AWS Lambda json deserialization with jackson annotations

Question

I'm calling an aws lambda with a json body. So the fields of the json are with different name from the ones in the POJO. So what I did is to add @JsonProperty on the fields to tell jackson what are the names in json. But for some reason it seems that it doesn't recognize them and all the fields are null. If I pass a json with the same field names as the POJO it's working. Here's my class:

public class Event implements Identifiable {

    @JsonProperty("distinct_id")
    private String distinctId;

    @JsonProperty("user_id")
    private Integer userId;

    @JsonDeserialize(using = LocalDateTimeDeserializer.class)
    @JsonSerialize(using = LocalDateTimeSerializer.class)
    private LocalDateTime eventDateTime;

    //Here are the getters and setters
}

If I pass

{"distinct_id":"123", "user_id":123, "dt":"2017-01-04T08:45:04+00:00"} 

all the fields are null and with distinctId, userId, eventDateTime it's serializing ok with the exception that it also doesn't recognize my custom serializers/deserializers but this actually is the same problem.

My conclusion is that for some reason the aws jackson is not working with the annotations but it doesn't make sense.

Answer 1

So I found a way to do this. You need to implement RequestStreamHandler which gives you input and output streams which you can work with:

import com.amazonaws.services.lambda.runtime.RequestStreamHandler

public class ChartHandler implements RequestStreamHandler {
    private ObjectMapper objectMapper = new ObjectMapper();

    @Override
    public void handleRequest(InputStream inputStream, OutputStream outputStream, Context context) throws IOException {
        DeserializationClass deserializedInput = objectMapper.readValue(inputStream, DeserializationClass.class)
        objectMapper.writeValue(outputStream, deserializedInput); //write to the outputStream what you want to return
    }

}

Having the input and output streams makes you independent of the format and frameworks you use to parse it.

Answer 2

Take a look at this quote from AWS documentation:

You shouldn't rely on any other features of serialization frameworks such as annotations. If you need to customize the serialization behavior, you can use the raw byte stream to use your own serialization.

From: https://docs.aws.amazon.com/lambda/latest/dg/java-programming-model-req-resp.html