On Fri, Dec 21, 2018 at 12:06 AM matt Smith <[email protected]> wrote:
>
> so I have made this wrapper and annotated getter with @JsonSerialize.
> however, I do not see it being applied. what is wrong here?
That looks like it should work. If not, a unit test & issue would make sense.
-+ Tatu +-
>
> public class Wrapper {
>
>
> private Map<RecordDomain, ItemRow> foo;
>
>
> public Wrapper(Map<RecordDomain, ItemRow> fooz) {
> foo = new HashMap<>(fooz);
> }
>
>
> @JsonSerialize( contentUsing = ItemRowSerializer.class)
> public Map<RecordDomain, ItemRow> getFoo() {
> return foo;
> }
>
>
> public void setFoo(Map<RecordDomain, ItemRow> foo) {
> this.foo = foo;
> }
> }
>
>
> On Thursday, December 20, 2018 at 1:25:59 PM UTC-8, Tatu Saloranta wrote:
>>
>> On Thu, Dec 20, 2018 at 11:22 AM matt Smith <[email protected]> wrote:
>> >
>> > I encountered a case where class level JsonSerializable annotation does
>> > not require registration with Simple Module but method level does.
>>
>> Hmmh. This seems odd, let's see.
>>
>> > Here is the example I tried
>> >
>> > @JsonSerialize(using = ItemRowSerializer.class )
>> > private ItemRow tes
>> > tItem(){
>> > return new ItemRow("abc", Arrays.asList("item1", "item2",
>> > "item3"));
>> > }
>> >
>> >
>> > I test it out like this
>> >
>> >
>> > String jsonResult = new ObjectMapper().writeValueAsString(testItem());
>> > System.out.println(jsonResult);
>> >
>> > I noticed that jsonString did not serialize using ItemRowSerializer.
>>
>> Ah. No, it won't. Jackson does not see you calling the method; Jackson
>> sees the object you pass, which was returned by the method. There is
>> no linkage there: Jackson can only introspects classes you pass to it.
>>
>> > However, when I did this, it gave the expected jsonString
>> >
>> >
>> > SimpleModule module = new SimpleModule()
>> > module.addSerializer(ItemRowSerializer.class)
>> > mapper.register(module);
>> > String jsonResult = new ObjectMapper().writeValueAsString(testItem());
>> > System.out.println(jsonResult);
>> >
>> >
>> > On the otherhand, if I had my ItemRow class annoated with
>> > @JsonSerializable, there was no need with module at all.
>>
>> I think you mean `@JsonSerialize` here (there is interface type
>> `JsonSerializable`, but no annotation).
>>
>> > i.e
>> >
>> > @JsonSerializable(using = ItemRowSerailizer
>> > public class ItemRow<T> {...}
>> >
>> >
>> > Since I am passing this serialized object over the wire, I do not prefer
>> > to write to mapper and send string representation across.
>> >
>> > how would I go about getting method level annotation working without
>> > module registration?
>>
>> Method level annotations only work when property is accessed via
>> method (or field) in question.
>>
>> So if you had something like:
>>
>> public class Rows
>> @JsonSerialize(using = .... )
>> public ItemRow<Type> getRows() { ... }
>> }
>>
>> and serialized an instance of `Rows`, serializer would be found. But
>> for root values, there is no such reference.
>>
>> On related note, I strongly recommend always using a wrapper type
>> around generic values, so that root value is never of generic type.
>> Reason for this is that Java Type Erasure will often cause problems if
>> attempting to pass an instance of generic type -- so Jackson can not
>> detect intended type (all it sees is type variable from class
>> declaration).
>>
>> So, attempts to serialize, say, Row<T>, will be seen as `Row<?>`, and
>> possibly (although not always) cause issues in finding handlers for
>> the type -- for example, if value type has annotations, they may not
>> be visible.
>>
>> -+ Tatu +-
>
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