회원 관리 Program

: 새로운 회원을 등록, 기존 회원을 검색

사용할 table 생성

CREATE TABLE users (
	id		 VARCHAR(10) NOT NULL PRIMARY KEY,
    name 	 VARCHAR(20) NOT NULL,
    password VARCHAR(20) NOT NULL
);

Layered Architecture

1. Main.java -> main method
2. UserDAO.java -> DAO
3. User.java -> DTO, VO, Entity, Bean

코드

package lecture0722.step1;

import java.sql.SQLException;

public class Main {

	public static void main(String[] args) throws ClassNotFoundException, SQLException {
		
		// Service 없이 main에서 직접 로직처리를 해 보아요.
		UserDAO dao = new UserDAO();
		
		User user = new User();
		user.setId("1");
		user.setName("홍길동");
		user.setPassword("test1234");
		
		dao.insert(user);
		
		System.out.println("새로운 사용자 등록");
		
		User user2 = dao.select("1");
		System.out.println(user2.getName() + ", " + user2.getPassword());
	}
}

---

package lecture0722.step1;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class UserDAO {

	public void insert(User user) throws ClassNotFoundException, SQLException { 
		// 이 함수를 호출한 곳으로 Exception을 던진다.
		// try - catch를 사용하지 않아도 된다.
		Class.forName("com.mysql.cj.jdbc.Driver");
		String jdbc_URL = "jdbc:mysql://localhost:3306/sqldb?characterEncoding=UTF-8&serverTimezone=UTC&useSSL=false";
		Connection con = DriverManager.getConnection(jdbc_URL, "root", "password");
		
		String sql = "INSERT INTO users VALUES(?, ?, ?)";
		PreparedStatement pstmt = con.prepareStatement(sql);
		pstmt.setString(1, user.getId());
		pstmt.setString(2, user.getName());
		pstmt.setString(3, user.getPassword());
		
		pstmt.executeUpdate();
		
		pstmt.close();
		con.close();
	}
	
	public User select(String id) throws ClassNotFoundException, SQLException {
		
		Class.forName("com.mysql.cj.jdbc.Driver");
		String jdbc_URL = "jdbc:mysql://localhost:3306/sqldb?characterEncoding=UTF-8&serverTimezone=UTC&useSSL=false";
		Connection con = DriverManager.getConnection(jdbc_URL, "root", "password");
	
		String sql = "SELECT * FROM users WHERE id = ?";
		PreparedStatement pstmt = con.prepareStatement(sql);
		pstmt.setString(1, id);
		
		ResultSet rs = pstmt.executeQuery();
		rs.next();
		
		User user = new User();
		user.setId(rs.getString("id"));
		user.setName(rs.getString("name"));
		user.setPassword(rs.getString("password"));
		
		rs.close();
		pstmt.close();
		con.close();
		
		return user;
	}
}

---

package lecture0722.step1;

public class User {

	private String id;
	private String name;
	private String password;
	
	public User() {
		
	}

	public String getId() {
		return id;
	}

	public void setId(String id) {
		this.id = id;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String getPassword() {
		return password;
	}

	public void setPassword(String password) {
		this.password = password;
	}
}

class를 작성할 때 주의를 기울여야 하는 것

: 유지 보수성 (어떤 변화가 있을 때 코드를 빠르고, 쉽고, 안정적으로 변화시킬 수 있다.)
-> 코드의 수정이 다른 부분에 영향을 주는 것을 최소화
SoC(Seperation of Concern)
Refactoring -> method extraction 기법을 이용해서 위의 코드를 재구성 해보자

코드

package lecture0722.step2;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class UserDAO {
	
	private Connection getConnection() throws ClassNotFoundException, SQLException {
		Class.forName("com.mysql.cj.jdbc.Driver");
		String jdbc_URL = "jdbc:mysql://localhost:3306/sqldb?characterEncoding=UTF-8&serverTimezone=UTC&useSSL=false";
		Connection con = DriverManager.getConnection(jdbc_URL, "root", "password");
		return con;
	}

	public void insert(User user) throws ClassNotFoundException, SQLException { 
		Connection con = getConnection();	
		
		String sql = "INSERT INTO users VALUES(?, ?, ?)";
		PreparedStatement pstmt = con.prepareStatement(sql);
		pstmt.setString(1, user.getId());
		pstmt.setString(2, user.getName());
		pstmt.setString(3, user.getPassword());
		
		pstmt.executeUpdate();
		
		pstmt.close();
		con.close();
	}
	
	public User select(String id) throws ClassNotFoundException, SQLException {		
		Connection con = getConnection();	
		
