JPA存储库保存方法创建新实例，而不是合并

Question

在我的项目中，有一些用户注册的活动。当用户注册事件时，事件容量会减少 1，并且用户名将添加到事件的 String 属性中。在我的代码中对事件进行这些更改后，我调用 eventsRepository.save(event)，我认为这只是合并了新更新的事件，但由于某种原因，我的数据库只是创建了一个全新的事件具有新 ID 和新值的事件。

以下是该问题的一些图片：

用户注册之前的事件数据（包括存储库中的 UUID）

用户注册后的事件数据

用户代码：

import javax.persistence.Embeddable;
import javax.persistence.Entity;

import org.apache.commons.codec.digest.DigestUtils;
import org.apache.commons.lang3.RandomStringUtils;

import ymca.tracker.application.data.AbstractEntity;

@Embeddable
@Entity
public class User extends AbstractEntity {

    private boolean familyAccount;
    private String firstName;
    private String lastName;
    private String username;
    private String password;
    private String passwordSalt;
    private String passwordHash;
    private ymca.tracker.application.data.entity.Role role; 

    public User() {
        
    }

    public User(boolean familyAccount, String firstName, String lastName, 
        String username, String password, ymca.tracker.application.data.entity.Role role) {
        this.familyAccount = familyAccount;
        this.firstName = firstName;
        this.lastName = lastName;
        this.username = username;
        this.role = role;
        this.password = password;
        this.passwordSalt = RandomStringUtils.random(32);
        this.passwordHash = DigestUtils.sha1Hex(password + passwordSalt);
    }

    public boolean checkPassword(String password) {
        return DigestUtils.sha1Hex(password + passwordSalt).equals(passwordHash);
    }
    public boolean getFamilyAccount() {
        return familyAccount;
    }
    public void setFamilyAccount(boolean familyAccount) {
        this.familyAccount = familyAccount;
    }
    public String getFirstName() {
        return firstName;
    }
    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }
    public String getLastName() {
        return lastName;
    }
    public void setLastName(String lastName) {
        this.lastName = lastName;
    }
    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 getPasswordSalt() {
        return passwordSalt;
    }
    public void setPasswordSalt(String passwordSalt) {
        this.passwordSalt = passwordSalt;
    }
    public String getPasswordHash() {
        return passwordHash;
    }
    public void setPasswordHash(String passwordHash) {
        this.passwordHash = passwordHash;
    }
    public ymca.tracker.application.data.entity.Role getRole() {
        return role;
    }
    public void setRole(ymca.tracker.application.data.entity.Role role) {
        this.role = role;
    }
}

事件代码：

import java.time.LocalDate;
import java.time.LocalTime;
import java.util.ArrayList;
import java.util.List;

import javax.persistence.ElementCollection;
import javax.persistence.Embeddable;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.OneToMany;

import ymca.tracker.application.data.AbstractEntity;

@Embeddable
@Entity
public class Events extends AbstractEntity {

    private String name;
    private java.time.LocalDate startDate;
    private java.time.LocalDate endDate;
    private java.time.LocalTime startTime;
    private java.time.LocalTime endTime;
    private String recurring;
    private int participants;
    private String nonMemberPrice;
    private String memberPrice;
    private String location;
    private String description;
    private String users;
    // Not currently used
    @ElementCollection
    @OneToMany(fetch = FetchType.LAZY)
    private List<User> registrants = new ArrayList<User>();

    public Events() {

    }

    public Events(String name, LocalDate startDate, LocalDate endDate, LocalTime startTime, LocalTime endTime, 
        String recurring, int participants, String nonMemberPrice, String memberPrice, String location, 
            String description, String users, List<User> registrants) {
            this.name = name;
            this.startDate = startDate;
            this.endDate = endDate;
            this.startTime = startTime;
            this.endTime = endTime;
            this.recurring = recurring;
            this.participants = participants;
            this.nonMemberPrice = nonMemberPrice;
            this.memberPrice = memberPrice;
            this.location = location;
            this.description = description;
            this.users = " ";
            this.registrants = registrants;
        }

