME variable in your environment to match the 1>&2
+echo location of your Java installation. 1>&2
+
+goto fail
+
+:findJavaFromJavaHome
+set JAVA_HOME=%JAVA_HOME:"=%
+set JAVA_EXE=%JAVA_HOME%/bin/java.exe
+
+if exist "%JAVA_EXE%" goto execute
+
+echo. 1>&2
+echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME% 1>&2
+echo. 1>&2
+echo Please set the JAVA_HOME variable in your environment to match the 1>&2
+echo location of your Java installation. 1>&2
+
+goto fail
+
+:execute
+@rem Setup the command line
+
+set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
+
+
+@rem Execute Gradle
+"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %*
+
+:end
+@rem End local scope for the variables with windows NT shell
+if %ERRORLEVEL% equ 0 goto mainEnd
+
+:fail
+rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of
+rem the _cmd.exe /c_ return code!
+set EXIT_CODE=%ERRORLEVEL%
+if %EXIT_CODE% equ 0 set EXIT_CODE=1
+if not ""=="%GRADLE_EXIT_CONSOLE%" exit %EXIT_CODE%
+exit /b %EXIT_CODE%
+
+:mainEnd
+if "%OS%"=="Windows_NT" endlocal
+
+:omega
diff --git a/settings.gradle b/settings.gradle
new file mode 100644
index 00000000..19b52044
--- /dev/null
+++ b/settings.gradle
@@ -0,0 +1 @@
+rootProject.name = 'spring-boot'
diff --git a/src/main/java/com/ceos20/springinstagram/SpringInstagramApplication.java b/src/main/java/com/ceos20/springinstagram/SpringInstagramApplication.java
new file mode 100644
index 00000000..f5bee5b9
--- /dev/null
+++ b/src/main/java/com/ceos20/springinstagram/SpringInstagramApplication.java
@@ -0,0 +1,12 @@
+package com.ceos20.springinstagram;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class SpringInstagramApplication {
+
+    public static void main(String[] args) {
+        SpringApplication.run(SpringInstagramApplication.class, args);
+    }
+}
diff --git a/src/main/java/com/ceos20/springinstagram/domain/Comment.java b/src/main/java/com/ceos20/springinstagram/domain/Comment.java
new file mode 100644
index 00000000..3ae69016
--- /dev/null
+++ b/src/main/java/com/ceos20/springinstagram/domain/Comment.java
@@ -0,0 +1,25 @@
+package com.ceos20.springinstagram.domain;
+
+import jakarta.persistence.*;
+import lombok.Data;
+import java.time.LocalDateTime;
+
+@Entity
+@Data
+public class Comment {
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Long commentId;
+
+    @ManyToOne
+    @JoinColumn(name = "postId")
+    private Post post;
+
+    @ManyToOne
+    @JoinColumn(name = "userId")
+    private User user;
+
+    private String text;
+    private LocalDateTime timestamp;
+}
+
diff --git a/src/main/java/com/ceos20/springinstagram/domain/DirectMessage.java b/src/main/java/com/ceos20/springinstagram/domain/DirectMessage.java
new file mode 100644
index 00000000..5b112b8c
--- /dev/null
+++ b/src/main/java/com/ceos20/springinstagram/domain/DirectMessage.java
@@ -0,0 +1,30 @@
+package com.ceos20.springinstagram.domain;
+
+import jakarta.persistence.*;
+import lombok.Data;
+import java.time.LocalDateTime;
+
+@Entity
+@Data
+public class DirectMessage {
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Long messageId;
+
+    @ManyToOne
+    @JoinColumn(name = "senderId")
+    private User sender;
+
+    @ManyToOne
+    @JoinColumn(name = "receiverId")
+    private User receiver;
+
+    private String text;
+    private LocalDateTime timestamp;
+
+    /*@PrePersist
+    protected void onCreate() {
+        timestamp = LocalDateTime.now();
+    }
+    */
+}
diff --git a/src/main/java/com/ceos20/springinstagram/domain/Likes.java b/src/main/java/com/ceos20/springinstagram/domain/Likes.java
new file mode 100644
index 00000000..7eb57486
--- /dev/null
+++ b/src/main/java/com/ceos20/springinstagram/domain/Likes.java
@@ -0,0 +1,23 @@
+package com.ceos20.springinstagram.domain;
+
+import jakarta.persistence.*;
+import lombok.Data;
+import java.time.LocalDateTime;
+
+@Entity
+@Data
+public class Likes {
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Long likeId;
+
+    @ManyToOne
+    @JoinColumn(name = "postId")
+    private Post post;
+
+    @ManyToOne
+    @JoinColumn(name = "userId")
+    private User user;
+
+    private LocalDateTime timestamp;
+}
diff --git a/src/main/java/com/ceos20/springinstagram/domain/Post.java b/src/main/java/com/ceos20/springinstagram/domain/Post.java
new file mode 100644
index 00000000..9a74e1b6
--- /dev/null
+++ b/src/main/java/com/ceos20/springinstagram/domain/Post.java
@@ -0,0 +1,22 @@
+package com.ceos20.springinstagram.domain;
+
+import jakarta.persistence.*;
+import lombok.Data;
+import java.time.LocalDateTime;
+
+@Entity
+@Data
+@Table(name = "post")
+public class Post {
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Long postId;
+
+    @ManyToOne
