我需要为我的一个uni项目序列化java对象，但我在java方面没有太多经验。我想知道为什么当我尝试打印 toJson 时它不断返回一个空对象以及为什么它不在文件中写入任何内容。
这是我的代码
import java.util.*;
import java.util.stream.Collectors;
import java.io.*;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
public class UniShop {
private static User currentUser;
private static ArrayList<Buyer> buyers;
public static List<Product> products;
public static ArrayList<Order> orders;
private static ArrayList<Reseller> resellers;
public UniShop() {
buyers = new ArrayList<>();
products = new ArrayList<>();
orders = new ArrayList<>();
resellers = new ArrayList<>();
}
public static void addBuyer(Buyer buyer) {
buyers.add(buyer);
}
public static void addReseller(Reseller reseller) {
resellers.add(reseller);
}
public static void placeOrder(Order order) {
orders.add(order);
}
public void confirmArrival(Product product) {
// TODO: Confirming arrival of a product
}
public void Payment(Order order) {
// TODO: Select order payment type, validate payment, etc...
}
private static User findUserByUID(String uid) {
for (Buyer buyer : buyers) {
if (buyer.getUid().equals(uid)) {
return buyer;
}
}
for (Reseller reseller : resellers) {
if (reseller.getUid().equals(uid)) {
return reseller;
}
}
return null; // User not found
}
public static void followUser() {
Scanner scanner = new Scanner(System.in);
System.out.println("Follow/Like User Menu:");
System.out.println("[1] Follow a Buyer");
System.out.println("[2] Like a Reseller");
System.out.println("[3] Go Back");
System.out.print("Enter your choice: ");
int choice = scanner.nextInt();
scanner.nextLine(); // Consume the newline character
switch (choice) {
case 1:
followBuyer(scanner);
break;
case 2:
followReseller(scanner);
break;
case 3:
// Go back to the main menu
break;
default:
System.out.println("Invalid choice. Please enter a valid option.");
}
}
// Follow a buyer based on UID
private static void followBuyer(Scanner scanner) {
System.out.print("Enter the UID of the buyer you want to follow: ");
String uid = scanner.nextLine();
Buyer buyerToFollow = (Buyer) findUserByUID(uid);
if (buyerToFollow != null) {
currentUser.followBuyer(buyerToFollow);
System.out.println("You are now following the buyer: " + buyerToFollow.getFullName());
} else {
System.out.println("Buyer with UID " + uid + " not found.");
}
}
// Follow a reseller based on UID
private static void followReseller(Scanner scanner) {
System.out.print("Enter the UID of the reseller you want to 'like': ");
String uid = scanner.nextLine();
Reseller resellerToFollow = (Reseller) findUserByUID(uid);
if (resellerToFollow != null) {
currentUser.followReseller(resellerToFollow);
System.out.println("You have 'like'd reseller: " + resellerToFollow.getFullName());
} else {
System.out.println("Reseller with UID " + uid + " not found.");
}
}
public static List<Product> SearchProductsByName(String productName) {
return products.stream()
.filter(product -> product.getName().equalsIgnoreCase(productName))
.collect(Collectors.toList());
}
public static List<Product> SearchProductsByCategory(int category) {
List<Product> ProductSearch = new ArrayList<>();
for (Product product : products) {
if (product.getCategory() == category) {
ProductSearch.add(product);
}
}
return ProductSearch;
}
public static List<Product> SearchProductsByReseller(String resellerName) {
List<Product> ProductSearch = new ArrayList<>();
for (Product product : products) {
if (product.getReseller().getFullName().equalsIgnoreCase(resellerName)) {
ProductSearch.add(product);
}
}
return ProductSearch;
}
public static List<Product> SearchProductsByPrice() {
System.out.println("[1] Low -> High");
System.out.println("[2] High -> Low");
List<Product> ProductSearch = new ArrayList<>();
Scanner scanner = new Scanner(System.in);
int choice = 0;
try {
choice = scanner.nextInt();
} catch (InputMismatchException e) {
System.out.println("Invalid input. Please enter a valid number for your choice.");
scanner.nextLine();
SearchProductsByPrice();
}
if (choice == 1) {
// Sort products by price Low -> High then return
ProductSearch = Sort(1);
} else if (choice == 2) {
// Sort products by price High -> Low then return
ProductSearch = Sort(2);
} else {
System.out.println("Invalid Option");
}
return ProductSearch;
}
public static List<Product> SearchProductsByRating() {
