[JDBC] DAO 를 활용한 쿼리문 작성 1 (insert, update, delete)

public class UserDAO {
    
    public void insert(){}
    public void update(){}
    public void delete(){}
    
}

int num = pstmt.executeUpdate();

1. Insert문

public int insert(String username,String password,String phone){
        Connection conn = DBConnection.getInstance();  // 소켓 연결

        try{
            String sql = "insert into user_tb(username,password,phone) values(?,?,?)";
						//쿼리문 작성 
            PreparedStatement pstmt = conn.prepareStatement(sql);  // 쿼리문을 버퍼에 담음
						pstmt.setString(1,username);  // 매개변수 값을 ? 에 대입
            pstmt.setString(2,password);
            pstmt.setString(3,phone);
            
            int num = pstmt.executeUpdate(); // 쿼리문 전송, 응답은 num에 담음
            return num ; // num = 1 , 1개의 테이블이 변화 , num = 0 테이블 변화없음

        }catch (Exception e){
            e.printStackTrace();
        }
        return -1 ;     // -1 은 오류
    }

import org.junit.jupiter.api.Test;

public class UserDAOTest {
    @Test
    public void inset_test() {
        //given = 매개변수
        String username = "kim";
        String password = "1234";
        String phone = " 01012345678";

        //when = 실행
        UserDAO dao = new UserDAO();
        int result = dao.insert(username, password, phone);

        //then = 결과
        if (result == 1) {
            System.out.println("성공");
        } else if (result == 0) {
            System.out.println("값의 변화가 없습니다.");
        } else {
            System.out.println("실패");
        }

    }
}

2. Delete

public int delete(int number){
        Connection conn = DBConnection.getInstance();
        try {
            String sql = "delete from user_tb where number = ? ";

            PreparedStatement pstmt = conn.prepareStatement(sql);
            pstmt.setInt(1,number);
            int num = pstmt.executeUpdate();  // 
            return num;
        } catch (Exception e) {
            e.printStackTrace(); 

        }
        return -1;    }

@Test
    public void delete_test(){
        //given
        int number = 1;

        //when
        UserDAO dao = new UserDAO() ;
        int result = dao.delete(number);

        //then
        if (result == 1) {
            System.out.println("성공");
        } else if (result == 0) {
            System.out.println(number + "번호를 찾을 수 없습니다.");
        } else {
            System.out.println("실패");
        }
    }

3. Update

public int update(String password, int number) {
        Connection conn = DBConnection.getInstance();
        try {
            String sql = "UPDATE user_tb set password = ? WHERE number =?  ";

            PreparedStatement pstmt = conn.prepareStatement(sql);
            pstmt.setString(1, password);
            pstmt.setInt(2, number);
            int num = pstmt.executeUpdate();  // flush 코드
            return num;
        } catch (Exception e) {
            e.printStackTrace();  //throw new RuntimeException(e); 이거는 오류를 메인에 던짐

        }
        return -1;  // 오류값을

    }

@Test
    public void update(){
        //given
        String password = "9876";
        int number = 2;

        UserDAO dao = new UserDAO() ;
        int result = dao.update(password,number);

        //then
        if (result == 1) {
            System.out.println("성공");
        } else if (result == 0) {
            System.out.println(number + "번호를 찾을 수 없습니다.");
        } else {
            System.out.println("실패");
        }
    }