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Back-End Study/DBMS · 2022. 9. 7. fullscreen 넓게보기

JDBC - 9. article DELETE 기능 구현

Ⅸ. article DELETE 기능 구현

1. article DELETE 기능 구현

 - 그냥 article delete를 하면 삭제할 수 있지만, 잘못되면 다른 곳을 제거할 수 있는 위험이 있음

    → 그래서 있을 경우에 제거될 수 있도록 설정해야 함

 - SQLErrorException, DBUtil과 SecSql 추가 및 이를 이용해 article DELETE를 구현

     - SQLErrorException.java에 다음과 같이 입력

package exam_Exception;

public class SQLErrorException extends RuntimeException {
	private Exception origin;

	public SQLErrorException(String message, Exception origin) {
		super(message);
		this.origin = origin;
	}

	public Exception getOrigin() {
		return origin;
	}
}

 

    - DBUtil.java에 다음과 같이 입력

package exam_Util;

import java.sql.*;
import java.util.*;

import exam_Exception.SQLErrorException;

public class DBUtil {
	public static Map<String, Object> selectRow(Connection dbConn, SecSql sql) {
		List<Map<String, Object>> rows = selectRows(dbConn, sql);

		if (rows.size() == 0) {
			return new HashMap<>();
		}

		return rows.get(0);
	}

	public static List<Map<String, Object>> selectRows(Connection dbConn, SecSql sql) throws SQLErrorException {
		List<Map<String, Object>> rows = new ArrayList<>();

		PreparedStatement stmt = null;
		ResultSet rs = null;

		try {
			stmt = sql.getPreparedStatement(dbConn);
			rs = stmt.executeQuery();
			ResultSetMetaData metaData = rs.getMetaData();
			int columnSize = metaData.getColumnCount();

			while (rs.next()) {
				Map<String, Object> row = new HashMap<>();

				for (int columnIndex = 0; columnIndex < columnSize; columnIndex++) {
					String columnName = metaData.getColumnName(columnIndex + 1);
					Object value = rs.getObject(columnName);

					if (value instanceof Long) {
						int numValue = (int) (long) value;
						row.put(columnName, numValue);
					} else if (value instanceof Timestamp) {
						String dateValue = value.toString();
						dateValue = dateValue.substring(0, dateValue.length() - 2);
						row.put(columnName, dateValue);
					} else {
						row.put(columnName, value);
					}
				}

				rows.add(row);
			}
		} catch (SQLException e) {
			throw new SQLErrorException("SQL 예외, SQL : " + sql, e);
		} finally {
			if (rs != null) {
				try {
					rs.close();
				} catch (SQLException e) {
					throw new SQLErrorException("SQL 예외, rs 닫기, SQL : " + sql, e);
				}
			}

			if (stmt != null) {
				try {
					stmt.close();
				} catch (SQLException e) {
					throw new SQLErrorException("SQL 예외, stmt 닫기, SQL : " + sql, e);
				}
			}
		}

		return rows;
	}

	public static int selectRowIntValue(Connection dbConn, SecSql sql) {
		Map<String, Object> row = selectRow(dbConn, sql);

		for (String key : row.keySet()) {
			return (int) row.get(key);
		}

		return -1;
	}

	public static String selectRowStringValue(Connection dbConn, SecSql sql) {
		Map<String, Object> row = selectRow(dbConn, sql);

		for (String key : row.keySet()) {
			return (String) row.get(key);
		}

		return "";
	}

	public static boolean selectRowBooleanValue(Connection dbConn, SecSql sql) {
		Map<String, Object> row = selectRow(dbConn, sql);

		for (String key : row.keySet()) {
			return ((int) row.get(key)) == 1;
		}

		return false;
	}

	public static int insert(Connection dbConn, SecSql sql) {
		int id = -1;

