What could be the reason of auto datetime conversion in java api response-CodePudding

I created one simple model class User. I used Util date here.

class User{
  private int id;
  private String name;
  private Date createdAt;
}

On user post API call, I simply do setCreatedAt(new Date).

The problem is in the response, I am getting createdAt as -5.30 of the actual time. No additional time conversion method is called.

For Example, I hit the POST API user created at 28-10-2021 11:30:00 which I can see in the logs. But when it returns the response to the postman it shows 28-10-2021 06:00:00 time. There is no time conversion method in the code. I checked the return object in the return statement in debug mode even there is showing 28-10-2021 11:30:00.

I wanted to know where is this conversion happening. And how to stop this.
If it's the problem with datetime library, then which one should I use.

Extra information:
 * My system timezone is in UTC. 
 * I am using ubuntu.
 * Creating restFull APIs(JaxRs)

EDIT 1:
client and server are on the same machine(UTC timezone). For client, I am using Postman.
URL: [POST] /user
Request Body:

{
  "name": "XYZ"
}

Actual Response:

{
  "id": 1,
  "name": "XYZ",
  "createdAt: "28-10-2021 06:00:00"
}

Expected Response:

{
  "id": 1,
  "name": "XYZ",
  "createdAt: "28-10-2021 11:30:00"
}

CodePudding user response：

On user post API call, I simply do setCreatedAt(new Date).

It appears that you have not set the timezone while creating an instance of java.util.Date

By default it will set as UTC irrespective of your system timezone. You can use the https://docs.oracle.com/javase/7/docs/api/java/text/SimpleDateFormat.html instead.

final TIMEZONE = ""; // need to set the timezone here
SimpleDateFormat formatter = new SimpleDateFormat("dd-M-yyyy hh:mm:ss", Locale.ENGLISH);
formatter.setTimeZone(TimeZone.getTimeZone(TIMEZONE));

String dateInString = "28-10-2021 11:30:00"; 
Date date = formatter.parse(dateInString);

CodePudding user response：

There might be JsonFormat annotations that have timeZone issues. Please check the link for more details on the issue.jackson-data-bind issue Overriding the timezone in ObjectMapper didn't work either. You can refer the solved example by implementing a custom Date Deserializer as below:

@Component
public class CustomDateDeserializer extends StdDeserializer<Date> {

    private static final long serialVersionUID = 1L;
    private SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss"); // specify your specific timezone

     public CustomDateDeserializer() {
         this(null);
     }  

     public CustomDateDeserializer(Class<?> vc) {
         super(vc);
     }

     @Override
     public Date deserialize(JsonParser jsonparser, DeserializationContext context)
                         throws IOException, JsonProcessingException {
         String date = jsonparser.getText();
         try {
             return formatter.parse(date);
         } catch (ParseException e) {
             throw new RuntimeException(e);
         }
     }
}

Also, add the deserializer on the setter method in your bean properties.

@JsonDeserialize(using = CustomDateDeserializer.class)
public void setReturnDateTime(Date returnDateTime) {
this.returnDateTime = returnDateTime;
}