如何从 JPA 标准中的时间戳列中按日期查找？

我想按日期查找记录。在实体和数据库表中，数据类型是时间戳。我用的是Oracle数据库。

@Entity
public class Request implements Serializable {
  @Id
  private String id;
  @Version
  private long version;
  @Temporal(TemporalType.TIMESTAMP)
  @Column(name = "CREATION_DATE")
  private Date creationDate;

  public Request() {
  }

  public Request(String id, Date creationDate) {
    setId(id);
    setCreationDate(creationDate);
  }

  public String getId() {
    return id;
  }

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

  public long getVersion() {
    return version;
  }

  public void setVersion(long version) {
    this.version = version;
  }

  public Date getCreationDate() {
    return creationDate;
  }

  public void setCreationDate(Date creationDate) {
    this.creationDate = creationDate;
  }
}

在主方法中

public static void main(String[] args) {
    RequestTestCase requestTestCase = new RequestTestCase();
    EntityManager em = Persistence.createEntityManagerFactory("Criteria").createEntityManager();

    em.getTransaction().begin();
    em.persist(new Request("005",new Date()));
    em.getTransaction().commit();

    Query q = em.createQuery("SELECT r FROM Request r WHERE r.creationDate = :creationDate",Request.class);
    q.setParameter("creationDate",new GregorianCalendar(2012,12,5).getTime());
    Request r = (Request)q.getSingleResult();
    System.out.println(r.getCreationDate());        

}

Oracle数据库中的记录是，

ID      CREATION_DATE                   VERSION

006     05-DEC-12 05.34.39.200000 PM    1

例外的是，

Exception in thread "main" javax.persistence.NoResultException: getSingleResult() did     not retrieve any entities.
at    org.eclipse.persistence.internal.jpa.EJBQueryImpl.throwNoResultException(EJBQueryImpl.java:1246)
at org.eclipse.persistence.internal.jpa.EJBQueryImpl.getSingleResult(EJBQueryImpl.java:750)
at com.ktrsn.RequestTestCase.main(RequestTestCase.java:29)

数据库类型是TIMESTAMP并不是DATE，这意味着您存储准确的时间。

使用时new GregorianCalendar(2012,12,5).getTime()您正在查询与给定日期 00:00:00.000 匹配且数据库中不存在的时间戳

您应该更改数据库以存储日期而不是时间戳，或者更改您的查询。

JPA 2 具有年、月和日功能，因此您可以

SELECT WHERE YEAR(yourdate) = YEAR(dbdate) AND MONTH(yourdate) = MONTH(dbdate) and DAY(yourdate) = DATE(dbdate)

在 Criteria API 中，您可以执行以下操作：

Expression<Integer> yourdateYear = cb.function("year", Integer.class, yourdate);
Expression<Integer> yourdateMonth = cb.function("month", Integer.class, yourdate);
Expression<Integer> yourdateDay = cb.function("day", Integer.class, yourdate);

然后将它们与 AND 表达式结合起来，并对 db 中的日期字段执行相同的操作并进行比较。