Custom serialisation for CSV with Jackson

So, imagine I have following Java classes:

public class A {
    @JsonProperty("id")
    String id;

    @JsonProperty("name")
    String name;

    @JsonSerialize(using = PropertiesSerializer.class)
    @JsonUnwrapped
    Properties properties;
}

public class Properties {
    List<Property> properties;
}

public class Property {
    String key;
    String value;
}

class PropertiesSerializer extends JsonSerializer<Properties> {
    @Override
    public void serialize(Properties properties, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) {
        if (properties != null && properties.getProperties() != null) {
            properties.getProperties().forEach(property -> {
                try {
                    jsonGenerator.writeStartObject();
                    jsonGenerator.writeStringField(property.getKey(), property.getValue());
                    jsonGenerator.writeEndObject();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            });
        }
    }
}

What I need here is to serialize the Product object to CSV. When trying to run it, I get CSV generator does not support Object values for properties (nested Objects) error. When adding @JsonUnwrappped annotation to lower level objects, I still get stuck at some point with the same error.

Shouldn't it ignore everything and call the custom serializer for the properties field? It looks like it completely ignores this method. How do I fix that?

Btw, I can't change the code structure because of the XML conversion.

Thanks,

Currently the json that your code generates looks something like this:

{
    "id": "myId",
    "name": "myName",
    {
        "foo": "bar"
    },
    {
        "foo2": "bar2"
    },
    ...
}

I think you are just missing jsonGenerator.writeArrayFieldStart("properties") before the loop and jsonGenerator.writeEndArray() after the loop.