OrderController.java

package br.com.zeroth.zth_product_srv.controller;

import br.com.zeroth.zth_product_srv.domain.Order;
import br.com.zeroth.zth_product_srv.services.OrderService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.ResponseEntity;
import org.springframework.util.DigestUtils;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("/orders")
public class OrderController {

    @Autowired
    private OrderService service;

    @GetMapping("/{id}")
    public ResponseEntity<Order> getOrder(@PathVariable Long id) {
        Order order = service.getOrderWithDetails(id);

        String eTag = generateDeepETag(order);

        return ResponseEntity.ok()
                .eTag(eTag)
                .body(order);
    }

    private String generateDeepETag(Order order) {
        String productName = order.getProduct().getName();
        String paymentStatus = order.getPayment().getStatus();
        String shippingHistory = order.getShippingHistory().getLastStatus();

        return DigestUtils.md5DigestAsHex((productName + paymentStatus + shippingHistory).getBytes());
    }
}