How to implement JsonSerializer's serialize in general case?

Question

In manual there is a sample, containing only primitive case.

What if my case is not primitive?

Suppose I have a class, which has a problems with default serializing (in my case it is endless recursion).

Th class contain multiple fields, some of them are "main" and hold the information while another ones are service.

So I need to serialize only "main" fields and derive service ones from them.

class MyType1 {
   MyType2 a; // "main" field
   MyType3 b; // service fiels
}

class MySerializer implements JsonSerializer<MyType1> {
    @Override
    public JsonElement serialize(MyType1 arg0, Type arg1, JsonSerializationContext arg2) {
        JsonObject ans = new JsonObject();
        // ans.add("a", ... // what to write here? How to wrap a into JsonElement?
        return ans;
    }
}

I know I can use transient keyword for this specific case. But the question is about writing serializers.

UPDATE

I emphasize that using transient is not an answer. My question is about custom serializers. How to write them?

It's unclear what you're asking here. If you don't want to serialize certain fields in your serializer you just ... wouldn't add them to the JsonElement you're returning. — Brian Roach, Mar 03 '14 at 19:14
How to add only `a` to `JsonElement`? How to add anything to `JsonElement`, knowing it is abstract class? — Suzan Cioc, Mar 04 '14 at 10:07

Devrim · Answer 1 · 2014-03-03T21:17:27.897

1

class MyTypeToSerialize {
   MyType2 a; // "main" field
}

class MyType1 extends MyTypeToSerialize {
   MyType3 b; // service fiels
}

If you just want the field MyType2 a to be serialized/deserialized then use MyTypeToSerialize (you don't need a custom serializer or deserialiser)

Edit: @Brian Roach's suggestion is better and easier solution:

class MyType1 {
   MyType2 a; // "main" field
   transient MyType3 b; // service fiels
}

Edit2:

So I need to serialize only "main" fields and derive service ones from them.

So use on of the suggestions above.

I know I can use transient keyword for this specific case. But the question is about writing serializers.

Why do you think you need serializers?

edited Mar 03 '14 at 21:17

answered Mar 03 '14 at 20:45

Devrim

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Simply marking `b` as `transient` would do the same thing. – Brian Roach Mar 03 '14 at 20:50
@BrianRoach I know about `transient`, but my question is about custom serializers. – Suzan Cioc Mar 04 '14 at 10:08
@aegean I don't want to change class hierarchy, I want to write custom serializer, leaving class structure intact. – Suzan Cioc Mar 04 '14 at 10:10

score 0 · Answer 2 · answered Mar 04 '14 at 10:24

0

One should use context.serialize to delegate, like this:

class MySerializer implements JsonSerializer<MyType1> {
    @Override
    public JsonElement serialize(MyType1 arg0, Type arg1, JsonSerializationContext arg2) {
        JsonObject ans = new JsonObject();
        JsonElement a = arg2.serialize(a);
        ans.add("a", a);
        return ans;
    }
}

I found an answer here: http://www.javacreed.com/gson-serialiser-example/ , section "Nested Objects"

answered Mar 04 '14 at 10:24

Suzan Cioc

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I couldn't understand why you don't want to use transient property? Why you need a custom serializer? – Devrim Mar 04 '14 at 10:55

How to implement JsonSerializer's serialize in general case?

2 Answers2