return Sort(3);
}
public static List<Product> SearchProductsByLikes() {
return Sort(4);
}
public static List<Product> SearchProductsByPromotions() {
return Sort(5);
}
// TODO: Implement the different sorts
private static List<Product> Sort(int choice) {
List<Product> ProductList = products;
// Price Low -> High
if (choice == 1) {
ProductList.sort(Comparator.comparing(Product::getPrice));
// Price High -> Low
} else if (choice == 2) {
ProductList.sort(Comparator.comparing(Product::getPrice).reversed());
// Likes High -> Low
} else if (choice == 3) {
ProductList.sort(Comparator.comparing(Product::getLikes).reversed());
// Average Rating High -> Low
} else if (choice == 4) {
ProductList.sort(Comparator.comparing(Product::getAverageRating).reversed());
// Promotion True/False
} else if (choice == 5) {
ProductList = ProductList.stream().filter(Product::isPromotion).collect(Collectors.toList());
}
return ProductList;
}
public Buyer ValidateBuyerUID(String UID) {
for (Buyer buyer : buyers) {
if (buyer.getUid().equals(UID)) {
return buyer; // Buyer found, return the buyer
}
}
return null;
}
public Reseller ValidateResellerUID(String UID) {
for (Reseller reseller : resellers) {
if (reseller.getUid().equals(UID)) {
return reseller; // Reseller found, return the reseller
}
}
return null;
}
// TODO: More functionalities to come
public void Registration() {
System.out.println("Welcome to UniShop:");
System.out.println("[1] Register");
System.out.println("[2] Sign In");
System.out.println("[3] Continue as a guest");
System.out.println("[4] Exit");
}
// Sign up as a buyer or Reseller
public void SignUp(Scanner scanner) {
System.out.println("[1] Register as a Buyer");
System.out.println("[2] Register as a Reseller");
int choice = 0;
try {
choice = scanner.nextInt();
} catch (InputMismatchException e) {
System.out.println("Invalid input. Please enter a valid number for your choice.");
scanner.nextLine();
SignUp(scanner);
}
String FirstName, LastName, UID, Email, Address, Password;
switch (choice) {
case 1 -> {
// Register a buyer and add them to the ArrayList
// ...
// TODO: Implement Logic For Validating Registration information ie: Pattern
// matching per profile attributes
// ...
try {
scanner.nextLine();
System.out.print("Enter buyer's first name: ");
FirstName = scanner.nextLine();
System.out.print("Enter buyer's last name: ");
LastName = scanner.nextLine();
System.out.print("Enter Unique Identifier: ");
UID = scanner.nextLine();
System.out.print("Enter buyer's email: ");
Email = scanner.nextLine();
System.out.print("Enter buyer's address: ");
Address = scanner.nextLine();
System.out.print("Enter buyer's password: ");
Password = scanner.nextLine();
Buyer buyer = new Buyer(FirstName, LastName, UID, Email, Address, Password);
addBuyer(buyer);
} catch (InputMismatchException e) {
System.out.println("Invalid input. Please enter a valid number for your choice.");
scanner.nextLine();
SignUp(scanner);
}
}
case 2 -> {
// Register a reseller and add them to the ArrayList
// ...
// TODO: Implement Logic For Validating Registration information ie: Pattern
// matching per profile attributes
// ...
try {
scanner.nextLine();
System.out.print("Enter reseller's first name: ");
FirstName = scanner.nextLine();
System.out.print("Enter reseller's last name: ");
LastName = scanner.nextLine();
System.out.print("Enter Unique Identifier: ");
UID = scanner.nextLine();
System.out.print("Enter reseller's email: ");
Email = scanner.nextLine();
System.out.print("Enter reseller's address: ");
Address = scanner.nextLine();
System.out.print("Enter reseller's password: ");
Password = scanner.nextLine();
Reseller reseller = new Reseller(FirstName, LastName, UID, Email, Address, Password);
addReseller(reseller);
} catch (InputMismatchException e) {
System.out.println("Invalid input. Please enter a valid number for your choice.");
scanner.nextLine();
SignUp(scanner);
}
}
default -> System.out.println("Invalid choice. Please enter a valid option.");
}
}
public boolean SignIn(Scanner scanner) {
// Sign in as a Buyer or a Reseller
System.out.println("[1] Sign in as a Buyer");
System.out.println("[2] Sign in as a Reseller");
int choice = 0;
String UID = null;
try {
choice = scanner.nextInt();
scanner.nextLine();
