DBUtil

package OR3.util;

import com.sun.rowset.CachedRowSetImpl;

import java.sql.*;

public class DBUtil {
    // Declare JDBC Driver
    private static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";

    // Connection
    private static Connection conn = null;

    // Connect to DB
    public static void dbConnect() throws SQLException, ClassNotFoundException {
        // Setting Mysql JDBC Driver
        try {
            Class.forName(JDBC_DRIVER);
        } catch (ClassNotFoundException e) {
            System.out.println("Where is your Mysql JDBC Driver?\n");
            e.printStackTrace();
            throw e;
        }

        System.out.println("Mysql JDBC Driver Registered!");

        // Establish the Mysql Connection
        try {
            conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/OR3","root","1017");
        } catch (SQLException e) {
            System.out.println("Connection Failed! Check output console" + e);
            e.printStackTrace();
            throw e;
        }
    }

    // Close Connection
    public static void dbDisconnect() throws SQLException {
        try {
            if (conn != null && !conn.isClosed()) {
                conn.close();
            }
        } catch (Exception e){
           throw e;
        }
    }

    // DB Execute Query Operation
    public static ResultSet dbExecuteQuery(String queryStmt) throws SQLException, ClassNotFoundException {
        //Declare statement, resultSet and CachedResultSet as null
        Statement stmt = null;
        ResultSet resultSet = null;
        CachedRowSetImpl crs = null;
        try {
            //Connect to DB
            dbConnect();
            System.out.println("Select statement: " + queryStmt + "\n");

            //Create statement
            stmt = conn.createStatement();

            //Execute select (query) operation
            resultSet = stmt.executeQuery(queryStmt);

            // CachedRowSet Implementation
            // In order to prevent "java.sql.SQLRecoverableException: Closed Connection: next" error
            // We are using CachedRowSet
            crs = new CachedRowSetImpl();
            crs.populate(resultSet);
        } catch (SQLException e) {
            System.out.println("Problem occurred at executeQuery operation : " + e);
            throw e;
        } finally {
            if (resultSet != null) {
                //Close resultSet
                resultSet.close();
            }
            if (stmt != null) {
                //Close Statement
                stmt.close();
            }
            //Close connection
            dbDisconnect();
        }
        //Return CachedRowSet
        return crs;
    }

    // DB Execute Update (For Update/Insert/Delete) Operation
    public static void dbExecuteUpdate(String sqlStmt) throws SQLException, ClassNotFoundException {
        //Declare statement as null
        Statement stmt = null;
        try {
            //Connect to DB
            dbConnect();
            //Create Statement
            stmt = conn.createStatement();
            //Run executeUpdate operation with given sql statement
            stmt.executeUpdate(sqlStmt);
        } catch (SQLException e) {
            System.out.println("Problem occurred at executeUpdate operation : " + e);
            throw e;
        } finally {
            if (stmt != null) {
                // Close statement
                stmt.close();
            }
            // Close connection
            dbDisconnect();
        }
    }



    public static boolean isLogin(String userLogin, String pwLogin) throws SQLException {
    		PreparedStatement ps = null;
    		ResultSet rs = null;
    		String query = "SELECT * FROM accounts WHERE user = ? and password = ?";
    		try {
    			ps = conn.prepareStatement(query);
    			ps.setString(1, userLogin);
    			ps.setString(2, pwLogin);

    			rs = ps.executeQuery();
    			if(rs.next()) {
    				return true;
    			}
    			else {
    				return false;
    			}
    		} catch (Exception e) {
    			throw e;
    		}
    }
}