		String sql = "SELECT * FROM users WHERE id = ?";
		PreparedStatement pstmt = con.prepareStatement(sql);
		pstmt.setString(1, id);
		
		ResultSet rs = pstmt.executeQuery();
		rs.next();
		
		User user = new User();
		user.setId(rs.getString("id"));
		user.setName(rs.getString("name"));
		user.setPassword(rs.getString("password"));
		
		rs.close();
		pstmt.close();
		con.close();
		
		return user;
	}
}

class를 작성할 때 주의를 기울여야 하는 것

재사용성이 있는 class인가요?
: 위에서 만든 DAO class를 판매하려고 한다.
하지만 getConnection()에서 데이터베이스를 연결하는 것을 고정시켜 놓은 상태이다. 코드를 산 곳에서는 이미 사용하고 있는 데이터베이스가 존재할 것이다. 다른 방법을 써야 한다.
=> 추상 method
상속을 이용해서 데이터베이스 연결을 구현하면 된다.

코드

package lecture0722.step2;

import java.sql.SQLException;

public class Main {

	public static void main(String[] args) throws ClassNotFoundException, SQLException {
		
		// Service 없이 main에서 직접 로직처리를 해 보아요.
		UserDAO dao = new NUserDAO();
		
		User user = new User();
		user.setId("1");
		user.setName("홍길동");
		user.setPassword("test1234");
		
		dao.insert(user);
		
		System.out.println("새로운 사용자 등록");
		
		User user2 = dao.select("1");
		System.out.println(user2.getName() + ", " + user2.getPassword());
	}
}

---

package lecture0722.step2;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public abstract class UserDAO {
	
	protected abstract Connection getConnection() throws ClassNotFoundException, SQLException;

	public void insert(User user) throws ClassNotFoundException, SQLException { 
		Connection con = getConnection();
		
		String sql = "INSERT INTO users VALUES(?, ?, ?)";
		PreparedStatement pstmt = con.prepareStatement(sql);
		pstmt.setString(1, user.getId());
		pstmt.setString(2, user.getName());
		pstmt.setString(3, user.getPassword());
		
		pstmt.executeUpdate();
		
		pstmt.close();
		con.close();
	}
	
	public User select(String id) throws ClassNotFoundException, SQLException {		
		Connection con = getConnection();	
		
		String sql = "SELECT * FROM users WHERE id = ?";
		PreparedStatement pstmt = con.prepareStatement(sql);
		pstmt.setString(1, id);
		
		ResultSet rs = pstmt.executeQuery();
		rs.next();
		
		User user = new User();
		user.setId(rs.getString("id"));
		user.setName(rs.getString("name"));
		user.setPassword(rs.getString("password"));
		
		rs.close();
		pstmt.close();
		con.close();
		
		return user;
	}
}

---

package lecture0722.step2;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

// naver 쪽 개발자가 UserDAO를 이용하기 위해
// subclass를 작성
public class NUserDAO extends UserDAO {

	@Override
	protected Connection getConnection() throws ClassNotFoundException, SQLException {
		// naver 나름대로의 connection 연결방법에 대한 구현이 나오면 된다.
		Class.forName("com.mysql.cj.jdbc.Driver");
		String jdbc_URL = "jdbc:mysql://localhost:3306/sqldb?characterEncoding=UTF-8&serverTimezone=UTC&useSSL=false";
		Connection con = DriverManager.getConnection(jdbc_URL, "root", "password");
		return con;
	}
}

상위 class(UserDAO)에 기본적인 logic 흐름이 구현되어 있다. 이 안에 protected method, abstract method가 있다. 하위 class(NUserDAO)에서 추상 method를 overriding해서 하위 class에 맞도록 기능을 완성한다.
=> Design pattern에서 Template method pattern (Framework에서 많이 사용된다.)

-> class를 상속해서 확장하는 가장 기본적인 방식이다.
-> 변경되지 않는 기능(logic)은 상위 class에서 구현한다. 변경되어야 하는 부분은 하위 class에서 구현한다.

조금 다른 관점에서 살펴보면

객체가 생성되는 관점에서 다시 살펴본다.
UserDAO에는 getConnection이라는 추상 method가 존재한다. 하위 class인 NUserDAO에서 구체적으로 객체를 어떻게 생성할 것인지를 기술하고 있다.
=> 하위 class에서 객체의 구체적인 생성 방법을 결정해서 사용하는 Design pattern을 Factory method pattern이라고 한다.

