Cannot serialize nested collections about dsl-json HOT 4 CLOSED

class CollectionWriter implements JsonWriter.WriteObject<Collection> {
  private final DslJson dslJson;

  public CollectionWriter(DslJson dslJson) {
    this.dslJson = dslJson;
  }

  @Override
  public void write(JsonWriter writer, Collection value) {
    writer.writeByte((byte)'[');
    boolean isFirst = true;
    for(Object it : value) {
      if (isFirst) isFirst = false;
      else writer.writeByte((byte)',');
      if (it == null) writer.writeNull();
      else dslJson.serialize(writer, it.getClass(), it);
    }
    writer.writeByte((byte)']');
  }
}

@Test
public void testSerialization() throws IOException {
  DslJson dsl = new DslJson<Object>();
  dsl.registerWriter(Collection.class, new CollectionWriter(dsl));
  JsonWriter jw = dsl.newWriter();
  dsl.serializeMap(
      Collections.singletonMap("x",
          Collections.singletonList(Collections.singletonList("Hello"))
      ),
      jw
  );
  Assert.assertEquals("{\"x\":[[\"Hello\"]]}", jw.toString());
}