complete DAO (and model) package

src/main/java/dev/dao/MenuItemDao.java

@@ -1,23 +1,65 @@
 package dev.dao;
 
+import dev.database.DatabaseConnection;
 import dev.model.MenuItem;
 
+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 MenuItemDao {
 
     public List<MenuItem> findAll() {
 
-        // TODO:
+        String sql = "SELECT id, name, price, category FROM menu_items";
-        // Retrieve all menu items
+        List<MenuItem> items = new ArrayList<>();
 
-        return null;
+        try(Connection conn = DatabaseConnection.getConnection();
+            PreparedStatement stmt = conn.prepareStatement(sql);
+            ResultSet rs = stmt.executeQuery())
+        {
+            while (rs.next())
+            {
+                MenuItem item = new MenuItem();
+                item.setId(rs.getInt("id"));
+                item.setName(rs.getString("name"));
+                item.setPrice(rs.getDouble("price"));
+                item.setCategory(rs.getString("category"));
+                items.add(item);
+            }
+        } catch (SQLException e)
+        {
+            e.printStackTrace();
+        }
+        return items;
     }
 
     public MenuItem findById(int id) {
 
-        // TODO:
+        String sql = "SELECT id, name, price, category FROM menu_items WHERE id = ?";
-        // Find menu item by id
+        try (Connection conn = DatabaseConnection.getConnection();
+             PreparedStatement stmt = conn.prepareStatement(sql))
+        {
+            stmt.setInt(1, id);
+            try (ResultSet rs = stmt.executeQuery())
+            {
+                if (rs.next())
+                {
+                    MenuItem item = new MenuItem();
+                    item.setId(rs.getInt("id"));
+                    item.setName(rs.getString("name"));
+                    item.setPrice(rs.getDouble("price"));
+                    item.setCategory(rs.getString("category"));
+                    return item;
+                }
+            }
+        } catch (SQLException e)
+        {
+            e.printStackTrace();
+        }
 
         return null;
     }

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

@@ -1,25 +1,76 @@
 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:
+        String sql = "INSERT INTO orders (user_id, total_price) VALUES (?, ?)";
-        // Insert order and return generated id
+        try (Connection conn = DatabaseConnection.getConnection();
+             PreparedStatement stmt = conn.prepareStatement(sql, Statement.RETURN_GENERATED_KEYS))
+        {
+            stmt.setInt(1, order.getUserId());
+            stmt.setDouble(2, order.getTotalPrice());
+
+            int affectedRows = stmt.executeUpdate();
+            if (affectedRows == 0)
+            {
+                throw new SQLException("unsuccessful");
+            }
+
+            try (ResultSet generatedKeys = stmt.getGeneratedKeys())
+            {
+                if (generatedKeys.next())
+                {
+                    return generatedKeys.getInt(1);
+                } else
+                {
+                    throw new SQLException("unsuccessful");
+                }
+            }
+        } catch (SQLException e)
+        {
+            e.printStackTrace();
+        }
 
         return -1;
     }
 
     public List<Order> findByUserId(int userId) {
 
-        // TODO:
+        String sql = "SELECT id, user_id, orderDate, total_price FROM orders WHERE user_id = ? ORDER BY orderDate DESC";
-        // Retrieve all orders of a user
+        List<Order> orders = new ArrayList<>();
 
-        return null;
+        try (Connection conn = DatabaseConnection.getConnection();
+             PreparedStatement stmt = conn.prepareStatement(sql))
+        {
+
+            stmt.setInt(1, userId);
+            try (ResultSet rs = stmt.executeQuery())
+            {
+                while (rs.next())
+                {
+                    Order order = new Order();
+                    order.setId(rs.getInt("id"));
+                    order.setUserId(rs.getInt("user_id"));
+                    order.setCreatedAt(rs.getTimestamp("order_date").toLocalDateTime());
+                    order.setTotalPrice(rs.getDouble("total_price"));
+                    orders.add(order);
+                }
+            }
+
+        } catch (SQLException e)
+        {
+            e.printStackTrace();
+        }
+
+        return orders;
     }
 
