JPA 实体、Oracle 10g 和日历类型属性是否存在问题？
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Is there a Problem with JPA Entities, Oracle 10g and Calendar Type properties?
提问by huo73
I'm experiencing the following very annoying behaviour when using JPA entitys in conjunction with Oracle 10g.
将 JPA 实体与 Oracle 10g 结合使用时，我遇到了以下非常烦人的行为。
Suppose you have the following entity.
假设您有以下实体。
@Entity
@Table(name = "T_Order")
public class TOrder implements Serializable {
private static final long serialVersionUID = 2235742302377173533L;
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Integer id;
@Column(name = "activationDate")
private Calendar activationDate;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public Calendar getActivationDate() {
return activationDate;
}
public void setActivationDate(Calendar activationDate) {
this.activationDate = activationDate;
}
}
This entity is mapped to Oracle 10g, so in the DB there will be a table T_ORDERwith a primary key NUMBERcolumn IDand a TIMESTAMPcolumn activationDate.
此实体映射到 Oracle 10g，因此在 DB 中将有一个表，T_ORDER其中包含一个主键NUMBERcolumnID和一个TIMESTAMPcolumn activationDate。
Lets suppose I create an instance of this class with the activation date 15. Sep 2008 00:00AM. My local timezone is CEST which is GMT+02:00. When I persist this object and select the data from the table T_ORDERusing sqlplus, I find out that in the table actually 14. Sep 2008 22:00is stored, which is ok so far, because the oracle db timezone is GMT.
假设我用激活日期创建了这个类的一个实例15. Sep 2008 00:00AM。我当地的时区是 CEST，即GMT+02:00. 当我持久化这个对象并T_ORDER使用sqlplus从表中选择数据时，我发现实际上14. Sep 2008 22:00存储在表中，到目前为止还可以，因为oracle db时区是GMT。
But now the annoying part. When I read this entity back into my JAVA program, I find out that the oracle time zone is ignored and I get 14. Sep 2008 22:00 CEST, which is definitly wrong.
但现在是烦人的部分。当我将这个实体读回我的 JAVA 程序时，我发现 oracle 时区被忽略了，我得到14. Sep 2008 22:00 CEST，这绝对是错误的。
So basically, when writing to the DB the timezone information will be used, when reading it will be ignored.
所以基本上，当写入数据库时，时区信息将被使用，读取时将被忽略。
Is there any solution for this out there? The most simple solution I guess would be to set the oracle dbs timezone to GMT+02, but unfortunatly I can't do this because there are other applications using the same server.
有什么解决方案吗？我想最简单的解决方案是将 oracle dbs 时区设置为GMT+02，但不幸的是我不能这样做，因为还有其他应用程序使用相同的服务器。
We use the following technology
我们使用以下技术
MyEclipse 6.5 JPA with Hibernate 3.2 Oracle 10g thin JDBC Driver
MyEclipse 6.5 JPA 与 Hibernate 3.2 Oracle 10g 瘦 JDBC 驱动程序
采纳答案by davetron5000
You should not use a Calendar for accessing dates from the database, for this exact reason. You should use java.util.Dateas so:
出于这个确切原因，您不应该使用日历来访问数据库中的日期。你应该这样使用java.util.Date：
@Temporal(TemporalType.TIMESTAMP)
@Column(name="activationDate")
public Date getActivationDate() {
return this.activationDate;
}
java.util.Datepoints to a moment in time, irrespective of any timezones. Calendar can be used to format a date for a particular timezone or locale.
java.util.Date指向某个时刻，与任何时区无关。日历可用于格式化特定时区或语言环境的日期。
回答by Jeroen Wyseur
I already had my share of problems with JPA and timestamps. I've been reading in the oracle forumsand please check the following:
我已经遇到了 JPA 和时间戳的问题。我一直在阅读oracle 论坛，请检查以下内容：
- The field in the database should be TIMESTAMP_TZ and not just TIMESTAMP
- Try adding the annotation @Temporal(value = TemporalType.TIMESTAMP)
- If you don't really need the timezone, put in a date or timestamp field.
- 数据库中的字段应该是 TIMESTAMP_TZ 而不仅仅是 TIMESTAMP
- 尝试添加注释 @Temporal(value = TemporalType.TIMESTAMP)
- 如果您真的不需要时区，请输入日期或时间戳字段。
