aswi2020horky-gitlab/project/Deserializer/src/io/Database.java @ c670fa2f

package io;

import java.sql.Blob;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

/**
 * https://www.tutorialspoint.com/jdbc/jdbc-db-connections.htm
 * https://www.tutorialspoint.com/jdbc/jdbc-sample-code.htm
 */
public class Database {

	public static class DB_Messenger {
		public String driver;
		public String url;
		public String user;
		public String password;
		public String sql;
		public String column;

		public DB_Messenger(String driver, String url, String user, String password, String table, String condition, String column) {
			this.driver = driver;
			//The timezone statement added due to MySQL DB. Is it OK with MsSQL and Oracle?
			this.url = url + "?useTimezone=true&serverTimezone=UTC";
			this.user = user;
			this.password = password;

			this.sql = "SELECT " + column + " FROM " + table;
			if(condition.length() > 0)
			{
				this.sql += " WHERE " + condition;
			}
			this.sql += ";";

			this.column = column;
		}
		
		@Override
		public String toString() {
			return "DRIVER: " + driver + "\nURL: " + url + "\nUSER: " + user + "\nPASSWORD: " + password + "\nSQL: " + sql + "\nCOLUMN: " + column;
		}
	}

	public static byte[] getBlobBytes(DB_Messenger crate) {
		Connection conn = null;
		Statement stmt = null;
		byte result[] = null;

		try {
			
			Class.forName(crate.driver);
			
			// The second way of the driver registration.
			//DriverManager.registerDriver(new com.microsoft.sqlserver.jdbc.SQLServerDriver());

			System.out.println("--- Connecting to the database ---".toUpperCase());

			conn = DriverManager.getConnection(crate.url, crate.user, crate.password);

			System.out.println("--- Executing the query ---".toUpperCase());
			stmt = conn.createStatement();
			ResultSet rs = stmt.executeQuery(crate.sql);

			while (rs.next()) {
				Blob blob = rs.getBlob(crate.column);
				if (blob != null && blob.length() > 0) {
					result = blob.getBytes(1l, (int) blob.length());
					System.out.println("--- The BLOB was found ---".toUpperCase());
					break;
				}
			}

			rs.close();
			stmt.close();
			conn.close();
			
		} catch (SQLException e) {
			e.printStackTrace();
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			try {
				stmt.close();
			} catch (Exception e) {}
			try {
				conn.close();
			} catch (Exception e) {}
		}
		
		return result;
	}
	
}