JDBC 실습1 - select

프로젝트 세팅

1. Maven Project(maven-archetype-quickstart 1.1)
2. pom.xml 의존성 추가

<!-- 자신의 버전에 맞는 mysql 의존성 주입 -->
<dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>8.0.22</version>
</dependency>
<!-- jdk 1.8 사용하기 위해 plugins 추가 -->
<build>
  <plugins>
    <plugin>
      <groupId>org.apache.maven.plugins</groupId>
      <artifactId>maven-compiler-plugin</artifactId>
      <version>3.6.1</version>
      <configuration>
        <source>1.8</source>
        <target>1.8</target>
      </configuration>
    </plugin>
  </plugins>
</build>

프로젝트 실습

목표 : role 테이블의 데이터를 select로 읽어오기

1. Role.java 코드작성

package kr.or.connect.jdbcexam.dto;

//  Source의 Generate를 통해 getter, setter와 toString()을 쉽게 생성할 수 있다.
public class Role {
	private Integer roleId;
	private String description;
	
	public Role() {
		
	}
	
	public Role(Integer roleId, String description) {
		super();
		this.roleId = roleId;
		this.description = description;
	}
	
	public Integer getRoleId() {
		return roleId;
	}
	
	public void setRoleId(Integer roleId) {
		this.roleId = roleId;
	}
	
	public String getDescription() {
		return description;
	}
	
	public void setDescription(String description) {
		this.description = description;
	}
	
	@Override
	public String toString() {
		return "Role [roleId=" + roleId + ", description=" + description + "]";
	}
}

2. RoleDao.java 코드작성

package kr.or.connect.jdbcexam.dao;

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

import kr.or.connect.jdbcexam.dto.Role;

public class RoleDao {
	private static String dburl = "jdbc:mysql://localhost:3306/connectdb?serverTimezone=UTC";
	private static String dbUser = "connectuser";
	private static String dbpasswd = "PASSWORD";
	
	public Role getRole(Integer roleId) {
		Role role = null;
		Connection conn = null;
		PreparedStatement ps = null;
		ResultSet rs = null;
		
		try {
			Class.forName("com.mysql.cj.jdbc.Driver");
			conn = DriverManager.getConnection(dburl, dbUser, dbpasswd);
            
			String sql = "SELECT role_id, description FROM role WHERE role_id = ?";
			ps = conn.prepareStatement(sql);
			ps.setInt(1, roleId);	// 	arg1 : ?의 순서. arg2 : ?의 값
			rs = ps.executeQuery();
			
			if(rs.next()) {
				int id = rs.getInt("role_id");
				String description = rs.getString(2);
				role = new Role(id, description);
			}
		}catch (Exception e) {
			e.printStackTrace();
		}finally {
			if(rs != null) {
				try {
					rs.close();					
				} catch (SQLException e) {
					e.printStackTrace();
				}
			}
			if(ps != null) {
				try {
					ps.close();					
				} catch (SQLException e) {
					e.printStackTrace();
				}
			}
			if(conn != null) {
				try {
					conn.close();					
				} catch (SQLException e) {
					e.printStackTrace();
				}
			}
		}
		return role;
	}
}

3. 실행코드작성

package kr.or.connect.jdbcexam;

import kr.or.connect.jdbcexam.dao.RoleDao;
import kr.or.connect.jdbcexam.dto.Role;

public class JDBCExam1 {
	public static void main(String[] args) {
		RoleDao dao = new RoleDao();
		Role role = dao.getRole(100);
		System.out.println(role);
	}
}

결과