src/main/java/dev/dao/OrderDao.java

@@ -1,25 +1,61 @@
 package dev.dao;
 
+import dev.database.DatabaseConnection;
 import dev.model.Order;
 
+import java.sql.*;
+import java.util.ArrayList;
 import java.util.List;
 
 public class OrderDao {
 
     public int save(Order order) {
 
-        // TODO:
-        // Insert order and return generated id
+        String sql = "INSERT INTO orders (user_id, total_price) VALUES (?, ?)";
 
+        try (Connection conn = DatabaseConnection.getConnection();
+             PreparedStatement pstmt = conn.prepareStatement(sql, Statement.RETURN_GENERATED_KEYS)) {
+
+            pstmt.setInt(1, order.getUserId());
+            pstmt.setDouble(2, order.getTotalPrice());
+            pstmt.executeUpdate();
+
+            //Generated ID
+            try (ResultSet rs = pstmt.getGeneratedKeys()) {
+                if (rs.next()) {
+                    return rs.getInt(1);
+                }
+            }
+        } catch (SQLException e) {
+            System.err.println("Error saving order: " + e.getMessage());
+        }
         return -1;
     }
 
     public List<Order> findByUserId(int userId) {
+        List<Order> orders = new ArrayList<>();
+        String sql = "SELECT * FROM orders WHERE user_id = ? ORDER BY created_at DESC";
 
-        // TODO:
-        // Retrieve all orders of a user
+        try (Connection conn = DatabaseConnection.getConnection();
+             PreparedStatement pstmt = conn.prepareStatement(sql)) {
 
-        return null;
+            pstmt.setInt(1, userId);
+
+            try (ResultSet rs = pstmt.executeQuery()) {
+                while (rs.next()) {
+                    Order order = new Order(
+                            rs.getInt("id"),
+                            rs.getInt("user_id"),
+                            rs.getTimestamp("created_at"),
+                            rs.getDouble("total_price")
+                    );
+                    orders.add(order);
+                }
+            }
+        } catch (SQLException e) {
+            System.err.println("Error retrieving orders for user: " + e.getMessage());
+        }
+        return orders;
     }
 
 }

src/main/java/dev/dao/OrderDetailDao.java

@@ -1,24 +1,62 @@
 package dev.dao;
 
+import dev.database.DatabaseConnection;
 import dev.model.OrderDetail;
 
+import java.sql.Connection;
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.util.ArrayList;
 import java.util.List;
 
 public class OrderDetailDao {
 
     public void save(OrderDetail detail) {
 
-        // TODO:
-        // Insert order detail
+        String sql = "INSERT INTO order_details (order_id, menu_item_id, quantity, price_at_purchase) VALUES (?, ?, ?, ?)";
 
+        try (Connection conn = DatabaseConnection.getConnection();
+             PreparedStatement pstmt = conn.prepareStatement(sql)) {
+
+            pstmt.setInt(1, detail.getOrderId());
+            pstmt.setInt(2, detail.getMenuItemId());
+            pstmt.setInt(3, detail.getQuantity());
+            pstmt.setDouble(4, detail.getPriceAtPurchase());
+
+            pstmt.executeUpdate();
+
+        } catch (SQLException e) {
+            System.err.println("Error saving order detail: " + e.getMessage());
+        }
     }
 
     public List<OrderDetail> findByOrderId(int orderId) {
 
-        // TODO:
-        // Retrieve order details
+        List<OrderDetail> details = new ArrayList<>();
+        String sql = "SELECT * FROM order_details WHERE order_id = ?";
 
-        return null;
+        try (Connection conn = DatabaseConnection.getConnection();
+             PreparedStatement pstmt = conn.prepareStatement(sql)) {
+
+            pstmt.setInt(1, orderId);
+
+            try (ResultSet rs = pstmt.executeQuery()) {
+                while (rs.next()) {
+                    OrderDetail detail = new OrderDetail(
+                            rs.getInt("id"),
+                            rs.getInt("order_id"),
+                            rs.getInt("menu_item_id"),
+                            rs.getInt("quantity"),
+                            rs.getDouble("price_at_purchase")
+                    );
+                    details.add(detail);
+                }
+            }
+        } catch (SQLException e) {
+            System.err.println("Error retrieving order details: " + e.getMessage());
+        }
+        return details;
     }
 