    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public java.time.LocalDate getStartDate() {
        return startDate;
    }
    public void setStartDate(java.time.LocalDate startDate) {
        this.startDate = startDate;
    }
    public java.time.LocalDate getEndDate() {
        return endDate;
    }
    public void setEndDate(java.time.LocalDate endDate) {
        this.endDate = endDate;
    }
    public java.time.LocalTime getStartTime() {
        return startTime;
    }
    public void setStartTime(java.time.LocalTime startTime) {
        this.startTime = startTime;
    }
    public java.time.LocalTime getEndTime() {
        return endTime;
    }
    public void setEndTime(java.time.LocalTime endTime) {
        this.endTime = endTime;
    }
    public String getRecurring() {
        return recurring;
    }
    public void setRecurring(String recurring) {
        this.recurring = recurring;
    }
    public int getParticipants() {
        return participants;
    }
    public void setParticipants(int participants) {
        this.participants = participants;
    }
    public void decreaseCapacity(int numToDecreaseBy) {
        this.participants = this.participants - numToDecreaseBy;
    }
    public String getMemberPrice() {
        return memberPrice;
    }
    public void setMemberPrice(String memberPrice) {
        this.memberPrice = memberPrice;
    }
    public String getNonMemberPrice() {
        return nonMemberPrice;
    }
    public void setNonMemberPrice(String nonMemberPrice) {
        this.nonMemberPrice = nonMemberPrice;
    }
    public String getLocation() {
        return location;
    }
    public void setLocation(String location) {
        this.location = location;
    }
    public String getDescription() {
        return description;
    }
    public void setDescription(String description) {
        this.description = description;
    }
    public String getUsers() {
        return users;
    }
    public void setUsers(String users) {
        this.users = users;
    }
    public void addUser(String user) {
        this.users = this.users + user + "\n";
    }
    public List<User> getRegistrants() {
        return registrants;
    }
    public void setGuests(ArrayList<User> registrants) {
        this.registrants = registrants;
    }
    public void addRegistrant(User user) {
        this.registrants.add(user);
    }
    public void removeRegistrant(User user) {
        this.registrants.remove(user);
    }
    public boolean checkRegistrant(User user) {
        return this.registrants.contains(user);
    }
}

访客用户注册的代码位于此视图中（保存调用用注释标记）（使用 id 列代码更新）：

import com.vaadin.flow.component.button.Button;
import com.vaadin.flow.component.button.ButtonVariant;
import com.vaadin.flow.component.dialog.Dialog;
import com.vaadin.flow.component.grid.Grid;
import com.vaadin.flow.component.grid.Grid.SelectionMode;
import com.vaadin.flow.component.grid.GridVariant;
import com.vaadin.flow.component.grid.dataview.GridListDataView;
import com.vaadin.flow.component.html.Div;
import com.vaadin.flow.component.html.H2;
import com.vaadin.flow.component.notification.Notification;
import com.vaadin.flow.component.notification.Notification.Position;
import com.vaadin.flow.component.orderedlayout.HorizontalLayout;
import com.vaadin.flow.component.orderedlayout.VerticalLayout;
import com.vaadin.flow.component.orderedlayout.FlexComponent.Alignment;
import com.vaadin.flow.component.textfield.TextField;
import com.vaadin.flow.router.PageTitle;
import com.vaadin.flow.router.Route;

import java.util.ArrayList;
import java.util.List;
import java.util.Set;
import java.util.UUID;

import ymca.tracker.application.data.entity.Events;
import ymca.tracker.application.data.entity.Role;
import ymca.tracker.application.data.entity.User;
import ymca.tracker.application.data.service.EventsRepository;
import ymca.tracker.application.data.service.EventsService;
import ymca.tracker.application.data.service.UserRepository;
import ymca.tracker.application.views.MainLayout;

@PageTitle("Guest Events")
@Route(value = "guest-events", layout = MainLayout.class)
public class GuestEventsView extends Div { 

    private EventsService eventsService;
    private EventsRepository eventsRepository;
    private UserRepository userRepository;

    private Grid<Events> grid;
    private GridListDataView<Events> gridListDataView;

    private Grid.Column<Events> idColumn;
    private Grid.Column<Events> signUpColumn;
    private Grid.Column<Events> nameColumn;
    private Grid.Column<Events> startDateColumn;
    private Grid.Column<Events> endDateColumn;
    private Grid.Column<Events> startTimeColumn;
    private Grid.Column<Events> endTimeColumn;
    private Grid.Column<Events> recurringColumn;
    private Grid.Column<Events> participantsColumn;
    private Grid.Column<Events> priceColumn;
    private Grid.Column<Events> locationColumn;
    private Grid.Column<Events> descriptionColumn;

