实体属性更改后网格不更新

Question

在我的项目中，我有“事件”和“用户”。用户报名参加活动。无论如何，事件实体有一个“参与者”属性，它是一个 int 值，表示事件的总容量，每次用户注册事件时都会递减。每个事件还有一个名为“注册者”的 ArrayList 属性，该属性应该包含已注册该事件的所有当前用户实体。

我的问题是，当用户注册活动时，这个容量属性“参与者”根本没有像预期的那样减少，我怀疑这意味着 ArrayList“注册者”也不会随着注册的用户而更新。在使用用户注册事件后，我重新检查 EventManagementView，以查看容量是否从其初始设置值下降，但它从来没有下降。以下是直接用于此问题的所有代码：

事件实体的 Events.java 类：

package ymca.tracker.application.data.entity;

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;
    // The capacity attribute I was referring to above
    public int participants;
    private String nonMemberPrice;
    private String memberPrice;
    private String location;
    private String description;
    // Registrants ArrayList that is supposed to hold all the User entities that sign up for an event
    @ElementCollection
    @OneToMany(fetch = FetchType.EAGER)
    public 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, ArrayList<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.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;
    }
    // This method is called (only with value 1 for now) to decrease participants count
    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 List<User> getRegistrants() {
        return registrants;
    }
    public void setGuests(ArrayList<User> registrants) {
        this.registrants = registrants;
    }
    // This method is called to add a User to the registrants ArrayList
    public void addRegistrant(User user) {
        this.registrants.add(user);
    }
    public void removeRegistrant(User user) {
        this.registrants.remove(user);
    }
}

用户实体的 User.java 类：

package ymca.tracker.application.data.entity;

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;
    }
}

我的员工/管理员帐户使用下面的这个 EventManagementView 来初始创建事件：

package ymca.tracker.application.views.eventmanagement;

import com.vaadin.flow.component.Component;
import com.vaadin.flow.component.HasStyle;
import com.vaadin.flow.component.UI;
import com.vaadin.flow.component.button.Button;
import com.vaadin.flow.component.button.ButtonVariant;
import com.vaadin.flow.component.datepicker.DatePicker;
import com.vaadin.flow.component.dependency.Uses;
import com.vaadin.flow.component.formlayout.FormLayout;
import com.vaadin.flow.component.grid.Grid;
import com.vaadin.flow.component.grid.GridVariant;
import com.vaadin.flow.component.html.Div;
import com.vaadin.flow.component.icon.Icon;
import com.vaadin.flow.component.notification.Notification;
import com.vaadin.flow.component.orderedlayout.HorizontalLayout;
import com.vaadin.flow.component.splitlayout.SplitLayout;
import com.vaadin.flow.component.textfield.IntegerField;
import com.vaadin.flow.component.textfield.TextField;
import com.vaadin.flow.component.timepicker.TimePicker;
import com.vaadin.flow.data.binder.BeanValidationBinder;
import com.vaadin.flow.data.binder.ValidationException;
import com.vaadin.flow.router.BeforeEnterEvent;
import com.vaadin.flow.router.BeforeEnterObserver;
import com.vaadin.flow.router.PageTitle;
import com.vaadin.flow.router.Route;
import com.vaadin.flow.spring.data.VaadinSpringDataHelpers;

import java.time.Duration;
import java.util.ArrayList;
import java.util.List;
import java.util.Optional;
import java.util.UUID;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.domain.PageRequest;

import ymca.tracker.application.data.entity.Events;
import ymca.tracker.application.data.entity.User;
import ymca.tracker.application.data.service.EventsService;

@PageTitle("Event Management")
@Route(value = "event-management")
@Uses(Icon.class)
public class EventManagementView extends Div implements BeforeEnterObserver {

    private final String EVENTS_ID = "eventsID";
    private final String EVENTS_EDIT_ROUTE_TEMPLATE = "event-management/%s/edit";

    private Grid<Events> grid = new Grid<>(Events.class, false);

    private TextField name;
    private DatePicker startDate;
    private DatePicker endDate;
    private TimePicker startTime;
    private TimePicker endTime;
    private TextField recurring;
    private IntegerField participants;
    private TextField nonMemberPrice;
    private TextField memberPrice;
    private TextField location;
    private TextField description;
    
    private Button delete = new Button("Delete");
    private Button cancel = new Button("Cancel");
    private Button save = new Button("Save");

    private BeanValidationBinder<Events> binder;

    private Events events;

    private EventsService eventsService;

    public EventManagementView(@Autowired EventsService eventsService) {
        this.eventsService = eventsService;
        addClassNames("event-management-view", "flex", "flex-col", "h-full");

        // Create UI
        SplitLayout splitLayout = new SplitLayout();
        splitLayout.setSizeFull();

        createGridLayout(splitLayout);
        createEditorLayout(splitLayout);

        add(splitLayout);

        // Configure Grid
        grid.addColumn("name").setAutoWidth(true);
        grid.addColumn("startDate").setAutoWidth(true);
        grid.addColumn("endDate").setAutoWidth(true);
        grid.addColumn("startTime").setAutoWidth(true);
        grid.addColumn("endTime").setAutoWidth(true);
        grid.addColumn("recurring").setAutoWidth(true);
        grid.addColumn("participants").setAutoWidth(true);
        grid.addColumn("nonMemberPrice").setAutoWidth(true);
        grid.addColumn("memberPrice").setAutoWidth(true);
        grid.addColumn("location").setAutoWidth(true);
        grid.addColumn("description").setAutoWidth(true);

        grid.setItems(query -> eventsService.list(
                PageRequest.of(query.getPage(), query.getPageSize(), VaadinSpringDataHelpers.toSpringDataSort(query)))
                .stream());
        
        grid.addThemeVariants(GridVariant.LUMO_NO_BORDER);
        grid.setHeightFull();