 }

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

@@ -1,24 +1,73 @@
 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:
+        String sql = "INSERT INTO order_details (order_id, menu_items_id, quantity, price_at_purchase) VALUES (?,?,?,?)";
-        // Insert order detail
+        try (Connection conn = DatabaseConnection.getConnection();
+             PreparedStatement stmt = conn.prepareStatement(sql))
+        {
+            stmt.setInt(2, detail.getOrderId());
+            stmt.setInt(3, detail.getMenuItemId());
+            stmt.setInt(4, detail.getQuantity());
+            stmt.setDouble(5, detail.getPrice());
+
+            int affectedRows = stmt.executeUpdate();
+            if (affectedRows == 0)
+            {
+                throw new SQLException("unsuccessful");
+            }
+
+
+        } catch (SQLException e)
+        {
+            e.printStackTrace();
+        }
 
     }
 
     public List<OrderDetail> findByOrderId(int orderId) {
 
-        // TODO:
+        String sql = "SELECT id, order_id, menu_items_id, quantity, price_at_purchase FROM order_details WHERE order_id = ?";
-        // Retrieve order details
 
-        return null;
+        List<OrderDetail> orderDetails = new ArrayList<>();
+        try (Connection conn = DatabaseConnection.getConnection();
+             PreparedStatement stmt = conn.prepareStatement(sql))
+        {
+
+            stmt.setInt(1, orderId);
+            try (ResultSet rs = stmt.executeQuery())
+            {
+                while (rs.next())
+                {
+                    OrderDetail orderDetail = new OrderDetail();
+                    orderDetail.setId(rs.getInt("id"));
+                    orderDetail.setOrderId(rs.getInt("order_id"));
+                    orderDetail.setMenuItemId(rs.getInt("menu_item_id"));
+                    orderDetail.setQuantity(rs.getInt("quantity"));
+                    orderDetail.setPrice(rs.getDouble("price_at_purchase"));
+
+                    orderDetails.add(orderDetail);
+                }
+            }
+
+        } catch (SQLException e)
+        {
+            e.printStackTrace();
+        }
+
+        return orderDetails;
     }
 
 }

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

@@ -1,23 +1,59 @@
 package dev.dao;
 
+import dev.database.DatabaseConnection;
 import dev.model.User;
 
+import java.sql.Connection;
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+
 public class UserDao {
 
     public boolean save(User user) {
 
-        // TODO:
+        String sql = "INSERT INTO users (username, password, email) VALUES (?, ?, ?)";
-        // Insert user into database
+        try (Connection conn = DatabaseConnection.getConnection();
+             PreparedStatement stmt = conn.prepareStatement(sql))
+        {
+            stmt.setString(1, user.getUsername());
+            stmt.setString(2, user.getPassword());
+            stmt.setString(3, user.getEmail());
 
+            int affectedRows = stmt.executeUpdate();
+            return affectedRows > 0;
+        } catch (SQLException e)
+        {
+            e.printStackTrace();
             return false;
         }
+    }
 
     public User findByUsername(String username) {
 
-        // TODO:
+        String sql = "SELECT id, username, password, email FROM users WHERE username = ?";
-        // Find a user by username
+        try (Connection conn = DatabaseConnection.getConnection();
-
+             PreparedStatement stmt = conn.prepareStatement(sql))
+        {
+            stmt.setString(1, username);
+            try (ResultSet rs = stmt.executeQuery())
+            {
+                if (rs.next())
+                {
+                    User user = new User();
+                    user.setId(rs.getInt("id"));
+                    user.setUsername(rs.getString("username"));
+                    user.setPassword(rs.getString("password"));
+                    user.setEmail(rs.getString("email"));
+                    return user;
+                }
+            }
+        } catch (SQLException e)
+        {
+            e.printStackTrace();
+        }
         return null;
+
     }
 
