Spring MVC: How to Properly Handle HTTP 304 Not Modified Response with Conditional Requests?
I'm building a feature where I can't seem to get I've been banging my head against this for hours..... I'm working on a Spring MVC application (version 5.3.12) that serves static resources, and I want to implement caching effectively to reduce server load. However, I'm facing issues with handling HTTP 304 Not Modified responses when clients make conditional requests using the If-None-Match header. My current configuration in the controller is as follows: ```java @Controller public class ResourceController { @GetMapping(value = "/api/resource", produces = MediaType.APPLICATION_JSON_VALUE) @ResponseBody public ResponseEntity<MyResource> getResource(HttpServletRequest request) { MyResource resource = fetchResource(); // Fetching resource logic String etag = "\"" + resource.getId() + "\""; String ifNoneMatch = request.getHeader("If-None-Match"); if (etag.equals(ifNoneMatch)) { return ResponseEntity.status(HttpStatus.NOT_MODIFIED).build(); } return ResponseEntity.ok() .eTag(etag) .body(resource); } } ``` With this setup, I'm seeing a 200 response with the resource data on repeat requests, even when the resource hasn't changed, which is not what I expect. I've also tried to add caching headers in the response like `Cache-Control: max-age=3600`, but it doesn't seem to help with the conditional requests. I've verified that the ETag is being generated correctly based on the resource's ID, but it looks like the browser isn't sending the If-None-Match header properly. I've tested this behavior using Postman and noticed that if I manually set the If-None-Match header to the correct value, I do receive a 304 response as expected. Is there a specific configuration or a best practice that I might be missing to ensure the browser correctly handles the caching and sends the If-None-Match header on subsequent requests? How can I properly implement this feature without manually configuring the client side? Any ideas what could be causing this? For reference, this is a production desktop app. I'd be grateful for any help. I've been using Java for about a year now. Am I missing something obvious?