JPA 无法更新日期

Question

在我的 JavaEE 应用程序中，我使用 JPA 来存储我的数据。 但是我在更新存储在数据库中的日期时遇到了问题。当我想在我的应用程序中更改它时（以及当我合并时），所有字段都在更新，除了日期的... $ 你可以帮帮我吗 ？

这是我的实体：

package persistence
import java.io.Serializable;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.JoinTable;
import javax.persistence.ManyToMany;
import javax.persistence.ManyToOne;
import javax.persistence.OneToMany;
import javax.persistence.OneToOne;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
@Entity
public class Event implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;

@Column(name = "NAME")
private String name;
@Column(name = "PLACE")
private String place;
@Temporal(TemporalType.TIMESTAMP)
@Column(name = "BEGINDATE")
private Date beginDate;
@Temporal(TemporalType.TIMESTAMP)
@Column(name = "ENDDATE")
private Date endDate;
@Column(name = "VISIBILITY")
private int visibility;
@Column(name = "DESCRIPTION")
private String description;

@OneToMany(mappedBy="relatedEvent")
private List<CustomizeEvent> customizedEvents;

@OneToOne(cascade = CascadeType.PERSIST,optional=false)
private Periodicity periodicity;

@ManyToOne(optional=false)
private UserAgenda eventOwner;

@ManyToMany
@JoinTable(name="EVENTS_BELONG_AGENDAS",joinColumns= @JoinColumn(name="EVENT_ID",referencedColumnName="ID"),inverseJoinColumns=@JoinColumn(name="AGENDA_ID",referencedColumnName="ID"))
private List<Agenda> belongToAgendas;

@ManyToMany
@JoinTable(name="EVENTS_GUESTS_AGENDAS",joinColumns= @JoinColumn(name="EVENT_ID",referencedColumnName="ID"),inverseJoinColumns=@JoinColumn(name="AGENDA_ID",referencedColumnName="ID"))    
private List<Agenda> guestToAgendas;

public Event() {
}

public Event(String name, String place, Date beginDate, Date endDate, int visibility, String description, Periodicity periodicity, UserAgenda eventOwner, Agenda agenda) {
    this.name = name;
    this.place = place;
    this.beginDate = beginDate;
    this.endDate = endDate;
    this.visibility = visibility;
    this.description = description;
    this.periodicity = periodicity;
    this.eventOwner = eventOwner;
    this.belongToAgendas = new ArrayList<Agenda>();
    this.belongToAgendas.add(agenda);
    this.customizedEvents = new ArrayList<CustomizeEvent>();
    this.guestToAgendas = new ArrayList<Agenda>();
}

public Event(String name, String place, Date beginDate, Date endDate, int visibility, String description, Periodicity periodicity, UserAgenda eventOwner, Agenda agenda,List<Agenda> guests) {
    this.name = name;
    this.place = place;
    this.beginDate = beginDate;
    this.endDate = endDate;
    this.visibility = visibility;
    this.description = description;
    this.periodicity = periodicity;
    this.eventOwner = eventOwner;
    this.belongToAgendas = new ArrayList<Agenda>();
    this.belongToAgendas.add(agenda);
    this.customizedEvents = new ArrayList<CustomizeEvent>();
    this.guestToAgendas = guests;
}


public Long getId() {
    return id;
}

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

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}

public String getPlace() {
    return place;
}

public void setPlace(String place) {
    this.place = place;
}

public Date getBeginDate() {
    return beginDate;
}

public void setBeginDate(Date beginDate) {
    this.beginDate = beginDate;
}

public Date getEndDate() {
    return endDate;
}

public void setEndDate(Date endDate) {
    this.endDate = endDate;
}

public int getVisibility() {
    return visibility;
}

public void setVisibility(int visibility) {
    this.visibility = visibility;
}

public String getDescription() {
    return description;
}

public void setDescription(String description) {
    this.description = description;
}

public List<CustomizeEvent> getCustomizedEvents() {
    return customizedEvents;
}

public void setCustomizedEvents(List<CustomizeEvent> customizedEvents) {
    this.customizedEvents = customizedEvents;
}

public Periodicity getPeriodicity() {
    return periodicity;
}

public void setPeriodicity(Periodicity periodicity) {
    this.periodicity = periodicity;
}

public UserAgenda getEventOwner() {
    return eventOwner;
}

public void setEventOwner(UserAgenda eventOwner) {
    this.eventOwner = eventOwner;
}

public List<Agenda> getBelongToAgendas() {
    return belongToAgendas;
}

public void setBelongToAgendas(List<Agenda> belongToAgendas) {
    this.belongToAgendas = belongToAgendas;
}

public List<Agenda> getGuestToAgendas() {
    return guestToAgendas;
}

public void setGuestToAgendas(List<Agenda> guestToAgendas) {
    this.guestToAgendas = guestToAgendas;
}





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

@Override
public boolean equals(Object object) {
    // TODO: Warning - this method won't work in the case the id fields are not set
    if (!(object instanceof Event)) {
        return false;
    }
    Event other = (Event) object;
    if ((this.id == null && other.id != null) || (this.id != null && !this.id.equals(other.id))) {
        return false;
    }
    return true;
}

@Override
public String toString() {
    return "persistence.Event[ id=" + id + " ]";
}

}

这是我在托管 bean 中调用的函数：

public void setNewEndDate(Event event, Date endDate) {
    Event e = em.find(Event.class, event.getId());
    e.setEndDate(endDate);
    e.setDescription("New description");
    em.persist(e);
}

Answer 1

如果您尝试更新的列上有updatable=false，问题也是一样的。

Answer 2

首先，最好提供一些有关事务管理的信息，因为它对于 JPA 的行为方式非常重要。

这是我认为会发生的事情：

您已经从 EntityManager 加载了 Event-object，它可能已从 session 中分离出来，因为当您执行 EntityManager#find 时您没有收到错误（您不能有 2 个具有相同 id 的对象一次在 EntityManager 中，你会得到一个异常..) 那么，你改变刚刚加载的附加对象的状态，并将它注册到 EntityManager 中（我不认为持久化的调用是正确的，或者在这里甚至是必要的..）但是，您的分离对象（作为参数发送的对象）仍然存在，并且尚未使用新值进行更新。因此，如果此对象在稍后被重新附加并保存（它可能由您明确执行，或者它可能在事务完成时自动发生），您最终将覆盖相关方法中设置的值。

如果有的话，您在此处提供的方法可能（并且应该）如下所示：

@Transactional
public void setNewDate(final Integer eventId, final Date endDate() {
    final Event e = em.find(Event.class, eventId);
    e.setEndDate(endDate);
    //no need to explicitly save here, the changes will be saved when the transcation ends,
    //and the transaction will only last this method, as indicated by the @Transactional annotation.
}

但是，这仍然不是使用 JPA 的正确方法，通常你有一个存储库层，它处理基本的 CRUD 操作（查找、保存等），而在它之上的一层是逻辑层，它处理对象中值的实际更改。

顺便说一句，你的 equals 和 hashcode 方法违反了这些方法的约定，因为 id 并不总是设置（一个新创建的尚未持久化的事件对象将没有一个 id），以及两个不同的新创建的 Event-尚未存储的对象，因此没有 id（除非你自己设置了 id，你真的不应该这样做），将被 equals 方法认为是相同的。