상속은 나름대로의 제약이 있기 때문에 다른 방식으로 구현해 보자.
class를 분리해서 만든다.

코드

package lecture0722.step3;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class UserDAO {
	
	private SimpleConnectionMaker simpleConnectionMaker;
	
	public UserDAO() {
		simpleConnectionMaker = new SimpleConnectionMaker();
	}

	public void insert(User user) throws ClassNotFoundException, SQLException { 
		Connection con = simpleConnectionMaker.makeNewConnection();
		
		String sql = "INSERT INTO users VALUES(?, ?, ?)";
		PreparedStatement pstmt = con.prepareStatement(sql);
		pstmt.setString(1, user.getId());
		pstmt.setString(2, user.getName());
		pstmt.setString(3, user.getPassword());
		
		pstmt.executeUpdate();
		
		pstmt.close();
		con.close();
	}
	
	public User select(String id) throws ClassNotFoundException, SQLException {		
		Connection con = simpleConnectionMaker.makeNewConnection();
		
		String sql = "SELECT * FROM users WHERE id = ?";
		PreparedStatement pstmt = con.prepareStatement(sql);
		pstmt.setString(1, id);
		
		ResultSet rs = pstmt.executeQuery();
		rs.next();
		
		User user = new User();
		user.setId(rs.getString("id"));
		user.setName(rs.getString("name"));
		user.setPassword(rs.getString("password"));
		
		rs.close();
		pstmt.close();
		con.close();
		
		return user;
	}
}

---

package lecture0722.step3;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

public class SimpleConnectionMaker {

	public Connection makeNewConnection() throws ClassNotFoundException, SQLException{	
		Class.forName("com.mysql.cj.jdbc.Driver");
		String jdbc_URL = "jdbc:mysql://localhost:3306/sqldb?characterEncoding=UTF-8&serverTimezone=UTC&useSSL=false";
		Connection con = DriverManager.getConnection(jdbc_URL, "root", "password");
		return con;
	}
}

-> 수행은 잘 되지만 소스코드를 공개하지 않는 이상 재사용이 힘들다.
UserDAO는 SimpleConnectionMaker class에 종속된다. 두 class가 아주 강하게 묶인다.(tigtly coupled 현상 발생) 오히려 첫번째 코드보다 안 좋아졌다.

=> 한 class 안에 다른 class 이름이 박혀서는 안된다.

어떻게 위의 문제를 해결할까?

: Interface

코드

package lecture0722.step4;

import java.sql.Connection;
import java.sql.SQLException;

public interface ConnectionMaker {

	public Connection makeConnection() throws ClassNotFoundException, SQLException;
}

---

package lecture0722.step4;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

public class NUserDAO implements ConnectionMaker {

	@Override
	public Connection makeConnection() throws ClassNotFoundException, SQLException {
		Class.forName("com.mysql.cj.jdbc.Driver");
		String jdbc_URL = "jdbc:mysql://localhost:3306/sqldb?characterEncoding=UTF-8&serverTimezone=UTC&useSSL=false";
		Connection con = DriverManager.getConnection(jdbc_URL, "root", "password");
		return con;
	}
}

---

package lecture0722.step4;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class UserDAO {
	
	private ConnectionMaker connectionMaker;
	
	public UserDAO() {
		connectionMaker = new NUserDAO();
	}

	public void insert(User user) throws ClassNotFoundException, SQLException { 
		Connection con = connectionMaker.makeConnection();
		
		String sql = "INSERT INTO users VALUES(?, ?, ?)";
		PreparedStatement pstmt = con.prepareStatement(sql);
		pstmt.setString(1, user.getId());
		pstmt.setString(2, user.getName());
		pstmt.setString(3, user.getPassword());
		
		pstmt.executeUpdate();
		
		pstmt.close();
		con.close();
	}
	
	public User select(String id) throws ClassNotFoundException, SQLException {		
		Connection con = connectionMaker.makeConnection();
		
		String sql = "SELECT * FROM users WHERE id = ?";
		PreparedStatement pstmt = con.prepareStatement(sql);
		pstmt.setString(1, id);
		
		ResultSet rs = pstmt.executeQuery();
		rs.next();
		
		User user = new User();
		user.setId(rs.getString("id"));
		user.setName(rs.getString("name"));
		user.setPassword(rs.getString("password"));
		
		rs.close();
		pstmt.close();
		con.close();
		
		return user;
	}
}

-> UserDAO class에서 NUserDAO class 이름이 다시 등장하고 있다.
아직 만들지도 않은 class가 코드에서 등장하고 있다.

