REST - Download list of users

Question

Context:

I want to write an endpoint that will return a Collection of users based on their usernames. How should those username be passed to the REST endpoint - note that I can (potentially) have a lot of usernames (say > 5000)?

Solution #1:

Use a GET endpoint, concatenate the usernames on client side and pass them as a single request parameter. Split the request parameter on server side to get the list of usernames.

@RestController
public class UserController { 

    @GetMapping
    // able to deserialize `filename1,filename2` to List out of the box
    public Collection<User> getUser(@RequestParam List<String> usernames) {
        return userService.getUsersByUsername(usernames);
    }

}

Solution #2:

Use a POST endpoint and pass the list of usernames as request body. Although cleaner form a coding perspective, I end up using a POST to fetch data.

@RestController
public class UserController { 

    @PostMapping
    public Collection<User> getUser(@RequestBody List<String> usernames) {
        return userService.getUsersByUsername(usernames);
    }

}

Questions:

Which of the two solutions would be the better approach?
Do you have a better approach to pass the list of usernames into the endpoint?

Edits:

I've updated the signature of the first solution based on suggestions from answers. Spring is able to deserialize filename1,filename2 to List out of the box for @RequestParam.

Given the amount of data as parameters, you'd better go with the `POST` solution. It will also be easier to test things with tools like postman. — Arnaud, Oct 05 '18 at 07:34

score 1 · Answer 1 · answered Oct 05 '18 at 07:38

POST looks like a cleaner approach in this case because -

Sending a huge string in a URL is not a good idea and there is scope for error
You need to write additional code (logic) to create the string on frontend and split it on backend.
Sending a huge string in a URL is not scalable as there are limits on the length of URL.

score 0 · Answer 2 · answered Oct 05 '18 at 07:34

0

Get approach might result into an issue since URL length is limited and then you have to limit your query parameters.

Though its not a post request but in your case i think post is the only way out.

answered Oct 05 '18 at 07:34

saurav

5,388
10
56
101

Adina Rolea · Answer 3 · 2018-10-05T12:57:46.767

GET is not limited, yet the browser is. Your server client does not seem to be the browser, so I would say GET is the way to go.

P.S GET can receive a body (not so great, but POST is not also the best match).

You don need to concatenated the string and add extra computation on server server, GET can receive a list of separate strings.

UPDATE with example:

@RestController
public class MyController {

    @GetMapping(value = "/test")
    public List<String> getTestParams(@RequestParam List<String> params) {
        return params;
    }
}

The test with 3000 params

@RunWith(SpringRunner.class)
@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
public class TestMyController {

    @Autowired
    private TestRestTemplate restTemplate;

    @Test
    public void testRequestWithParamsList() {    
        List<String> params = new ArrayList<>();
        for (int i = 0; i < 3000; i++) {
            params.add(String.valueOf(i));
        }

        List<String> result = restTemplate.getForObject(buildUrl(params),
                List.class);

        assertEquals(params, result);
    }

    private String buildUrl(List<?> params) {
        return "/test?params=" + getUrlParameter(params);

    }

    private String getUrlParameter(List<?> params) {
        return params.stream()
                .map(Object::toString)
                .collect(Collectors.joining(","));
    }
}

If you are using tomcat you must specify also the max http header property in application.properties

server.max-http-header-size=30000

The GET request body can be tricky, see https://stackoverflow.com/questions/978061/http-get-with-request-body — , Oct 05 '18 at 08:36
Do you have a working snipped of receiving a List as `@RequestParam`? See https://pastebin.com/9aBZXqQ1 for some snippets. — , Oct 05 '18 at 08:37

score 0 · Answer 4 · answered Oct 05 '18 at 10:41

I would agree with all the answers given above. I would like to specify one more point , if you are going with post request you might have to increase the payload capacity a server can receive , the default post capacity(The maximum size in bytes) of spring boot is 2mb (based on your server). While testing your code might work fine with 1000-2000 usernames but make sure to change the property to accept more bytes in request.

REST - Download list of users

4 Answers4