Unit III: JDBC Architecture & Database Connectivity

import java.sql.*;

public class JdbcStudentDemo {
    public static void main(String[] args) {
        String url = "jdbc:mysql://localhost:3306/college_db";
        String user = "root";
        String pass = "password";

        Connection con = null;
        Statement stmt = null;
        ResultSet rs = null;

        try {
            // Step 1: Register Driver
            Class.forName("com.mysql.cj.jdbc.Driver");

            // Step 2: Establish Connection
            con = DriverManager.getConnection(url, user, pass);
            System.out.println("Connection established successfully!");

            // Step 3: Create Statement
            stmt = con.createStatement();

            // Step 4: Execute Query
            String sql = "SELECT roll_no, name, marks FROM students";
            rs = stmt.executeQuery(sql);

            System.out.println("Roll\tName\tMarks");
            while (rs.next()) {
                int roll = rs.getInt("roll_no");
                String name = rs.getString("name");
                double marks = rs.getDouble("marks");
                System.out.println(roll + "\t" + name + "\t" + marks);
            }
        } catch (ClassNotFoundException e) {
            System.out.println("Driver Class Not Found: " + e.getMessage());
        } catch (SQLException e) {
            System.out.println("Database Error: " + e.getMessage());
        } finally {
            // Step 5: Clean up resources
            try {
                if (rs != null) rs.close();
                if (stmt != null) stmt.close();
                if (con != null) con.close();
            } catch (SQLException ex) {
                ex.printStackTrace();
            }
        }
    }
}

String query = "SELECT * FROM users WHERE user = ? AND pass = ?";
PreparedStatement pstmt = con.prepareStatement(query);
pstmt.setString(1, userInput);
pstmt.setString(2, passInput);
ResultSet rs = pstmt.executeQuery();