+    @JoinColumn(name = "userId")
+    private User user;
+    private String image;
+    private String caption;
+    private LocalDateTime timestamp;
+}
+
diff --git a/src/main/java/com/ceos20/springinstagram/domain/Reply.java b/src/main/java/com/ceos20/springinstagram/domain/Reply.java
new file mode 100644
index 00000000..2b332ddc
--- /dev/null
+++ b/src/main/java/com/ceos20/springinstagram/domain/Reply.java
@@ -0,0 +1,24 @@
+package com.ceos20.springinstagram.domain;
+
+import jakarta.persistence.*;
+import lombok.Data;
+import java.time.LocalDateTime;
+
+@Entity
+@Data
+public class Reply {
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Long replyId;
+
+    @ManyToOne
+    @JoinColumn(name = "commentId")
+    private Comment comment;
+
+    @ManyToOne
+    @JoinColumn(name = "userId")
+    private User user;
+
+    private String text;
+    private LocalDateTime timestamp;
+}
diff --git a/src/main/java/com/ceos20/springinstagram/domain/User.java b/src/main/java/com/ceos20/springinstagram/domain/User.java
new file mode 100644
index 00000000..fe3dc835
--- /dev/null
+++ b/src/main/java/com/ceos20/springinstagram/domain/User.java
@@ -0,0 +1,21 @@
+package com.ceos20.springinstagram.domain;
+
+import jakarta.persistence.*;
+import lombok.Data;
+
+@Entity
+@Data
+@Table(name = "users")
+public class User {
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Long userId;
+    @Column(nullable = false)
+    private String username;
+    @Column(nullable = false)
+    private String email;
+    @Column(nullable = false)
+    private String password;
+    private String profilePicture;
+}
+
diff --git a/src/main/java/com/ceos20/springinstagram/repository/CommentRepository.java b/src/main/java/com/ceos20/springinstagram/repository/CommentRepository.java
new file mode 100644
index 00000000..9a56220c
--- /dev/null
+++ b/src/main/java/com/ceos20/springinstagram/repository/CommentRepository.java
@@ -0,0 +1,10 @@
+package com.ceos20.springinstagram.repository;
+import com.ceos20.springinstagram.domain.Post;
+import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.stereotype.Repository;
+import com.ceos20.springinstagram.domain.Comment;
+import java.util.List;
+
+@Repository
+public interface CommentRepository extends JpaRepository<Comment, Long> {
+}
diff --git a/src/main/java/com/ceos20/springinstagram/repository/DirectMessageRepository.java b/src/main/java/com/ceos20/springinstagram/repository/DirectMessageRepository.java
new file mode 100644
index 00000000..7408283a
--- /dev/null
+++ b/src/main/java/com/ceos20/springinstagram/repository/DirectMessageRepository.java
@@ -0,0 +1,10 @@
+package com.ceos20.springinstagram.repository;
+
+import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.stereotype.Repository;
+import com.ceos20.springinstagram.domain.DirectMessage;
+
+@Repository
+public interface DirectMessageRepository extends JpaRepository<DirectMessage, Long> {
+}
+
diff --git a/src/main/java/com/ceos20/springinstagram/repository/LikesRepository.java b/src/main/java/com/ceos20/springinstagram/repository/LikesRepository.java
new file mode 100644
index 00000000..c19d16e3
--- /dev/null
+++ b/src/main/java/com/ceos20/springinstagram/repository/LikesRepository.java
@@ -0,0 +1,10 @@
+package com.ceos20.springinstagram.repository;
+
+import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.stereotype.Repository;
+import com.ceos20.springinstagram.domain.Likes;
+
+@Repository
+public interface LikesRepository extends JpaRepository<Likes, Long> {
+}
+
diff --git a/src/main/java/com/ceos20/springinstagram/repository/PostRepository.java b/src/main/java/com/ceos20/springinstagram/repository/PostRepository.java
new file mode 100644
index 00000000..876e168f
--- /dev/null
+++ b/src/main/java/com/ceos20/springinstagram/repository/PostRepository.java
@@ -0,0 +1,9 @@
+package com.ceos20.springinstagram.repository;
+
+import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.stereotype.Repository;
+import com.ceos20.springinstagram.domain.Post;
+
+@Repository
+public interface PostRepository extends JpaRepository<Post, Long> {
+}
\ No newline at end of file
diff --git a/src/main/java/com/ceos20/springinstagram/repository/ReplyRepository.java b/src/main/java/com/ceos20/springinstagram/repository/ReplyRepository.java
new file mode 100644
index 00000000..18eeb6aa
--- /dev/null
+++ b/src/main/java/com/ceos20/springinstagram/repository/ReplyRepository.java
@@ -0,0 +1,9 @@
+package com.ceos20.springinstagram.repository;
+
+import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.stereotype.Repository;
+import com.ceos20.springinstagram.domain.Reply;
+
+@Repository
+public interface ReplyRepository extends JpaRepository<Reply, Long> {
+}
