[Day 17 | 과제] DAO, DTO, VO 차이(~ing)

1) DAO (Data Access Object) 

DAO는 DB의 데이터에 접근하기 위한 객체.

직접 DB에 접근하여 데이터를 삽입, 삭제, 조회 등 조작할 수 있음 

 

DB 접근 로직과 비즈니스 로직을 분리하기 위해 사용. 

 

이하 나의 DAO: 

DeptDAO.java

package com.my;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;

public class DeptDAO {

	// Singleton
	private static DeptDAO dao = new DeptDAO();
	private DeptDAO(){ }
	public static DeptDAO getInstance() { return dao; }
	/////////////////
	DeptVO selectDept(int deptno, Connection conn) {
		
		DeptVO dept = null;
		try {
			//String sql = "select * from dept where deptno = "+ deptno;
			String sql = "select * from dept10 where deptno = ?";
			//Statement stmt = conn.createStatement();
			PreparedStatement pstmt = conn.prepareStatement(sql);
			pstmt.setInt(1, deptno); 
			ResultSet rs = pstmt.executeQuery();
			
			while(rs.next()) {
				dept = new DeptVO(rs.getInt(1),rs.getString(2),rs.getString("loc"));
				System.out.printf("%d | %-10s | %-10s %n",rs.getInt("deptno"),rs.getString(2),rs.getString("loc"));
			}
			pstmt.close();
			//stmt.close();
		}
		catch (SQLException e) {
			System.out.println("연결 안됨");
		}
		return dept;
	}
	
	int insertDept(DeptVO deptObj, Connection conn) {
		
		int resultCount = 0;
		DeptVO dept = null;

		try {
			String sql = "insert into dept10 values(?,?,?)";
			PreparedStatement pstmt = conn.prepareStatement(sql);
			pstmt.setInt(1, deptObj.getDeptno()); 
			pstmt.setString(2, deptObj.getDname());
			pstmt.setString(3, deptObj.getLoc());
			
			resultCount = pstmt.executeUpdate();
			
			pstmt.close();
		}
		catch (SQLException e) {
			System.out.println("연결 안됨");
		}
		return resultCount;
	}

	int updateDept(DeptVO deptObj,Connection conn) {
		
		int resultCount = 0;
		
		try {
			String sql = "update dept10 set loc = ? where deptno = ?"; ;
			PreparedStatement pstmt = conn.prepareStatement(sql);
			pstmt.setInt(2, deptObj.getDeptno()); 
			pstmt.setString(1, deptObj.getLoc());
			resultCount = pstmt.executeUpdate();
			pstmt.close();
		}
		catch (SQLException e) {
			System.out.println("연결 안됨");
		}
		return resultCount;
	}
	
	int deleteDept(int  deptno,Connection conn ) { 
		int resultCount = 0;
		
		try {
			String sql = "delete from dept10 where deptno = ?"; ;
			PreparedStatement pstmt = conn.prepareStatement(sql);
			pstmt.setInt(1, deptno); 
			resultCount = pstmt.executeUpdate();
			pstmt.close();
		}
		catch (SQLException e) {
			System.out.println("연결 안됨");
		}
		return resultCount;
	}
	
	List<DeptVO> listDept(Connection conn) {
		
		List<DeptVO> deptList = new ArrayList<DeptVO>();

		try {
			
			String sql = "select * from dept10";
			
			PreparedStatement pstmt = conn.prepareStatement(sql);
			ResultSet rs = pstmt.executeQuery();
			
			while(rs.next()) {
				System.out.printf("%d | %-10s | %-10s %n",rs.getInt("deptno"),rs.getString(2),rs.getString("loc"));
				deptList.add(new DeptVO(rs.getInt(1),rs.getString(2),rs.getString(3)));
			}
			pstmt.close();
		}
		catch (SQLException e) {
			System.out.println("연결 안됨");
		}
		return deptList;
	}
	
}

 

 

 

2) DTO (Data Transfer Object)

계층간(Controller, View, Business Layer) 데이터 교환을 위한 자바빈즈(....??)를 의미함

로직을 가지지 않고, getter / setter 메소드만 가진 클래스임. 

- 자바빈즈: 자바로 작성된 소프트웨어 컴포넌트를 지칭하는 단어 

 

 

 

 

3) VO (Value Object)

데이터 그 자체로 의미있는 것을 담고있는 객체 

Read only 속성을 가진 객체

RDB의 레코드에 대응되는 자바 클래스

간단한 독립체( Entity )를 의미하는 작은 객체

VO의 핵심 역할은 equals()와 hashcode() 를 오버라이딩 하는 것. (....??)

 

 

 

이하 나의 VO:

DeptVO.java

package com.my;

// 데이터 객체 
public class DeptVO {
	
	//멤버 필드
	private int deptno;
	private String dname;
	private String loc;
	
	// 생성자 
	DeptVO(){ } // 은닉된 것
	DeptVO(int deptno, String dname, String loc){
		this.deptno = deptno; this.dname = dname; this.loc = loc;  }
	
	// 멤버 메소드 ( 메뉴 source에서 --> Generate getters and setter에서 자동 생성)  
	public int getDeptno() {	return deptno; }
	public String getDname() {	return dname;  }
	public String getLoc() {	return loc;		}	
	@Override
	public String toString() {
		return "DeptVO [deptno=" + deptno + ", dname=" + dname + ", loc=" + loc + ", toString()=" + super.toString()
				+ "]";
	}

}

 

 

Reference: 

https://genesis8.tistory.com/214

DAO / VO / DTO란?

https://ijbgo.tistory.com/9

VO vs DTO

https://velog.io/@ha0kim/DAO-DTO-VO-%EC%B0%A8%EC%9D%B4

DAO, DTO, VO,Entity 차이