How to set HTTP response HEADERS in @RestController?

The HTTP response headers are very important. It is so, because the HEADERS values can inform to the HTTP client definitions about how to receive and interpret the received data. It include important fields, such as:

·       SET-COOKIE:

·       CONTENT-TYPE:

·       Content-Language:

·       RESPONSE-CODE:

·       Accept-Language:

·       Access-Control-Allow-Methods:

·       Etc;


You can see a list here: https://en.wikipedia.org/wiki/List_of_HTTP_header_fields

 

Using Spring boot and its @RestController, although there are a few annotations and attributes (ex. @CrossOrigem, produces, etc.) that assists in the definition of how HTTP HEADERS have to be produced, it is possible to generate that with more fine control using the HttpHeaders class. Objects from this class have a method named .set(key, value), which works as a map, you can set many key/value data, and each one will be part of the HTTP Header. Once this object is created and its data assigned, it is possible to return the HTTP response to the client, composing a ResponseEntity object with the HTTPHeaders. This composition can be done by ResponseEntity constructor, as you can see in the code below:

 

private ResponseEntity buildResponseEntitySuccess(Object result) {

             HttpHeaders responseHeaders = new HttpHeaders();

           responseHeaders.set("Access-Control-Allow-Origin","*");

           responseHeaders.set("Access-Control-Allow-Credentials", "true");

           responseHeaders.set("Access-Control-Allow-Methods", "POST, GET, OPTIONS, DELETE");

           responseHeaders.set("Access-Control-Max-Age", "3600");

           responseHeaders.set("Access-Control-Allow-Headers", "Content-Type, Accept, X-Requested-With, remember-me");

        return       new ResponseEntity(result, responseHeaders, HttpStatus.OK);

       }

It is important to highlight that using ResponseEntity the @RestController still responsible to part the output as the expected content-type. Hence, you can just set any Object in the first parameter of this constructor, and Spring Boot will handle it. This way, there is not sideback effect of using ResponseEntity as the return type of a @RequestMapping, or returning a List of any specific type.

 

You can download an example of this code from github:

https://github.com/rafaelqg/code/blob/main/http_headers_rest_controller.js

 

You may watch a video class here:

https://youtu.be/zjV-yKxxNuI



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