		PreparedStatement stmt = null;
		ResultSet rs = null;

		try {
			stmt = sql.getPreparedStatement(dbConn);
			stmt.executeUpdate();
			rs = stmt.getGeneratedKeys();
			if (rs.next()) {
				id = rs.getInt(1);
			}

		} catch (SQLException e) {
			throw new SQLErrorException("SQL 예외, SQL : " + sql, e);
		} finally {
			if (rs != null) {
				try {
					rs.close();
				} catch (SQLException e) {
					throw new SQLErrorException("SQL 예외, rs 닫기, SQL : " + sql, e);
				}
			}

			if (stmt != null) {
				try {
					stmt.close();
				} catch (SQLException e) {
					throw new SQLErrorException("SQL 예외, stmt 닫기, SQL : " + sql, e);
				}
			}

		}

		return id;
	}

	public static int update(Connection dbConn, SecSql sql) {
		int affectedRows = 0;

		PreparedStatement stmt = null;

		try {
			stmt = sql.getPreparedStatement(dbConn);
			affectedRows = stmt.executeUpdate();
		} catch (SQLException e) {
			throw new SQLErrorException("SQL 예외, SQL : " + sql, e);
		} finally {
			if (stmt != null) {
				try {
					stmt.close();
				} catch (SQLException e) {
					throw new SQLErrorException("SQL 예외, stmt 닫기, SQL : " + sql, e);
				}
			}
		}

		return affectedRows;
	}

	public static int delete(Connection dbConn, SecSql sql) {
		return update(dbConn, sql);
	}
}

 

    - SecSql.java에 다음과 같이 입력

package exam_Util;

import java.sql.*;
import java.util.*;

public class SecSql {
	private StringBuilder sqlBuilder;
	private List<Object> datas;

	@Override
	public String toString() {
		return "sql=" + getFormat() + ", data=" + datas;
	}

	public SecSql() {
		sqlBuilder = new StringBuilder();
		datas = new ArrayList<>();
	}

	public boolean isInsert() {
		return getFormat().startsWith("INSERT");
	}

	public SecSql append(Object... args) {
		if (args.length > 0) {
			String sqlBit = (String) args[0];
			sqlBuilder.append(sqlBit + " ");
		}

		for (int i = 1; i < args.length; i++) {
			datas.add(args[i]);
		}

		return this;
	}

	public PreparedStatement getPreparedStatement(Connection dbConn) throws SQLException {
		PreparedStatement stmt = null;

		if (isInsert()) {
			stmt = dbConn.prepareStatement(getFormat(), Statement.RETURN_GENERATED_KEYS);
		} else {
			stmt = dbConn.prepareStatement(getFormat());
		}

		for (int i = 0; i < datas.size(); i++) {
			Object data = datas.get(i);
			int parameterIndex = i + 1;

			if (data instanceof Integer) {
				stmt.setInt(parameterIndex, (int) data);
			} else if (data instanceof String) {
				stmt.setString(parameterIndex, (String) data);
			}
		}

		return stmt;
	}

	public String getFormat() {
		return sqlBuilder.toString();
	}

	public static SecSql from(String sql) {
		return new SecSql().append(sql);
	}
}

 

 - 그 후, Main.java에 다음과 같이 입력

package exam;

import java.sql.*;
import java.util.*;

import exam_Util.DBUtil;
import exam_Util.SecSql;

public class Main {
	public static void main(String[] args) throws ClassNotFoundException {
		Scanner sc = new Scanner(System.in);

		System.out.println("==프로그램 시작==");

		int lastArticleId = 0;

		while (true) {

			System.out.printf("명령어 ) ");
			String cmd = sc.nextLine().trim();

			if (cmd.equals("exit")) {
				System.out.println("===종료===");
				break;
			}

			if (cmd.equals("article write")) {
				System.out.println("== 게시물 작성 ==");
				int id = lastArticleId + 1;
				System.out.printf("제목 : ");
				String title = sc.nextLine();
				System.out.printf("내용 : ");
				String body = sc.nextLine();