어떻게 위의 문제를 해결할까?

: DI(Dependency Injection)

코드

package lecture0722.step5;

import java.sql.Connection;
import java.sql.SQLException;

public interface ConnectionMaker {

	public Connection makeConnection() throws ClassNotFoundException, SQLException;
}

---

package lecture0722.step5;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

public class NUserDAO implements ConnectionMaker {

	@Override
	public Connection makeConnection() throws ClassNotFoundException, SQLException {
		Class.forName("com.mysql.cj.jdbc.Driver");
		String jdbc_URL = "jdbc:mysql://localhost:3306/sqldb?characterEncoding=UTF-8&serverTimezone=UTC&useSSL=false";
		Connection con = DriverManager.getConnection(jdbc_URL, "root", "password");
		return con;
	}
}

---

package lecture0722.step5;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class UserDAO {
	
	private ConnectionMaker connectionMaker;
	
	// 객체를 주입 받는다.
	public UserDAO(ConnectionMaker connectionMaker) {
		this.connectionMaker = connectionMaker;
	}

	public void insert(User user) throws ClassNotFoundException, SQLException { 
		Connection con = connectionMaker.makeConnection();
		
		String sql = "INSERT INTO users VALUES(?, ?, ?)";
		PreparedStatement pstmt = con.prepareStatement(sql);
		pstmt.setString(1, user.getId());
		pstmt.setString(2, user.getName());
		pstmt.setString(3, user.getPassword());
		
		pstmt.executeUpdate();
		
		pstmt.close();
		con.close();
	}
	
	public User select(String id) throws ClassNotFoundException, SQLException {		
		Connection con = connectionMaker.makeConnection();
		
		String sql = "SELECT * FROM users WHERE id = ?";
		PreparedStatement pstmt = con.prepareStatement(sql);
		pstmt.setString(1, id);
		
		ResultSet rs = pstmt.executeQuery();
		rs.next();
		
		User user = new User();
		user.setId(rs.getString("id"));
		user.setName(rs.getString("name"));
		user.setPassword(rs.getString("password"));
		
		rs.close();
		pstmt.close();
		con.close();
		
		return user;
	}
}

---

package lecture0722.step5;

import java.sql.SQLException;

public class Main {

	public static void main(String[] args) throws ClassNotFoundException, SQLException {
		
		// Service 없이 main에서 직접 로직처리를 해 보아요.
		ConnectionMaker connectionMaker = new NUserDAO();
		
		UserDAO dao = new UserDAO(connectionMaker);
		
		User user = new User();
		user.setId("1");
		user.setName("홍길동");
		user.setPassword("test1234");
		
		dao.insert(user);
		
		System.out.println("새로운 사용자 등록");
		
		User user2 = dao.select("1");
		System.out.println(user2.getName() + ", " + user2.getPassword());
	}
}

-> UserDAO class가 다른 class에 종속되지 않는다.

Java Program은 상속 기반이 아니라 Interface 기반으로 코드를 작성해야 한다.

최종 코드

Layered Arcitecture + interface + javaFx

package lecture0722.user;

public class User {

	private String id;
	private String name;
	private String password;
	
	public User() {
		
	}

	public String getId() {
		return id;
	}

	public void setId(String id) {
		this.id = id;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String getPassword() {
		return password;
	}

	public void setPassword(String password) {
		this.password = password;
	}
}

---

package lecture0722.user;

import java.sql.Connection;
import java.sql.SQLException;

public interface ConnectionMaker {

	public Connection makeConnection() throws ClassNotFoundException, SQLException;
}

---

package lecture0722.user;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

public class NUserDAO implements ConnectionMaker {

	@Override
	public Connection makeConnection() throws ClassNotFoundException, SQLException {
		Class.forName("com.mysql.cj.jdbc.Driver");
		String jdbc_URL = "jdbc:mysql://localhost:3306/sqldb?characterEncoding=UTF-8&serverTimezone=UTC&useSSL=false";
		Connection con = DriverManager.getConnection(jdbc_URL, "root", "password");
		return con;
	}
}

---

package lecture0722.user;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class UserDAO {
	
	private ConnectionMaker connectionMaker;
	
	// 객체를 주입 받는다.
	public UserDAO(ConnectionMaker connectionMaker) {
		this.connectionMaker = connectionMaker;
	}

	public void insert(User user) throws ClassNotFoundException, SQLException { 
		Connection con = connectionMaker.makeConnection();
		