 }

src/main/java/dev/dao/UserDao.java

@@ -1,22 +1,59 @@
 package dev.dao;
 
+import dev.database.DatabaseConnection;
 import dev.model.User;
 
+import java.sql.*;
+
 public class UserDao {
 
     public boolean save(User user) {
 
-        // TODO:
-        // Insert user into database
+        String sql = "INSERT INTO users (username, password, email) VALUES (?, ?, ?)";
 
-        return false;
+        try (Connection conn = DatabaseConnection.getConnection();
+             PreparedStatement pstmt = conn.prepareStatement(sql)) {
+
+            pstmt.setString(1, user.getUsername());
+            pstmt.setString(2, user.getPassword());
+
+            if (user.getEmail() == null || user.getEmail().trim().isEmpty()) {
+                pstmt.setNull(3, Types.VARCHAR);
+            } else {
+                pstmt.setString(3, user.getEmail());
+            }
+
+            int rowsAffected = pstmt.executeUpdate();
+            return rowsAffected > 0;
+
+        } catch (SQLException e) {
+            System.err.println("Error saving user: " + e.getMessage());
+            return false;
+        }
     }
 
     public User findByUsername(String username) {
 
-        // TODO:
-        // Find a user by username
+        String sql = "SELECT * FROM users WHERE username = ?";
 
+        try (Connection conn = DatabaseConnection.getConnection();
+             PreparedStatement pstmt = conn.prepareStatement(sql)) {
+
+            pstmt.setString(1, username);
+
+            try (ResultSet rs = pstmt.executeQuery()) {
+                if (rs.next()) {
+                    return new User(
+                            rs.getInt("id"),
+                            rs.getString("username"),
+                            rs.getString("password"),
+                            rs.getString("email")
+                    );
+                }
+            }
+        } catch (SQLException e) {
+            System.err.println("Error finding user by username: " + e.getMessage());
+        }
         return null;
     }
 

src/main/java/dev/model/Order.java

@@ -1,5 +1,6 @@
 package dev.model;
 
+import java.sql.Timestamp;
 import java.time.LocalDateTime;
 
 public class Order {
@@ -12,4 +13,18 @@ public class Order {
 
     private double totalPrice;
 
+    public Order(int id, int userId, Timestamp createdAt, double totalPrice) {
+        this.id = id;
+        this.userId = userId;
+        this.createdAt = createdAt.toLocalDateTime();
+        this.totalPrice = totalPrice;
+    }
+
+    public int getUserId() {
+        return userId;
+    }
+
+    public double getTotalPrice() {
+        return totalPrice;
+    }
 }

src/main/java/dev/model/OrderDetail.java

@@ -12,4 +12,27 @@ public class OrderDetail {
 
     private double price;
 
+    public OrderDetail(int id, int orderId, int menuItemId, int quantity, double priceAtPurchase) {
+        this.id = id;
+        this.orderId = orderId;
+        this.menuItemId = menuItemId;
+        this.quantity = quantity;
+        this.price = priceAtPurchase;
+    }
+
+    public int getOrderId() {
+        return orderId;
+    }
+
+    public int getMenuItemId() {
+        return menuItemId;
+    }
+
+    public int getQuantity() {
+        return quantity;
+    }
+
+    public double getPriceAtPurchase() {
+        return price;
+    }
 }

src/main/java/dev/model/User.java

@@ -24,4 +24,12 @@ public class User {
     public int getId() {
         return this.id;
     }
+
+    public String getEmail() {
+        return this.email;
+    }
+
+    public String getPassword() {
+        return this.password;
+    }
 }