How to properly convert dto to json in Java?

Question

How to properly convert dto to json in Java? I do it like below with using ObjectMapper:

        ObjectDto dto;
        byte[] json = new byte[0];

        dto = service.getDto(someId);

        ObjectMapper mapper = new ObjectMapper();
        json = mapper.writeValueAsBytes(dto);

and the problem is in formatting date field. In Dto i have my date in this format: 2021-09-27T12:06:27.990Z but after convert this dto to json in bytes, I see that my date is split into object with many properties like below:

"date":{
         "year":2021,
         "month":"OCTOBER",
         "nano":528000000,
         "monthValue":10,
         "dayOfMonth":25,
         "hour":13,
         "minute":14,
         "second":58,
         "dayOfYear":298,
         "dayOfWeek":"MONDAY",
         "chronology":{
            "id":"ISO",
            "calendarType":"iso8601"
         }
      },

I want to, after using ObjectMapper to have all property from Dto in this same format as before convert. How to do this?

Thanks for any help!

Have you tried to annotate your DTO with the @JsonFormat Annotation? See the Documentation here: https://www.javadoc.io/doc/com.fasterxml.jackson.core/jackson-annotations/2.9.8/com/fasterxml/jackson/annotation/JsonFormat.html And for some examples here: https://www.baeldung.com/jackson-jsonformat — Marvin, Oct 25 '21 at 11:48
I cannot use any of the annotation cause I work on auto-generated dto's :/ — methodinvocation, Oct 25 '21 at 11:49
Does this answer your question? [Java 8 LocalDate Jackson format](https://stackoverflow.com/questions/28802544/java-8-localdate-jackson-format) (Specifically [this answer](https://stackoverflow.com/a/35062824).) — Ivar, Oct 25 '21 at 11:51
Good point @Ivar the SerializationFeature configuration should do the trick. — Marvin, Oct 25 '21 at 11:54
@Ivar I use it and this convert my date but without "Z" at the end of the date, so still throw me an exception — methodinvocation, Oct 25 '21 at 11:59
Can't you change whatever is auto-generating the DTO's, to use a `String` for the date field instead of a `LocalDateTime` and make sure that this string contains the correct value? Might save you some trouble. — Ivar, Oct 25 '21 at 12:13
it format me to this type: `"creationTime":"2021-10-25T13:14:58+02:00",` which is not this same as in dto — methodinvocation, Oct 25 '21 at 12:16

score 1 · Accepted Answer · answered Oct 25 '21 at 12:14

You should register a custom serializer

public class ItemSerializer extends StdSerializer<Item> {
  ....
}

ObjectMapper mapper = new ObjectMapper();

SimpleModule module = new SimpleModule();
module.addSerializer(Item.class, new ItemSerializer());
mapper.registerModule(module);

See the full explanation here : https://www.baeldung.com/jackson-custom-serialization

score 0 · Answer 2 · answered Oct 25 '21 at 13:19

0

Use DataType of your Date as String in your DTO. It will solve the problem

answered Oct 25 '21 at 13:19

Dhruv Singh

2,185
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How to properly convert dto to json in Java?

2 Answers2