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问题描述

我在Postgres中的表格下方，并在Spring Boot 2.1.6.RELEASE 中使用 Java 8和Postgres-11 。我已经浏览了链接：

错误类型

LocalDateTime 是错误的类型。该类不能代表片刻，如其Javadoc中所述。

该类故意没有时区或从UTC偏移的概念。因此它代表一个日期和时间，例如 2019年1月23日中午，但不知道在东京，巴黎或蒙特利尔是否是中午，例如，三个非常不同的时刻相距几个小时。因此，此类型适用于标准SQL类型没有时区的时间戳 – 没有，而不是 with 。

有关更多讨论，请参见：

右类型

对于标准SQL类型 TIMESTAMP WITH时区，您应该使用Java类型即时， OffsetDateTime 或 ZonedDateTime 。在这三个版本中，JDBC 4.2仅需要第二个 OffsetDateTime 支持。

检索。

  OffsetDateTime odt = myResultSet.getObject（…，OffsetDateTime.class）；

从Postgres检索的值将始终为UTC。 SQL标准未指定此行为，因此数据库各不相同。在Postgres中，任何发送到 TIMESTAMP WITH TIME ZONE 类型的字段的值都将调整为UTC。检索的值以UTC为单位。

存储。

  myPreparedStatement.setObject（…，odt）;

从UTC（零偏移）调整为特定人群使用的挂钟时间

  ZoneId z = ZoneId.of（ Asia / Tokyo; 
 ZonedDateTime zdt = odt.atZoneSameInstant（z）;

JPA

我不使用JPA，而是希望保持简单。

但是根据，JPA 2.2支持 java.time 类型。

Hibernate也支持 java .time 。

I've below Table in Postgres and using Java 8 and Postgres-11 with Spring Boot 2.1.6.RELEASE. I already went through the link: How to map timestamp column to JPA type? and Hibernate creates column without name when using "default CURRENT_TIMESTAMP on update CURRENT_TIMESTAMP", but I really wanted to use Java 8 Date API and not Java 7.

CREATE TABLE note(
    note_id serial PRIMARY KEY,
    message varchar(255) NOT NULL,
    created_at TIMESTAMP WITH TIME ZONE DEFAULT CURRENT_TIMESTAMP
);

I've created model class like below, but doesn't match with what I need. Any help?

@Data
@Builder
@AllArgsConstructor
@NoArgsConstructor
@EqualsAndHashCode(callSuper = true)
@Entity
public class Note extends AuditEnabledEntity{
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "note_id")
    private int noteId;

    @Column(name = "message")
    private String message;

    @Column(name = "created_at")
    private LocalDateTime createdAt;
}

解决方案

Wrong type

LocalDateTime is the wrong type here. That class cannot represent a moment, as explained in its Javadoc.

That class purposely has no concept of time zone or offset-from-UTC. So it represents a date and a time-of-day such as "noon on the 23rd of January 2019", but don’t know if that is noon in Tokyo, Paris, or Montréal, for a example, three very different moments that are several hours apart. So this type is appropriate for standard SQL type TIMESTAMP WITHOUT TIME ZONE – without, not with.

For more discussion, see: What's the difference between Instant and LocalDateTime?

Right type

For standard SQL type TIMESTAMP WITH TIME ZONE, you should be using the Java types Instant, OffsetDateTime, or ZonedDateTime. Of those three, JDBC 4.2 requires support only for the second, OffsetDateTime.

Retrieval.

OffsetDateTime odt = myResultSet.getObject( … , OffsetDateTime.class ) ;

The value retrieved from Postgres will always be in UTC. The SQL standard does not specify this behavior, so databases vary. In Postgres any value sent to a field of type TIMESTAMP WITH TIME ZONE is adjusted into UTC. Retrieved values are in UTC.

Storing.

myPreparedStatement.setObject( … , odt ) ;

Adjust from UTC (offset of zero) to the wall-clock time used by the people of a particular region (a time zone).

ZoneId z = ZoneId.of( "Asia/Tokyo" ;
ZonedDateTime zdt = odt.atZoneSameInstant( z ) ;

JPA

I don’t use JPA, preferring to keep things simple.

But according to this Answer, JPA 2.2 support the java.time types.

Hibernate as well supports java.time.

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