    public GuestEventsView(EventsService eventsService, EventsRepository eventsRepository, UserRepository userRepository) {
        this.eventsService = eventsService;
        this.eventsRepository = eventsRepository;
        this.userRepository = userRepository;
        addClassName("guest-events-view");
        setSizeFull();
        Button signUpButton = createSignUpButton();
        add(signUpButton);
        createGrid();
        add(grid);
    }

    private void createGrid() {
        createGridComponent();
        addColumnsToGrid();
    }

    private void createGridComponent() {
        grid = new Grid<>();
        grid.setSelectionMode(SelectionMode.SINGLE);
        grid.addThemeVariants(GridVariant.LUMO_NO_BORDER, GridVariant.LUMO_COLUMN_BORDERS);
        grid.setHeight("100%");

        List<Events> events = getEvents();
        gridListDataView = grid.setItems(events);
    }

    private void addColumnsToGrid() {
        createIdColumn();
        createNameColumn();
        createStartDateColumn();
        createEndDateColumn();
        createStartTimeColumn();
        createEndTimeColumn();
        createRecurringColumn();
        createParticipantsColumn();
        createPriceColumn();
        createLocationColumn();
        createDescriptionColumn();
    }

    private Button createSignUpButton() {
        // Create the Dialog object which will be the signUpForm
        Dialog signUpForm = new Dialog();
        // Create the layout for the signUpForm, passing in the Dialog and selected Event
        VerticalLayout signUpFormLayout = createSignUpFormLayout(signUpForm);
        // Add the created layout to the signUpForm
        signUpForm.add(signUpFormLayout);
        // Only the signUpForm can be interacted with when it appears on the screen
        signUpForm.setModal(true);

        Button signUpButton = new Button("Sign Up");
        signUpButton.addClickListener(e -> signUpForm.open());
        return signUpButton;
    }

    private VerticalLayout createSignUpFormLayout(Dialog signUpForm) {
        signUpForm.getElement().setAttribute("aria-label", "Registration Form");

        TextField firstName = new TextField("First Name");
        TextField lastName = new TextField("Last Name");

        H2 headline = new H2("Registration Form");
        headline.getStyle().set("margin-top", "0");

        Button cancel = new Button("Cancel", e -> signUpForm.close());
        Button submit = new Button("Submit", e -> {
            if(fillChecker(firstName.getValue(), lastName.getValue()) == true) {
                String fn = firstName.getValue();
                String ln = lastName.getValue();
                User guest = new User(false, fn, ln,
                    "null", "null", Role.GUEST);

                Set<Events> selected = grid.getSelectedItems();
                Events[] curEvent = selected.toArray(new Events[1]);
                Events selectedEvent = curEvent[0];

                if(selectedEvent == null) {
                    Notification.show("No Event Selected!", 5000, Position.TOP_CENTER);
                } else {
                    userRepository.save(guest); // Saves guest sign-up info to user repository
                    selectedEvent.addUser(fn + " " + ln);
                    selectedEvent.decreaseCapacity(1); // Decrease events participants count by 1
                    
                    // ISSUE HERE
                    // Currently saves new version of event instead of merging
                    UUID toDelete = selectedEvent.getId();
                    eventsRepository.save(selectedEvent);
                    eventsRepository.deleteById(toDelete);

                    signUpForm.close();

                    Notification.show("Registered 1 Guest", 5000, Position.TOP_CENTER);
                }                
            } else {
                Notification.show("Please complete the form to register", 5000, Position.TOP_CENTER);
            }
        });

        submit.addThemeVariants(ButtonVariant.LUMO_PRIMARY);
        HorizontalLayout buttonLayout = new HorizontalLayout(cancel, submit);
        buttonLayout.setAlignItems(Alignment.END);
        buttonLayout.getStyle().set("margin-top", "var(--lumo-space-m");
        VerticalLayout signUpFormLayout = new VerticalLayout(headline, firstName, lastName, buttonLayout);
        signUpFormLayout.setPadding(false);
        signUpFormLayout.setSpacing(false);
        signUpFormLayout.setAlignItems(Alignment.STRETCH);
        signUpFormLayout.getStyle().set("width", "18rem").set("max-width", "100%");

