英文:

Spring Boot Wrong date returned

问题

我有一个实体类Person
```java
@Entity
@Data
public class Person {

  @Temporal(TemporalType.DATE)
  private Calendar dob;
}

还有一些DAO类

@Data
public class PersonResponse {

  @JsonFormat(pattern = "yyyy-MM-dd")
  private Calendar dob;
}

@Data
public class PersonRequest {
  @DateTimeFormat(pattern = "yyyy-MM-dd")
  private Calendar dob;
}

在存储数值时，它可以完美工作。例如，如果我发送"2000-01-01"，它会按原样存储在数据库中，即"2000-01-01"。但是当我尝试返回它时，我得到的是"1999-12-31"。

现在很明显这是一个时区问题，但我不知道该如何修复它。

我对原因的解释

用户的时区是GMT+1，所以它以某种方式被检索为"2000-01-01T00:00:00.000 +01:00"，然后被解析为UTC"1999-12-31T23:00:00.000 +00:00"，最后返回为"1999-12-31"。

但是为什么？我该如何防止这种情况发生，考虑到用户的时区可能会更改（因此手动添加1小时的时间偏移量不起作用）。

我还尝试将类型从Calendar更改为java.util.Date和java.sql.Date...但没有结果。

类似的问题以前也被提出过，比如这个问题，但我仍然无法理解如何解决它。

<details>
<summary>英文:</summary>

I have an entity Person

@Entity
@Data
public class Person {

@Temporal(TemporalType.DATE)
private Calendar dob;
}

And some dao classes

@Data
public class PersonResponse {

@JsonFormat(pattern = "yyyy-MM-dd")
private Calendar dob;
}

@Data
public class PersonRequest{
@DateTimeFormat(pattern = "yyyy-MM-dd")
private Calendar dob;
}

When storing values it works perfectly. Example if I send "2000-01-01" it's stored as is in the database "2000-01-01". But When I try to return it I get "1999-12-31".

Now it's clear that is a ***Timezone Problem*** but I don't know how to fix it.
##### My explanation for the cause
The user timezone is GMT+1 so it is some how retrieved as "2000-01-01T00:00:00.000 +01:00", then parsed to UTC "1999-12-31T23:00:00.000 +00:00" to finally be returned as "1999-12-31".

But why? And how can I prevent this knowing that users timezones can change (so adding the time offset manually of 1 hour won't work).

I tried also changing type from Calendar to java.util.Date and java.sql.Date... but no result.

Similar questions where asked before like [this one](https://stackoverflow.com/questions/50829014/spring-bootreturn-wrong-value-date-in-json-response) but I still couldn't understand how to fix it

</details>


# 答案1
**得分**: 2

如果适用的话，尝试从类 `Calendar` 切换到 `LocalDate`。`LocalDate` 不考虑时区。这应该解决您的问题（并简化您的代码）。此外，要将 `LocalDate` 格式化为 Json，请参考此问题的答案：[Spring Data JPA - ZonedDateTime format for json serialization][1]。

<details>
<summary>英文:</summary>

If Applicable try to switch from class `Calendar` to `LocalDate`. `LocalDate` does not take time zone into consideration. This should resolve your issue (and simplify your code). Also, for formatting the `LocalDate` with Json see the answer to this question: [Spring Data JPA - ZonedDateTime format for json serialization][1]


  [1]: https://stackoverflow.com/questions/31627992/spring-data-jpa-zoneddatetime-format-for-json-serialization

</details>



# 答案2
**得分**: 1

问题您面临的确与时区有关。将dob值存储在数据库中时，它以提供的确切日期和时间存储。但是，当您检索它时，会进行时区转换，导致日期看起来不同。
尝试使用 `TimeZone.setDefault(TimeZone.getTimeZone("UTC"));`
并设置 spring.datasource.url 为：jdbc:mysql://127.0.0.1:3306/database?serverTimezone=UTC

<details>
<summary>英文:</summary>

The issue you&#39;re facing is indeed related to time zones. When you store the dob value in the database, it&#39;s stored as the exact date and time provided. However, when you retrieve it, the time zone conversion takes place, causing the date to appear different.
Try use `TimeZone.setDefault(TimeZone.getTimeZone(&quot;UTC&quot;));`
and set spring.datasource.url: jdbc:mysql://127.0.0.1:3306/database?**serverTimezone=UTC**

</details>