In the above case, I called `mapper.writeValueAsString(wrapper.getFoo());`
I changed to the following (moved to annotation to the field level). when
I write using `mapper.writeValueAsString(wrapper)`, I see the expected
serialization applied. However, extra node "foo" is added at root. is there
a way to not have it?
public class Wrapper {
@JsonSerialize(contentUsing = ItemRowSerializer.class)
private Map<RecordDomain, ItemRow> foo;
public Wrapper(Map<RecordDomain, ItemRow> fooz) {
foo = new HashMap<>(fooz);
}
public Map<RecordDomain, ItemRow> getFoo() {
return foo;
}
public void setFoo(Map<RecordDomain, ItemRow> foo) {
this.foo = foo;
}
}
On Friday, December 21, 2018 at 1:52:41 PM UTC-8, matt Smith wrote:
>
> even moving annotation to the field did not work.
> Note I have annotated class ItemRow class which ofcourse i can't since it
> is part of legacy code.
>
> On Friday, December 21, 2018 at 12:49:21 PM UTC-8, Tatu Saloranta wrote:
>>
>> 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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>
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