				System.out.printf("%d번글이 생성되었습니다\n", id);

				Article article = new Article(id, title, body);

				Connection conn = null;
				PreparedStatement pstmt = null;

				try {
					Class.forName("com.mysql.jdbc.Driver");
					String url = "jdbc:mysql://127.0.0.1:3306/JDBCTest?useUnicode=true&characterEncoding=utf8&autoReconnect=true&serverTimezone=Asia/Seoul&useOldAliasMetadataBehavior=true&zeroDateTimeNehavior=convertToNull";

					conn = DriverManager.getConnection(url, "root", "");
					System.out.println("연결 성공!");

					String sql = "INSERT INTO article";
					sql += " SET regDate = NOW()";
					sql += ", updateDate = NOW()";
					sql += ", title = '" + title + "'";
					sql += ", `body` = '" + body + "';";

					System.out.println(sql);
					pstmt = conn.prepareStatement(sql);

					int affectedRows = pstmt.executeUpdate();

					System.out.println(affectedRows + "열에 적용됨");

				} catch (ClassNotFoundException e) {
					System.out.println("드라이버 로딩 실패");
				} catch (SQLException e) {
					System.out.println("에러: " + e);
				} finally {
					try {
						if (conn != null && !conn.isClosed()) {
							conn.close();
						}
					} catch (SQLException e) {
						e.printStackTrace();
					}
					try {
						if (pstmt != null && !pstmt.isClosed()) {
							pstmt.close();
						}
					} catch (SQLException e) {
						e.printStackTrace();
					}
				}

				lastArticleId++;

			} else if (cmd.startsWith("article modify ")) {

				int id = Integer.parseInt(cmd.split(" ")[2]);

				System.out.printf("== %d번 게시물 수정 ==\n", id);

				System.out.printf("새 제목 : ");
				String title = sc.nextLine();
				System.out.printf("새 내용 : ");
				String body = sc.nextLine();

				Connection conn = null;
				PreparedStatement pstmt = null;

				try {
					Class.forName("com.mysql.jdbc.Driver");
					String url = "jdbc:mysql://127.0.0.1:3306/JDBCTest?useUnicode=true&characterEncoding=utf8&autoReconnect=true&serverTimezone=Asia/Seoul&useOldAliasMetadataBehavior=true&zeroDateTimeNehavior=convertToNull";

					conn = DriverManager.getConnection(url, "root", "");
					System.out.println("연결 성공!");

					String sql = "UPDATE article";
					sql += " SET updateDate = NOW()";
					sql += ", title = '" + title + "'";
					sql += ", `body` = '" + body + "'";
					sql += " WHERE id = " + id + ";";

					System.out.println(sql);
					pstmt = conn.prepareStatement(sql);

					int affectedRows = pstmt.executeUpdate();

					System.out.println(affectedRows + "열에 적용됨");

				} catch (ClassNotFoundException e) {
					System.out.println("드라이버 로딩 실패");
				} catch (SQLException e) {
					System.out.println("에러: " + e);
				} finally {
					try {
						if (conn != null && !conn.isClosed()) {
							conn.close();
						}
					} catch (SQLException e) {
						e.printStackTrace();
					}
					try {
						if (pstmt != null && !pstmt.isClosed()) {
							pstmt.close();
						}
					} catch (SQLException e) {
						e.printStackTrace();
					}
				}

				System.out.printf("%d번 게시물이 수정 되었습니다.\n", id);

			} else if (cmd.startsWith("article delete ")) {
				int id = Integer.parseInt(cmd.split(" ")[2]);