diff --git a/src/main/java/com/ceos20/springinstagram/repository/UserRepository.java b/src/main/java/com/ceos20/springinstagram/repository/UserRepository.java
new file mode 100644
index 00000000..5c3aa779
--- /dev/null
+++ b/src/main/java/com/ceos20/springinstagram/repository/UserRepository.java
@@ -0,0 +1,10 @@
+package com.ceos20.springinstagram.repository;
+
+import com.ceos20.springinstagram.domain.User;
+import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.stereotype.Repository;
+
+
+@Repository
+public interface UserRepository extends JpaRepository<User, Long> {
+}
diff --git a/src/main/resources/application.yml b/src/main/resources/application.yml
new file mode 100644
index 00000000..9e7db663
--- /dev/null
+++ b/src/main/resources/application.yml
@@ -0,0 +1,18 @@
+spring:
+  datasource:
+    url: jdbc:mysql://localhost:3306/insta
+    username: root
+    password: 1234
+    driver-class-name: com.mysql.cj.jdbc.Driver
+
+  jpa:
+    hibernate:
+      ddl-auto: update
+    show-sql: true
+    properties:
+      hibernate:
+        format_sql: true
+
+logging:
+  level:
+    org.hibernate.SQL: debug
\ No newline at end of file
diff --git a/src/test/java/com/ceos20/springinstagram/SpringInstagramApplicationTests.java b/src/test/java/com/ceos20/springinstagram/SpringInstagramApplicationTests.java
new file mode 100644
index 00000000..343e9762
--- /dev/null
+++ b/src/test/java/com/ceos20/springinstagram/SpringInstagramApplicationTests.java
@@ -0,0 +1,13 @@
+package com.ceos20.springinstagram;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.boot.test.context.SpringBootTest;
+
+@SpringBootTest
+class SpringInstagramApplicationTests {
+
+    @Test
+    void contextLoads() {
+    }
+
+}
\ No newline at end of file
diff --git a/src/test/java/com/ceos20/springinstagram/repository/PostRepositoryTest.java b/src/test/java/com/ceos20/springinstagram/repository/PostRepositoryTest.java
new file mode 100644
index 00000000..19be1069
--- /dev/null
+++ b/src/test/java/com/ceos20/springinstagram/repository/PostRepositoryTest.java
@@ -0,0 +1,90 @@
+package com.ceos20.springinstagram.repository;
+
+import com.ceos20.springinstagram.domain.Post;
+import com.ceos20.springinstagram.domain.User;
+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.orm.jpa.DataJpaTest;
+import org.springframework.test.context.jdbc.Sql;
+
+import jakarta.persistence.EntityManager;
+import java.time.LocalDateTime;
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+@DataJpaTest
+public class PostRepositoryTest {
+
+    @Autowired
+    private PostRepository postRepository;
+
+    @Autowired
+    private UserRepository userRepository;
+
+    @Autowired
+    private EntityManager entityManager; // JPA 쿼리 확인을 위한 EntityManager
+
+    @BeforeEach
+    public void setup() {
+        // Given - 3명의 유저를 저장
+        User user1 = new User();
+        user1.setUsername("user1");
+        user1.setEmail("user1@test.com");
+        user1.setPassword("password1");
+        userRepository.save(user1);
+
+        User user2 = new User();
+        user2.setUsername("user2");
+        user2.setEmail("user2@test.com");
+        user2.setPassword("password2");
+        userRepository.save(user2);
+
+        User user3 = new User();
+        user3.setUsername("user3");
+        user3.setEmail("user3@test.com");
+        user3.setPassword("password3");
+        userRepository.save(user3);
+
+        // Given - 3개의 포스트를 저장
+        Post post1 = new Post();
+        post1.setUser(user1);
+        post1.setImage("image1.jpg");
+        post1.setCaption("caption1");
+        post1.setTimestamp(LocalDateTime.now());
+        postRepository.save(post1);
+
+        Post post2 = new Post();
+        post2.setUser(user2);
+        post2.setImage("image2.jpg");
+        post2.setCaption("caption2");
+        post2.setTimestamp(LocalDateTime.now());
+        postRepository.save(post2);
+
+        Post post3 = new Post();
+        post3.setUser(user3);
+        post3.setImage("image3.jpg");
+        post3.setCaption("caption3");
+        post3.setTimestamp(LocalDateTime.now());
+        postRepository.save(post3);
+
+        // JPA 쿼리를 확인하기 위해 flush
+        entityManager.flush();
+        entityManager.clear();
+    }
+
+    @Test
+    public void givenPosts_whenFindAll_thenReturnPosts() {
+        // When - 모든 포스트를 조회
+        List<Post> posts = postRepository.findAll();
+
+        // Then - 조회된 포스트가 3개인지 확인
+        assertThat(posts).hasSize(3);
+
+        // Then - 각각의 포스트가 올바른지 확인
+        assertThat(posts.get(0).getCaption()).isEqualTo("caption1");
+        assertThat(posts.get(1).getCaption()).isEqualTo("caption2");
+        assertThat(posts.get(2).getCaption()).isEqualTo("caption3");
+    }
+}