Jackson does not honor contentUsing in @JsonSerialize under some circumstances

[fschopp]

Jackson version: 2.3.0

While trying to work around Issue #357, I found another bug.

Jackson does not honor contentUsing in @JsonSerialize under some circumstances.

static class A {
    public String unexpected = "Bye.";
}

static class B {
    @JsonSerialize(as = Iterable.class, contentUsing = ASerializer.class)
    public List<A> list = Arrays.asList(new A());
}

static class ASerializer extends JsonSerializer<A> {
    @Override
    public void serialize(A a, JsonGenerator jsonGenerator, SerializerProvider provider) throws IOException {
        jsonGenerator.writeStartArray();
        jsonGenerator.writeString("Hello world.");
        jsonGenerator.writeEndArray();
    }
}

@Test
void testBSerialization() throws Exception {
    System.out.println(new ObjectMapper().writeValueAsString(new B()));
}

This gives the following output:

{"list":[{"unexpected":"Bye."}]}

However, replacing as = Iterable.class by as = List.class gives output:

{"list":[["Hello world."]]}

[fschopp]

Looks like the IterableSerializer is somewhat out of date compared to the CollectionSerializer?

[cowtowncoder]

Ok I'll have a look. It is possible that IterableSerializer could be missing something other serializers have.

[cowtowncoder]

One quick question: is this with Java 8? I recall some oddities with java.util.Iterator on Java 8, but not enough time to dig in (I am not using 8 for anything other than building new Java 8 date/time module).

[cowtowncoder]

No, I can reproduce this with 1.7 as well. Different issue.

[cowtowncoder]

Looks like the problem is that annotation for serializer to use, for content type, gets dropped if there is as annotation property. Commenting out that property removes the problem. So need to see where type is being overridden as that is where associate handler is probably dropped.

[cowtowncoder]

Ah. It wasn't anything fancy -- as you correctly suggested, IterableSerializer was to blame; it was ignoring element serializer that was correctly passed & set, and tried to fetch serializer dynamically.
So at least one out of 3 is resolved.