Various patterns can be used for Java Lambda input / output types.

Map method
POJO method
InputStream / OutputStream method

In the official documentation, it is written here.

In POJO, I introduced how to handle JSON using POJO classes.

Finally, it is the Stream edition using InputStream / OutputStream.

It is a code that is modified from the previous POJO edition and Parse and Generate by itself using Jackson.

import com.amazonaws.services.lambda.runtime.Context;
import com.amazonaws.services.lambda.runtime.RequestStreamHandler;
import com.fasterxml.jackson.databind.ObjectMapper;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Arrays;
import java.util.List;

public class StreamFunction implements RequestStreamHandler {

    private static final ObjectMapper OBJECT_MAPPER = new ObjectMapper();

    @Override
    public void handleRequest(InputStream inputStream, OutputStream outputStream, Context context) throws IOException {
        Product product = OBJECT_MAPPER.readValue(inputStream, Product.class);

        String name = product.getName();
        System.out.println(name); // orange juice

        Integer price = product.getPrice();
        System.out.println(price); // 1000

        Long releaseDate = product.getReleaseDate();
        System.out.println(releaseDate); // 1601606387939

        Double rate = product.getRate();
        System.out.println(rate); // 4.5

        List<String> rawMaterial = product.getRawMaterial();
        System.out.println(rawMaterial); // [orange, fragrance]

        Product.Size size = product.getSize();
        Integer height = size.getHeight();
        System.out.println(height); // 10

        Integer width = size.getWidth();
        System.out.println(width); // 20

        Integer depth = size.getDepth();
        System.out.println(depth); // 30

        Product response = new Product();
        response.setName("coffee");
        response.setPrice(Integer.valueOf(500));
        response.setReleaseDate(System.currentTimeMillis());
        response.setRate(Double.valueOf(4.2));
        response.setRawMaterial(Arrays.asList("coffee", "sugar"));

        Product.Size responseSize = new Product.Size();
        responseSize.setHeight(Integer.valueOf(100));
        responseSize.setWidth(Integer.valueOf(200));
        responseSize.setDepth(Integer.valueOf(300));
        response.setSize(responseSize);

        OBJECT_MAPPER.writeValue(outputStream, response);
    }
}

When executed, the result is the same as the POJO edition.

{
  "name": "coffee",
  "price": 500,
  "releaseDate": 1601627790764,
  "rate": 4.2,
  "rawMaterial": [
    "coffee",
    "sugar"
  ],
  "size": {
    "height": 100,
    "width": 200,
    "depth": 300
  }
}

I don't think I'll use it much, but maybe when I'm dealing with huge JSON or when I want to use the JSON Parser / Generator library.

Which one is better after all

For product codes, it is recommended to use the POJO method for maintainability. If you just want to move it quickly and try it out, the Map method is easy.

I tried Java Lambda input / output type ~ Stream version ~

Which one is better after all