JPA不能更新日期

Question

在我的JavaEE应用程序中，我使用JPA来存储数据。但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，(当我合并时)，除日期字段外，所有字段都在更新...$你能帮我吗？

下面是我的实体：

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 + " ]";
}

}

下面是我在托管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

如果您在尝试更新的列上具有updatable=false，则问题是相同的。

Answer 2

首先，有一些关于事务管理的信息会很好，因为这对于JPA的行为非常重要。

以下是我认为会发生的事情：

您已经从EntityManager加载了Event-object，并且它可能已从会话中分离，因为在执行EntityManager#find操作时不会出现错误( EntityManager中不能同时有两个具有相同id的对象，否则会出现异常。)然后，更改刚刚加载的附加对象的状态，并在EntityManager中注册它(我认为对persist的调用是不正确的，在这里甚至是不必要的。)但是，您分离的对象(作为参数发送的对象)仍然是活动的，并且没有使用新值进行更新。因此，如果该对象在以后被重新附加并保存(可能是由您显式执行，也可能在事务处理完成时自动发生)，您最终将覆盖在相关方法中设置的值。

您在这里提供的方法可能(也应该)看起来像这样：

@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的正确方式，通常您有一个Repository层，它处理基本的CRUD操作(查找、保存等)，而逻辑层在该层之上，它处理对对象中的值的实际更改。

顺便说一句，你的equals和hashcode方法破坏了这些方法的约定，因为id并不总是被设置的(一个新创建的事件对象没有id)，并且两个不同的，新创建的事件对象还没有被存储，因此没有id (除非你自己设置id，你确实不应该这样做)，equals方法会认为它们是相同的。