How to enforce ACCEPT_SINGLE_VALUE_AS_ARRAY in jackson's deserialization process using annotation

Solution 1:

You can use @JsonFormat annotation,

public class MyClass {

    @JsonFormat(with = JsonFormat.Feature.ACCEPT_SINGLE_VALUE_AS_ARRAY)
    private List<String> value;

}

To work with this you need to have Jackson version min 2.7.0. You can also use other available JsonFormat Features

For version 2.6.x

@Autowired private ObjectMapper mapper;
//...

mapper.configure(DeserializationFeature.ACCEPT_SINGLE_VALUE_AS_ARRAY, true);

• Add this code to your Initializer Class.
• Or you can directly configure Jackson in your Bean Configuration

These would solve the issue but it will be activated for every deserialization process.

Solution 2:

I'm just answering my own question for clarity. One of the answers was to upgrade to the higher version so that I can use annotations. I cannot do it due to dependency restrictions of my project.

As a result, based on Michal Foksa answer I solved my problem by creating a custom deserializer. Its as below:

On my property:

@JsonDeserialize(using = CustomStringDeserializer.class)
private List<String> value;

And my Deserializer:

public class CustomStringDeserializer extends JsonDeserializer<List<String>>{

    @Override
    public List<String> deserialize(JsonParser p, DeserializationContext ctxt)
            throws IOException, JsonProcessingException {
        ObjectMapper mapper = new ObjectMapper();
        mapper.enable(DeserializationFeature. ACCEPT_SINGLE_VALUE_AS_ARRAY);
        return mapper.readValue(p, List.class);
    }

}