 }

src/main/java/dev/database/DatabaseConnection.java

@@ -1,15 +1,16 @@
 package dev.database;
 
 import java.sql.Connection;
+import java.sql.DriverManager;
 import java.sql.SQLException;
 
 public class DatabaseConnection {
 
-    private static final String URL = "jdbc:postgresql://localhost:5432/restaurant_db"; // DB Server
+    private static final String URL = "jdbc:postgresql://localhost:5432/restaurant"; // DB Server
 
     private static final String USER = "postgres"; // Your Username
 
-    private static final String PASSWORD = "password"; // Your Password
+    private static final String PASSWORD = "11"; // Your Password
 
     private DatabaseConnection() {
 
@@ -17,11 +18,9 @@ public class DatabaseConnection {
 
     public static Connection getConnection()
             throws SQLException {
-
-        // TODO:
         // Return a valid PostgreSQL connection
+        return DriverManager.getConnection(URL, USER, PASSWORD);
 
-        return null;
     }
 
 }

src/main/java/dev/model/MenuItem.java

@@ -12,4 +12,43 @@ public class MenuItem {
 
     private String category;
 
+    public int getId() {
+        return id;
+    }
+
+    public void setId(int id) {
+        this.id = id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public String getDescription() {
+        return description;
+    }
+
+    public void setDescription(String description) {
+        this.description = description;
+    }
+
+    public double getPrice() {
+        return price;
+    }
+
+    public void setPrice(double price) {
+        this.price = price;
+    }
+
+    public String getCategory() {
+        return category;
+    }
+
+    public void setCategory(String category) {
+        this.category = category;
+    }
 }

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

@@ -12,4 +12,35 @@ public class Order {
 
     private double totalPrice;
 
+    public int getId() {
+        return id;
+    }
+
+    public void setId(int id) {
+        this.id = id;
+    }
+
+    public double getTotalPrice() {
+        return totalPrice;
+    }
+
+    public void setTotalPrice(double totalPrice) {
+        this.totalPrice = totalPrice;
+    }
+
+    public LocalDateTime getCreatedAt() {
+        return createdAt;
+    }
+
+    public void setCreatedAt(LocalDateTime createdAt) {
+        this.createdAt = createdAt;
+    }
+
+    public int getUserId() {
+        return userId;
+    }
+
+    public void setUserId(int userId) {
+        this.userId = userId;
+    }
 }

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

@@ -12,4 +12,43 @@ public class OrderDetail {
 
     private double price;
 
+    public int getId() {
+        return id;
+    }
+
+    public void setId(int id) {
+        this.id = id;
+    }
+
+    public double getPrice() {
+        return price;
+    }
+
+    public void setPrice(double price) {
+        this.price = price;
+    }
+
+    public int getQuantity() {
+        return quantity;
+    }
+
+    public void setQuantity(int quantity) {
+        this.quantity = quantity;
+    }
+
+    public int getMenuItemId() {
+        return menuItemId;
+    }
+
+    public void setMenuItemId(int menuItemId) {
+        this.menuItemId = menuItemId;
+    }
+
+    public int getOrderId() {
+        return orderId;
+    }
+
+    public void setOrderId(int orderId) {
+        this.orderId = orderId;
+    }
 }

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

@@ -10,4 +10,35 @@ public class User {
 
     private String email;
 
+    public int getId() {
+        return id;
+    }
+
+    public void setId(int id) {
+        this.id = id;
+    }
+
+    public String getUsername() {
+        return username;
+    }
+
+    public void setUsername(String username) {
+        this.username = username;
+    }
+
+    public String getPassword() {
+        return password;
+    }
+
+    public void setPassword(String password) {
+        this.password = password;
+    }
+
+    public String getEmail() {
+        return email;
+    }
+
+    public void setEmail(String email) {
+        this.email = email;
+    }
 }