Calendar object won't update in database but d

问题:

I'm representing Appointments in an entity bean which have a startTime and endTime of type Calendar. This is stored using JPA as TIMESTAMP. If I edit the Appointment object's start / end time it updates on the object itself during the session but it's not updated within the database itself. Other elements such as the Appointment's description successfully update in the database.. It's only he start and end time which are not.

Entity class (this is indirectly updated in the database with EntityManager.merge():

package mcknighte.entity;

import java.io.Serializable;
import java.util.Calendar;
import java.util.List;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.ManyToOne;
import javax.persistence.OneToMany;
import javax.persistence.Temporal;
import static javax.persistence.TemporalType.TIMESTAMP;
import javax.validation.constraints.NotNull;
import mcknighte.common.Convertable;

/**
 * Appointment entity class, to represent an Appointment within the database
 * and throughout the application
 *
 * @author Edward McKnight (UP608985)
 * @see Client
 * @see AppointmentFacade
 * @see AppointmentService
 * @see AppointmentController
 * @since 2017
 * @version 1.0
 */
@Entity
public class Appointment implements Serializable, Convertable {
    private static final long serialVersionUID = 1L;
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;
    @NotNull
    @Temporal(TIMESTAMP)
    private Calendar startTime;
    @NotNull
    @Temporal(TIMESTAMP)
    private Calendar endTime;
    @NotNull
    private String description;
    @NotNull
    @ManyToOne(targetEntity = Client.class)
    private Client creator;
    @NotNull
    @OneToMany(targetEntity = Client.class)
    private List<Client> attendees;

    /**
     * Constructor
     */
    public Appointment() {
        this.startTime = Calendar.getInstance();
        this.endTime = Calendar.getInstance();
    }

    /**
     * Get the attendees for the appointment
     *
     * @return a list of attendees for the appointment
     */
    public List<Client> getAttendees() {
        return attendees;
    }

    /**
     * Set the attendees for the appointment
     *
     * @param attendees a list of attendees for the appointment
     */
    public void setAttendees(List<Client> attendees) {
        this.attendees = attendees;
    }

    /**
     * Get the creator of the appointment
     *
     * @return the creator of the appointment
     */
    public Client getCreator() {
        return creator;
    }

    /**
     * Set the creator of the appointment
     *
     * @param creator the creator of the appointment
     */
    public void setCreator(Client creator) {
        this.creator = creator;
    }

    /**
     * Get the description for the appointment
     *
     * @return the description for the appointment
     */
    public String getDescription() {
        return description;
    }

    /**
     * Set the description for the appointment
     *
     * @param description the description for the appointment
     */
    public void setDescription(String description) {
        this.description = description;
    }

    /**
     * Get the end time of the appointment
     *
     * @return the end time of the appointment
     */
    public Calendar getEndTime() {
        return endTime;
    }

    /**
     * Set the end time of the appointment
     *
     * @param end the end time of the appointment
     */
    public void setEndTime(Calendar end) {
        this.endTime = end;
    }

    /**
     * Get the start time of the appointment
     *
     * @return the start time of the appointment
     */
    public Calendar getStartTime() {
        return startTime;
    }

    /**
     * Set the start time of the appointment
     *
     * @param start the start time of the appointment
     */
    public void setStartTime(Calendar start) {
        this.startTime = start;
    }

    /**
     * Get the ID for the appointment
     *
     * @return the ID for the appointment
     */
    @Override
    public Long getId() {
        return id;
    }

    /**
     * Set the ID for the appointment
     *
     * @param id the ID for the appointment
     */
    public void setId(Long id) {
        this.id = id;
    }

    /**
     * Hash code
     *
     * @return int
     */
    @Override
    public int hashCode() {
        int hash = 0;
        hash += (id != null ? id.hashCode() : 0);
        return hash;
    }

    /**
     * Equals
     *
     * @param object the object to compare to
     * @return whether or not this equals the object being compared to
     */
    @Override
    public boolean equals(Object object) {
        if (!(object instanceof Appointment)) {
            return false;
        }
        Appointment other = (Appointment) object;
        return !((this.id == null && other.id != null) || (this.id != null && !this.id.equals(other.id)));
    }

    /**
     * Represent this object as a string
     * 
     * @return a string representation of this object
     */
    @Override
    public String toString() {
        return "mcknighte.entity.Appointment[ id=" + id + " ]";
    }

}

回答1:

The issue has been resolved after finding another StackOverflow question and reading the Oracle documentation.

All that needed to be done was to add an @Mutable annotation to each of the Calendar properties, as Date and Calendar are immutable by default.