Java 9일차 - MySQL연동

MySQL DB연동 / INSERT, SELECT

//DB.java
package net.bit.day28;

import java.sql.Connection;
import java.sql.DriverManager; //Connection CN = DriverManager.getConnection()

public class DB {
	public static Connection getConnection() {
		Connection CN = null;
		try {
			Class.forName("com.mysql.cj.jdbc.Driver");
			String url = "jdbc:mysql://localhost:3306/naver";
			CN = DriverManager.getConnection(url, "root", "1234");
			System.out.println("DB.java문서 mysql데이터 연결 성공");
		}catch(Exception e) { }
		return CN;
	}
}

//DBTest.java
package net.bit.day28;

import java.util.Scanner;
import java.sql.Connection; //Connection CN은 db서버ip정보, 계정id, 비밀번호
import java.sql.DriverManager; //Connection CN = DriverManager.getConnection()
import java.sql.Statement; //ST = CN.createStatement()
import java.sql.PreparedStatement; //PST = CN.prepareStatement("INSERT INTO / UPDATE");
import java.sql.ResultSet; //RS = ST.executeQuery("SELECT ~ FROM");


public class DBTest {
	Scanner sc = new Scanner(System.in);
	String msg = ""; //insert ~~, select ~~, update where ~~, delete where ~~
	Connection CN;
	Statement ST;
	PreparedStatement PST;
	ResultSet RS;
	
	public DBTest() {
		try {
			DB.getConnection();
		}catch(Exception e) { System.out.println("에러이유 : " + e); }
	}
	
	public void dbInsert() {
		System.out.println("신규데이터 입력");
		try {
			System.out.println("저자입력 >>> "); String a = sc.nextLine();
			System.out.println("제목입력 >>> "); String b = sc.nextLine();
			System.out.println("메모입력 >>> "); String c = sc.nextLine();
			//msg = "insert into bit(author, title, memo) values ('a', 'b', 'c')";
			msg = "insert into bit(author, title, memo) values ('"+a+"', '"+b+"', '"+c+"')";
			ST = CN.createStatement(); //명령어생성
			int OK = ST.executeUpdate(msg); //명령어실행
			System.out.println(a + "데이터 저장 성공했습니다");
		}catch(Exception e) { System.out.println("에러이유 : " + e); }
	}
	
	public void dbSelectAll() {
		System.out.println("전체데이터 출력");
		System.out.println("저자\t 제목\t 메모");
		try {
			msg = "select * from bit"; //단순한 문자열
			ST = CN.createStatement(); //명령어생성
			//실행할때 executeQuery() <= select는 명령어가 다름
			RS = ST.executeQuery(msg); //단순한 문자열msg 변수 쿼리문 적용
			while(RS.next()) {
				String a = RS.getString("author");
				String b = RS.getString("title");
				String c = RS.getString("memo");
				System.out.println(a + "\t" + b + "\t" + c);
			}
		}catch(Exception e) { System.out.println("전체조회 에러이유 : " + e); }
	}
	
	public int dbCount() { return 0; }
	public void dbDelete() { }
	public void dbUpdate() { }
	public void dbDetail() { 
		//저자데이터로 한건
	}
	
	public static void main(String[] args) {
		DBTest ob = new DBTest(); //db연결
		ob.dbSelectAll();
		System.out.println("-------------------------------------------");
		
		//조회가 성공이면 신규등록처리
		ob.dbInsert();
		try { Thread.sleep(500); }catch(Exception e) { }
	}
}