so I have made this wrapper and annotated getter with @JsonSerialize.
however, I do not see it being applied. what is wrong here?
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]
> <javascript:>> 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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