Deserializing from JSON back to joda DateTime in Play 2.0 - json

Question

I can't figure out the magic words to allow posting JSON for a DateTime field in my app. When queried, DateTimes are returned as microseconds since the epoch. When I try to post in that format though ({"started":"1341006642000","task":{"id":1}}), I get "Invalid value: started".
I also tried adding #play.data.format.Formats.DateTime(pattern="yyyy-MM-dd HH:mm:ss") to the started field and posting {"started":"2012-07-02 09:24:45","task":{"id":1}} which had the same result.
The controller method is:
#BodyParser.Of(play.mvc.BodyParser.Json.class)
public static Result create(Long task_id) {
Form<Run> runForm = form(Run.class).bindFromRequest();
for (String key : runForm.data().keySet()) {
System.err.println(key + " => " + runForm.apply(key).value() + "\n");
}
if (runForm.hasErrors())
return badRequest(runForm.errorsAsJson());
Run run = runForm.get();
run.task = Task.find.byId(task_id);
run.save();
ObjectNode result = Json.newObject();
result.put("id", run.id);
return ok(result);
}
I can also see from the output that the values are being received correctly. Anyone know how to make this work?

Answer 1

After reading the "Register a custom DataBinder" section of the Handling form submission page along with the Application global settings page and comparing with this question I came up with the following solution:
I created a custom annotation with an optional format attribute:
package models;
import java.lang.annotation.*;
#Target({ ElementType.FIELD })
#Retention(RetentionPolicy.RUNTIME)
#play.data.Form.Display(name = "format.joda.datetime", attributes = { "format" })
public #interface JodaDateTime {
String format() default "";
}
and registered a custom formatter from onStart:
import java.text.ParseException;
import java.util.Locale;
import org.joda.time.DateTime;
import org.joda.time.format.DateTimeFormat;
import play.*;
import play.data.format.Formatters;
public class Global extends GlobalSettings {
#Override
public void onStart(Application app) {
Formatters.register(DateTime.class, new Formatters.AnnotationFormatter<models.JodaDateTime,DateTime>() {
#Override
public DateTime parse(models.JodaDateTime annotation, String input, Locale locale) throws ParseException {
if (input == null || input.trim().isEmpty())
return null;
if (annotation.format().isEmpty())
return new DateTime(Long.parseLong(input));
else
return DateTimeFormat.forPattern(annotation.format()).withLocale(locale).parseDateTime(input);
}
#Override
public String print(models.JodaDateTime annotation, DateTime time, Locale locale) {
if (time == null)
return null;
if (annotation.format().isEmpty())
return time.getMillis() + "";
else
return time.toString(annotation.format(), locale);
}
});
}
}
You can specify a format if you want, or it will use milliseconds since the epoch by default. I was hoping there would be a simpler way since Joda is included with the Play distribution, but this got things working.
Note: you'll need to restart your Play app as it doesn't seem to detect changes to the Global class.