        // when a row is selected or deselected, populate form
        grid.asSingleSelect().addValueChangeListener(event -> {
            if (event.getValue() != null) {
                UI.getCurrent().navigate(String.format(EVENTS_EDIT_ROUTE_TEMPLATE, event.getValue().getId()));
            } else {
                clearForm();
                UI.getCurrent().navigate(EventManagementView.class);
            }
        });

        // Configure Form
        binder = new BeanValidationBinder<>(Events.class);

        // Bind fields. This is where you'd define e.g. validation rules

        binder.bindInstanceFields(this);

        delete.addClickListener(e -> {
            binder.removeBean();

            eventsService.delete(this.events.getId());
            eventsService.update(this.events);
            clearForm();
            refreshGrid();
            Notification.show("Event deleted");
            UI.getCurrent().navigate(EventManagementView.class);
        });

        cancel.addClickListener(e -> {
            clearForm();
            refreshGrid();
        });

        save.addClickListener(e -> {
            try {
                if (this.events == null) {
                    this.events = new Events();
                }
                /* 
                    Since the ArrayList isn't set by the grid editor, I hardcoded an 
                    empty ArrayList to go with the new Event here
                */
                ArrayList<User> registrants = new ArrayList<User>();
                this.events.setGuests(registrants);
                binder.writeBean(this.events);

                eventsService.update(this.events);
                clearForm();
                refreshGrid();
                Notification.show("Event details saved.");
                UI.getCurrent().navigate(EventManagementView.class);
            } catch (ValidationException validationException) {
                Notification.show("An exception happened while trying to save the event details.");
            }
        });

    }

    @Override
    public void beforeEnter(BeforeEnterEvent event) {
        Optional<UUID> eventsId = event.getRouteParameters().get(EVENTS_ID).map(UUID::fromString);
        if (eventsId.isPresent()) {
            Optional<Events> eventsFromBackend = eventsService.get(eventsId.get());
            if (eventsFromBackend.isPresent()) {
                populateForm(eventsFromBackend.get());
            } else {
                Notification.show(
                        String.format("The requested event was not found, ID = %s", eventsId.get()), 3000,
                        Notification.Position.BOTTOM_START);
                // when a row is selected but the data is no longer available,
                // refresh grid
                refreshGrid();
                event.forwardTo(EventManagementView.class);
            }
        }
    }

    private void createEditorLayout(SplitLayout splitLayout) {
        Div editorLayoutDiv = new Div();
        editorLayoutDiv.setClassName("flex flex-col");
        editorLayoutDiv.setWidth("400px");

        Div editorDiv = new Div();
        editorDiv.setClassName("p-l flex-grow");
        editorLayoutDiv.add(editorDiv);

        FormLayout formLayout = new FormLayout();
        name = new TextField("Event Name");
        startDate = new DatePicker("Start Date");
        endDate = new DatePicker("End Date");
        startTime = new TimePicker("Start Time");
        startTime.setStep(Duration.ofMinutes(10));
        endTime = new TimePicker("End Time");
        endTime.setStep(Duration.ofMinutes(10));
        recurring = new TextField("Recurring Event?");
        participants = new IntegerField("Number of Participants");
        nonMemberPrice = new TextField("Non-Member Price");
        memberPrice = new TextField("Member Price");
        location = new TextField("Location");
        description = new TextField("Description");
        Component[] fields = new Component[]{name, startDate, endDate, startTime, endTime, recurring, participants, nonMemberPrice, memberPrice, location, description};

        for (Component field : fields) {
            ((HasStyle) field).addClassName("full-width");
        }
        formLayout.add(fields);
        editorDiv.add(formLayout);
        createButtonLayout(editorLayoutDiv);

        splitLayout.addToSecondary(editorLayoutDiv);
    }

    private void createButtonLayout(Div editorLayoutDiv) {
        HorizontalLayout buttonLayout = new HorizontalLayout();
        buttonLayout.setClassName("w-full flex-wrap bg-contrast-5 py-s px-l");
        buttonLayout.setSpacing(true);
        cancel.addThemeVariants(ButtonVariant.LUMO_TERTIARY);
        save.addThemeVariants(ButtonVariant.LUMO_PRIMARY);
        delete.addThemeVariants(ButtonVariant.LUMO_ERROR);
        buttonLayout.add(save, cancel, delete);
        editorLayoutDiv.add(buttonLayout);
    }

    private void createGridLayout(SplitLayout splitLayout) {
        Div wrapper = new Div();
        wrapper.setId("grid-wrapper");
        wrapper.setWidthFull();
        splitLayout.addToPrimary(wrapper);
        wrapper.add(grid);
    }

    private void refreshGrid() {
        grid.select(null);
        grid.getLazyDataView().refreshAll();
    }

    private void clearForm() {
        populateForm(null);
    }

    private void populateForm(Events value) {
        this.events = value;
        binder.readBean(this.events);

    }
} 

处理事件的代码部分注册一个用户（如果您希望查看此视图​​的整个类而不仅仅是此方法，请告诉我）：

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.addRegistrant(guest);; // Adds guest sign-up info to events guest list
                    selectedEvent.decreaseCapacity(1); // Decrease events participants count by 1
                    
                    signUpForm.close();
                    Notification.show("Registered 1 Guest", 5000, Position.TOP_CENTER);
                }                
            } else {
                Notification.show("Please complete the form to register", 5000, Position.TOP_CENTER);
            }
        });