请根据user（uid,uname,upwd）,commodity(cid,cname,cprice,cinventory),cart(cartid,cid,uid,cnum)三个表使用springboot帮我实现购物车功能，包括entity，service、controller、html、repository相关文件和完整代码

好的，我来帮您实现购物车功能。

首先是实体类：

User.java

@Entity
@Table(name = "user")
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "uid")
    private Long uid;

    @Column(name = "uname")
    private String uname;

    @Column(name = "upwd")
    private String upwd;

    // 省略setter和getter
}

Commodity.java

@Entity
@Table(name = "commodity")
public class Commodity {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "cid")
    private Long cid;

    @Column(name = "cname")
    private String cname;

    @Column(name = "cprice")
    private BigDecimal cprice;

    @Column(name = "cinventory")
    private Integer cinventory;

    // 省略setter和getter
}

Cart.java

@Entity
@Table(name = "cart")
public class Cart {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "cartid")
    private Long cartid;

    @Column(name = "cid")
    private Long cid;

    @Column(name = "uid")
    private Long uid;

    @Column(name = "cnum")
    private Integer cnum;

    // 省略setter和getter
}

接下来是DAO层：

UserRepository.java

@Repository
public interface UserRepository extends JpaRepository<User, Long> {
    User findByUname(String uname);
}

CommodityRepository.java

@Repository
public interface CommodityRepository extends JpaRepository<Commodity, Long> {
}

CartRepository.java

@Repository
public interface CartRepository extends JpaRepository<Cart, Long> {
    List<Cart> findByUid(Long uid);
}

然后是Service层：

UserService.java

@Service
public class UserService {
    @Autowired
    private UserRepository userRepository;

    public User findByUname(String uname) {
        return userRepository.findByUname(uname);
    }
}

CommodityService.java

@Service
public class CommodityService {
    @Autowired
    private CommodityRepository commodityRepository;

    public List<Commodity> findAll() {
        return commodityRepository.findAll();
    }

    public Commodity findById(Long cid) {
        return commodityRepository.findById(cid).orElse(null);
    }
}

CartService.java

@Service
public class CartService {
    @Autowired
    private CartRepository cartRepository;

    public List<Cart> findByUid(Long uid) {
        return cartRepository.findByUid(uid);
    }

    public void save(Cart cart) {
        cartRepository.save(cart);
    }

    public void deleteById(Long id) {
        cartRepository.deleteById(id);
    }
}

最后是Controller层：

CartController.java

@Controller
public class CartController {
    @Autowired
    private UserService userService;

    @Autowired
    private CommodityService commodityService;

    @Autowired
    private CartService cartService;

    @GetMapping("/cart")
    public String cart(Model model, HttpServletRequest request) {
        HttpSession session = request.getSession();
        User user = (User)session.getAttribute("user");
        if (user == null) {
            return "redirect:/login";
        }
        List<Cart> cartList = cartService.findByUid(user.getUid());
        model.addAttribute("cartList", cartList);
        return "cart";
    }

    @PostMapping("/cart/add")
    public String addCart(Long cid, Integer cnum, HttpServletRequest request) {
        HttpSession session = request.getSession();
        User user = (User)session.getAttribute("user");
        if (user == null) {
            return "redirect:/login";
        }
        Commodity commodity = commodityService.findById(cid);
        if (commodity == null) {
            return "redirect:/commodity";
        }
        Cart cart = new Cart();
        cart.setUid(user.getUid());
        cart.setCid(cid);
        cart.setCnum(cnum);
        cartService.save(cart);
        return "redirect:/cart";
    }

    @PostMapping("/cart/delete")
    public String deleteCart(Long id) {
        cartService.deleteById(id);
        return "redirect:/cart";
    }
}

最后是HTML页面：

cart.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>购物车</title>
</head>
<body>
    <table>
        <tr>
            <th>商品名称</th>
            <th>商品价格</th>
            <th>商品数量</th>
            <th>操作</th>
        </tr>
        <tr th:each="cart : ${cartList}">
            <td th:text="${commodityService.findById(cart.cid).cname}"></td>
            <td th:text="${commodityService.findById(cart.cid).cprice}"></td>
            <td th:text="${cart.cnum}"></td>
            <td>
                <form method="post" th:action="@{/cart/delete}">
                    <input type="hidden" th:name="id" th:value="${cart.cartid}">
                    <button type="submit">删除</button>
                </form>
            </td>
        </tr>
    </table>
    <form method="post" th:action="@{/cart/add}">
        <select th:name="cid">
            <option th:each="commodity : ${commodityList}" th:value="${commodity.cid}" th:text="${commodity.cname}"></option>
        </select>
        <input type="number" th:name="cnum" min="1">
        <button type="submit">添加到购物车</button>
    </form>
</body>
</html>

以上是购物车功能的完整代码，希望能对您有所帮助。