				Connection conn = null;
				PreparedStatement pstmt = null;

				try {
					Class.forName("com.mysql.jdbc.Driver");
					String url = "jdbc:mysql://127.0.0.1:3306/JDBCTest?useUnicode=true&characterEncoding=utf8&autoReconnect=true&serverTimezone=Asia/Seoul&useOldAliasMetadataBehavior=true&zeroDateTimeNehavior=convertToNull";

					conn = DriverManager.getConnection(url, "root", "");
					System.out.println("연결 성공!");
					SecSql sql = new SecSql();
					sql.append("SELECT COUNT(*)");
					sql.append("FROM article");
					sql.append("WHERE id = ?", id);

					int articlesCount = DBUtil.selectRowIntValue(conn, sql);

					if (articlesCount == 0) {
						System.out.printf("%d번 게시글은 존재하지 않습니다.\n", id);
						continue;
					}

					System.out.printf("== %d번 게시물 삭제 ==\n", id);

					sql = new SecSql();
					sql.append("DELETE FROM article");
					sql.append("WHERE id = ?", id);

					DBUtil.delete(conn, sql);

					System.out.printf("%d번 게시물이 삭제 되었습니다\n", id);

				} catch (ClassNotFoundException e) {
					System.out.println("드라이버 로딩 실패");
				} catch (SQLException e) {
					System.out.println("에러: " + e);
				} finally {
					try {
						if (conn != null && !conn.isClosed()) {
							conn.close();
						}
					} catch (SQLException e) {
						e.printStackTrace();
					}
					try {
						if (pstmt != null && !pstmt.isClosed()) {
							pstmt.close();
						}
					} catch (SQLException e) {
						e.printStackTrace();
					}
				}

			} else if (cmd.equals("article list")) {
				System.out.println("== 게시물 리스트 ==");

				Connection conn = null;
				PreparedStatement pstmt = null;
				ResultSet rs = null;

				List<Article> articles = new ArrayList<>();

				try {
					Class.forName("com.mysql.jdbc.Driver");
					String url = "jdbc:mysql://127.0.0.1:3306/JDBCTest?useUnicode=true&characterEncoding=utf8&autoReconnect=true&serverTimezone=Asia/Seoul&useOldAliasMetadataBehavior=true&zeroDateTimeNehavior=convertToNull";

					conn = DriverManager.getConnection(url, "root", "");
					System.out.println("연결 성공!");

					String sql = "SELECT *";
					sql += " FROM article";
					sql += " ORDER BY id DESC";

					System.out.println(sql);

					pstmt = conn.prepareStatement(sql);
					rs = pstmt.executeQuery();

					while (rs.next()) {
						int id = rs.getInt("id");
						String regDate = rs.getString("regDate");
						String updateDate = rs.getString("updateDate");
						String title = rs.getString("title");
						String body = rs.getString("body");

						Article article = new Article(id, regDate, updateDate, title, body);
						articles.add(article);
					}

				} catch (ClassNotFoundException e) {
					System.out.println("드라이버 로딩 실패");
				} catch (SQLException e) {
					System.out.println("에러: " + e);
				} finally {
					try {
						if (rs != null && !rs.isClosed()) {
							rs.close();
						}
					} catch (SQLException e) {
						e.printStackTrace();
					}
					try {
						if (pstmt != null && !pstmt.isClosed()) {
							pstmt.close();
						}
					} catch (SQLException e) {
						e.printStackTrace();
					}
					try {
						if (conn != null && !conn.isClosed()) {
							conn.close();
						}
					} catch (SQLException e) {
						e.printStackTrace();
					}
				}

				if (articles.size() == 0) {
					System.out.println("게시물이 없습니다");
					continue;
				}

				System.out.println("번호    |    제목");

				for (int i = 0; i < articles.size(); i++) {
					Article article = articles.get(i);
					System.out.printf("%4d    |    %s\n", article.id, article.title);
				}
			}

		}
	}

}

 

2. 실행

 - 테이블이 다음과 같이 있다고 가정

 

 - article delete 2를 입력하여 2번째 행을 제거

 

 - 확인 (2번째 행이 제거됨)

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