System.out.print("Enter your Unique Identifier (UID): ");
UID = scanner.nextLine();
} catch (InputMismatchException e) {
System.out.println("Invalid input. Please enter a valid number for your choice.");
scanner.nextLine();
SignIn(scanner);
}
switch (choice) {
case 1 -> {
// Sign in as a buyer
Buyer signedInBuyer = ValidateBuyerUID(UID);
if (signedInBuyer != null) {
System.out.println("Sign-in as buyer successful. Welcome, " + signedInBuyer.getFirstName() + "!");
currentUser = signedInBuyer;
return true;
} else {
System.out.println("Sign-in as buyer failed. UID not found.");
return false;
}
}
case 2 -> {
// Sign in as a reseller
Reseller signedInReseller = ValidateResellerUID(UID);
if (signedInReseller != null) {
System.out.println(
"Sign-in as reseller successful. Welcome, " + signedInReseller.getFirstName() + "!");
currentUser = signedInReseller;
return true;
} else {
System.out.println("Sign-in as reseller failed. UID not found.");
return false;
}
}
default -> System.out.println("Invalid choice. Please enter a valid option.");
}
return false;
}
public void run() {
Scanner scanner = new Scanner(System.in);
boolean running = true;
while (running) {
// Sign Up and Registration Display -> Main Menu
Registration();
int choice = 0;
try {
choice = scanner.nextInt();
} catch (InputMismatchException e) {
System.out.println("Invalid input. Please enter a valid number for your choice.");
scanner.nextLine();
Registration();
}
switch (choice) {
case 1 -> SignUp(scanner);
case 2 -> {
if (SignIn(scanner)) {
int menuChoice;
do {
menuChoice = currentUser.displayMenu(scanner);
if (menuChoice >= 1 && menuChoice <= 5) {
currentUser.sendToFunction(menuChoice, currentUser);
} else {
menuChoice = 6;
}
} while (menuChoice != 6);
}
}
case 3 -> {
}
case 4 -> running = false;
default -> System.out.println("Invalid choice. Please enter a valid option.");
}
}
System.out.println("Thank you for using UniShop!");
}
public static void main(String[] args) throws IOException {
UniShop uniShop = new UniShop();
Reseller Abby = new Reseller("Abby", "Dunham", "abbdun", "[email protected]", "2022 Abby rd", "abbdun");
Reseller Shmidt = new Reseller("Shmidt", "Adams", "shmadms", "[email protected]", "2122 Shmidt rd", "shmadms");
Reseller Christy = new Reseller("Christy", "Christo", "cristo", "[email protected]", "4122 rue LaPoule",
"cristo");
Reseller AnneSophie = new Reseller("Anne-Sophie", "Gauthier", "aneeso", "[email protected]",
"4422 ave Victoria", "aneeso");
Reseller Mathieu = new Reseller("Mathieu", "LeBlanc", "matleb", "[email protected]",
"4022 boul LeBlanc", "matleb");
Product Laptop = new Product("Asus Laptop", Abby, 4, 4, 1500.95);
Product CalculusBook = new Product("Calculus Book", Shmidt, 1, 10, 35);
Product NoteBooks = new Product("Notebooks", Christy, 3, 120, 25);
Product GPU = new Product("Nvidia 3090 GPU", AnneSophie, 4, 1, 2000);
Product Chair = new Product("Ikea Desk Chair", Mathieu, 5, 2, 105);
Buyer John = new Buyer("John", "Smith", "johnsmith", "[email protected]", "2222 Smith rd", "johnsmith");
Buyer Catherine = new Buyer("Catherine", "Parent", "catpar", "[email protected]", "2222 Smith rd", "catpar");
Buyer Olivier = new Buyer("Olivier", "Lavinge", "ollav", "[email protected]", "2422 College ave", "ollav");
Buyer Marie = new Buyer("Marie", "Desjardins", "mardej", "[email protected]", "2622 rue Madrigal", "mardej");
Buyer Stephane = new Buyer("Stephane", "Ouest", "stephou", "[email protected]", "2822 Alton boul", "stephou");
addReseller(Abby);
addReseller(Shmidt);
addReseller(Christy);
addReseller(AnneSophie);
addReseller(Mathieu);
addBuyer(John);
addBuyer(Catherine);
addBuyer(Olivier);
addBuyer(Marie);
addBuyer(Stephane);
uniShop.products.add(Laptop);
uniShop.products.add(CalculusBook);
uniShop.products.add(NoteBooks);
uniShop.products.add(GPU);
uniShop.products.add(Chair);
Gson gson = new GsonBuilder()
.serializeNulls()
.setPrettyPrinting()
.create();
//Generating json file from UniShop object
gson.toJson(uniShop, new FileWriter("./java/implementation/src/UniShop.json"));
System.out.println(gson.toJson(uniShop));
// uniShop.run();
}
}
要序列化的
UniShopFileWriter...
FileWriter fileWriter = new FileWriter("/path/to/your/file");
gson.toJson(uniShop, fileWriter);
fileWriter.flush();
fileWriter.close();