		String sql = "INSERT INTO users VALUES(?, ?, ?)";
		PreparedStatement pstmt = con.prepareStatement(sql);
		pstmt.setString(1, user.getId());
		pstmt.setString(2, user.getName());
		pstmt.setString(3, user.getPassword());
		
		pstmt.executeUpdate();
		
		pstmt.close();
		con.close();
	}
	
	public User select(String id) throws ClassNotFoundException, SQLException {		
		Connection con = connectionMaker.makeConnection();
		
		String sql = "SELECT * FROM users WHERE id = ?";
		PreparedStatement pstmt = con.prepareStatement(sql);
		pstmt.setString(1, id);
		
		ResultSet rs = pstmt.executeQuery();
		rs.next();
		
		User user = new User();
		user.setId(rs.getString("id"));
		user.setName(rs.getString("name"));
		user.setPassword(rs.getString("password"));
		
		rs.close();
		pstmt.close();
		con.close();
		
		return user;
	}
}

---

package lecture0722.user;

import java.sql.SQLException;

public class UserService {
	
	private ConnectionMaker connectionMaker;
	private UserDAO dao;
	
	public UserService() {
		connectionMaker = new NUserDAO();
		dao = new UserDAO(connectionMaker);
	}
	
	public void pushUser(User user) throws ClassNotFoundException, SQLException {
		dao.insert(user);
	}
	
	public User findUser(String id) throws ClassNotFoundException, SQLException {
		return dao.select(id);
	}
}

---

package lecture0722.user;

import java.sql.SQLException;

import javafx.application.Application;
import javafx.geometry.Insets;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.TextArea;
import javafx.scene.control.TextField;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.FlowPane;
import javafx.stage.Stage;

public class Main extends Application {
	TextArea textarea;
	Button insertBtn, selectBtn;
	TextField idField, nameField, passwordField;
		
	@Override
	public void start(Stage primaryStage) throws Exception {
				
		UserService userService = new UserService();
		
		// 화면 구성
		BorderPane root = new BorderPane();
		root.setPrefSize(700, 500);  // window 크기
			
		textarea = new TextArea();
		root.setCenter(textarea);  // 화면 center에 textarea를 붙인다.
		
		insertBtn = new Button("User 삽입");
		insertBtn.setPrefSize(150, 40);
		insertBtn.setOnAction(e -> {
			textarea.clear();
			
			User user = new User();
			user.setId(idField.getText());
			user.setName(nameField.getText());
			user.setPassword(passwordField.getText());
			
			try {
				userService.pushUser(user);
			} catch (ClassNotFoundException e1) {
				e1.printStackTrace();
			} catch (SQLException e1) {
				e1.printStackTrace();
			}

			textarea.appendText("새로운 사용자 등록");
			idField.clear();
			nameField.clear();
			passwordField.clear();
		});
		
		idField = new TextField();
		idField.setPrefSize(50, 40);
		nameField = new TextField();
		nameField.setPrefSize(140, 40);
		passwordField = new TextField();
		passwordField.setPrefSize(140, 40);
		
		selectBtn = new Button("User 검색");
		selectBtn.setPrefSize(150, 40);
		selectBtn.setOnAction(e -> {	
			textarea.clear();
					
			User user = null;
			try {
				user = userService.findUser(idField.getText());
			} catch (ClassNotFoundException e1) {
				// TODO Auto-generated catch block
				e1.printStackTrace();
			} catch (SQLException e1) {
				// TODO Auto-generated catch block
				e1.printStackTrace();
			}

			textarea.appendText(user.getName() + ", " + user.getPassword());
			idField.clear();
		});
	
		FlowPane flowPane = new FlowPane();
		flowPane.setPadding(new Insets(10,10,10,10));  // 여백을 준다.
		flowPane.setPrefSize(700, 40);
		flowPane.setHgap(10);
		flowPane.getChildren().add(insertBtn);  // 버튼 부착
		flowPane.getChildren().add(idField);
		flowPane.getChildren().add(nameField);
		flowPane.getChildren().add(passwordField);
		flowPane.getChildren().add(selectBtn);
			
		root.setBottom(flowPane);
		
		Scene scene = new Scene(root);
		primaryStage.setScene(scene);
		primaryStage.show();
	}

	public static void main(String[] args) throws ClassNotFoundException, SQLException {
		launch();
	}
}