        return signUpFormLayout;
    }

    private boolean fillChecker(String firstName, String lastName) {
        if(firstName.equals("") || lastName.equals("")) {
            return false;
        }
        return true;
    }

    private void createIdColumn() {
        idColumn = grid.addColumn(Events::getId, "id").setHeader("ID").setAutoWidth(true);
    }

    private void createNameColumn() {
        nameColumn = grid.addColumn(Events::getName, "name").setHeader("Name").setAutoWidth(true);
    }

    private void createStartDateColumn() {
        startDateColumn = grid.addColumn(Events::getStartDate, "startDate").setHeader("Start Date").setAutoWidth(true);
    }

    private void createEndDateColumn() {
        startDateColumn = grid.addColumn(Events::getEndDate, "endDate").setHeader("End Date").setAutoWidth(true);
    }

    private void createStartTimeColumn() {
        startTimeColumn = grid.addColumn(Events::getStartTime, "startTime").setHeader("Start Time").setAutoWidth(true);
    }

    private void createEndTimeColumn() {
        startDateColumn = grid.addColumn(Events::getEndTime, "endTime").setHeader("End Time").setAutoWidth(true);
    }

    private void createRecurringColumn() {
        recurringColumn = grid.addColumn(Events::getRecurring, "recurring").setHeader("Recurring?").setAutoWidth(true);
    }

    private void createParticipantsColumn() {
        participantsColumn = grid.addColumn(Events::getParticipants, "participants").setHeader("Capacity").setAutoWidth(true);
    }

    private void createPriceColumn() {
        priceColumn = grid.addColumn(Events::getNonMemberPrice, "price").setHeader("Price").setAutoWidth(true);
    }

    private void createLocationColumn() {
        locationColumn = grid.addColumn(Events::getLocation, "location").setHeader("Location").setAutoWidth(true);
    }

    private void createDescriptionColumn() {
        descriptionColumn = grid.addColumn(Events::getDescription, "description").setHeader("Description").setAutoWidth(true);
    }

    private List<Events> getEvents() {
        List<Events> list = eventsService.findAllEvents();
        List<Events> toReturn = new ArrayList<Events>();
        Events e;
        int size = list.size();
        for(int i = 0; i < size; i++) {
            Events temp = list.get(i);
            e = createEvents(temp.getName(), temp.getStartDate(), temp.getEndDate(), temp.getStartTime(), temp.getEndTime(),
                temp.getRecurring(), temp.getParticipants(), temp.getNonMemberPrice(), temp.getLocation(), temp.getDescription());
            toReturn.add(e);
        }
        return toReturn;
    }

    private Events createEvents(String name, java.time.LocalDate startDate, java.time.LocalDate endDate, 
        java.time.LocalTime startTime, java.time.LocalTime endTime, String recurring, int participants, 
            String price, String location, String description) {

        Events e = new Events();
        e.setName(name);
        e.setStartDate(startDate);
        e.setEndDate(endDate);
        e.setStartTime(startTime);
        e.setEndTime(endTime);
        e.setRecurring(recurring);
        e.setParticipants(participants);
        e.setNonMemberPrice(price);
        e.setLocation(location);
        e.setDescription(description);

        return e;

    }
};

这是我的 AbstractEntity 类：

import java.util.UUID;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.MappedSuperclass;

@MappedSuperclass
public abstract class AbstractEntity {

    @Id
    @GeneratedValue
    private UUID id;

    public UUID getId() {
        return id;
    }

    public void setId(UUID id) {
        this.id = id;
    }

    @Override
    public int hashCode() {
        if (id != null) {
            return id.hashCode();
        }
        return super.hashCode();
    }

    @Override
    public boolean equals(Object obj) {
        if (!(obj instanceof AbstractEntity)) {
            return false; // null or other class
        }
        AbstractEntity other = (AbstractEntity) obj;

        if (id != null) {
            return id.equals(other.id);
        }
        return super.equals(other);
    }
}

添加结果注册网格的 Id 列：

Answer 1

抽象性包含什么？我猜想您缺少有关事件的唯一标识符上的@ID注释，或者在将实体保存到数据库之前没有映射并丢失。没有ID JPA，就无法知道这是一个更新的实体，而不是新的实体。

调试代码并检查该实体是否在此行中包含正确的ID：

eventsRepository.save(selectedEvent)