Gson to json conversion with DateFormat

Question

I've been reading some questions like Java Gson to Json Conversion or Gson to json conversion with two DateFormat but I'm stilling without find a solution. The problems is that when I create a new user, I'm using SimpleDateFormat to set their register date:

long date = Calendar.getInstance(new Locale("es","ES")).getTimeInMillis();

DateFormat formatter = new SimpleDateFormat(FORMATO_FECHA, new Locale("es", ""));
return formatter.format(date);

This date is storing in mysql as "2022-10-12 13:54".

Then, when I recovery the user's data (for example when login), I use Gson

JSONObject jsUser = aDatas.getJSONObject("result");
        
GsonBuilder gsonBuilder = new GsonBuilder();     
gsonBuilder.registerTypeAdapter(java.util.Date.class, new DateDeserializer());
Gson gson = gsonBuilder.create();
       
User user = gson.fromJson(String.valueOf(jsUser),User.class);

My user java model has a field to store the registration date as a Date:

class User{
    ...
    private Date mRegistrationDate;
    ...

}

The DateDeserializer class:

public class DateDeserializer implements JsonDeserializer<java.util.Date> {

private static final String[] DATE_FORMATS = new String[] {
        "MMM dd, yyyy HH:mm:ss",
        "MMM dd, yyyy",
        "yyyy-MM-dd HH:mm:ss"
};

@Override
public Date deserialize(JsonElement jsonElement, Type typeOF,
                        JsonDeserializationContext context) throws JsonParseException {
    for (String format : DATE_FORMATS) {
        try {

            return new SimpleDateFormat(format, Locale.US).parse(jsonElement.getAsString());
        } catch (ParseException e) {
        }
    }
    throw new JsonParseException("Unparseable date: \"" + jsonElement.getAsString()
            + "\". Supported formats: " + Arrays.toString(DATE_FORMATS));
}

}

If I want to show the user registration date, it's shown as "Wed Oct 12 15:45:13 GMT+00:00 2022". That break's showing the following:

java.text.ParseException: Unparseable date: "Wed Oct 12 15:45:13 GMT+00:00 2022" (at offset 0)

I tried using old gson version but it does not work.

I'm using Volley to post and retrieve json data from an api.

I hope find a solution soon. Thanks in advance.

score 0 · Answer 1 · answered Oct 12 '22 at 16:38

Non of the formats you specified matches the format of Wed Oct 12 15:45:13 GMT+00:00 2022. The correct format would be:

EEE MMM dd HH:mm:ss z yyyy

Refer to the documentation of SimpleDateFormat when building the possible formats.

Additional note: SimpleDateFormat, Date and so on are part of the legacy java date API, which is notorious for being troublesome and error prone. If possible move away from it and use java.time, the modern java date-time API, it's available since java 8. For your use case DateTimeFormatter for the formats and OffsetDateTime being the actual date time representation you need.

Well, finally I could solve the problem. When gson returns date as "Wen 2022-10-12 ...", I formatted it again as the way that I need "yyy-MM-dd HH:mm:ss" and It worked. I know that is not the best solution but for the moment I can't use java.time 'cause android app crashes if is executing in an old version. Of course, I'm taking note about investigate and change the way of I'm working with dates. Thanks for your answer! — AlphaDeveloper, Oct 13 '22 at 10:23

Gson to json conversion with DateFormat

1 Answers1