.js

package com.serverless;
...
import com.serverless.dal.Product;

public class GetProductHandler implements RequestHandler<Map<String, Object>, ApiGatewayResponse> {

	private final Logger logger = Logger.getLogger(this.getClass());

	@Override
	public ApiGatewayResponse handleRequest(Map<String, Object> input, Context context) {

    try {
        // get the 'pathParameters' from input
        Map<String,String> pathParameters =  (Map<String,String>)input.get("pathParameters");
        String productId = pathParameters.get("id");

        // get the Product by id
        Product product = new Product().get(productId);

        // send the response back
        if (product != null) {
          return ApiGatewayResponse.builder()
      				.setStatusCode(200)
      				.setObjectBody(product)
      				.setHeaders(Collections.singletonMap("X-Powered-By", "AWS Lambda & Serverless"))
      				.build();
        } else {
          return ApiGatewayResponse.builder()
                .setStatusCode(404)
                .setObjectBody("Product with id: '" + productId + "' not found.")
                .setHeaders(Collections.singletonMap("X-Powered-By", "AWS Lambda & Serverless"))
                .build();
        }
    } catch (Exception ex) {
        logger.error("Error in retrieving product: " + ex);

        // send the error response back
        ...
    }
  }
}