Adding ETags to API responses
An ETag is an HTTP response header that contains a computed hash or equivalent value of the response entity, and a minor change in the entity must change its value. HTTP request objects can then contain the If-None-Match and If-Match headers to receive the conditional responses.
Let’s call an API to retrieve the response with an ETag, as shown next:
$ curl -v --location --request GET 'http://localhost:8080/ api/v1/products/6d62d909-f957-430e-8689-b5129c0bb75e' –-header 'Content-Type: application/json' --header 'Accept: application/json'* … text trimmed
> GET /api/v1/products/6d62d909-f957-430e-8689-b5129c0bb75e HTTP/1.1
> Host: localhost:8080
> User-Agent: curl/7.55.1
> Content-Type: application/json
> Accept: application/json
>
< HTTP/1.1 200
< ETag: "098e97de3b61db55286f5f2812785116f"
< Content-Type: application/json
< Content-Length: 339
<
{
...