How to send array with Spring RestTemplate?

Question

How do I send array parameter with Spring RestTemplate?

This is the server side implementation:

@RequestMapping(value = \"/train\", method = RequestM         


        

Answer 1

Try this

Change your request mapping from

@RequestMapping(value = "/train", method = RequestMethod.GET)

to

 @RequestMapping(value = "/train/{category}/{positiveDocId[]}/{negativeDocId[]}", method = RequestMethod.GET)

and your URL in restTemplate

change URl in the below given format

http://localhost:8080/admin/train/category/1,2,3,4,5/6,7,8,9

Answer 2

Here's how I've achieved it:

The REST Controller:

@ResponseBody
@RequestMapping(value = "/test", method = RequestMethod.GET)
public ResponseEntity<Response> getPublicationSkus(
       @RequestParam(value = "skus[]", required = true) List<String> skus) {
    ...
}

The request:

List<String> skus = Arrays.asList("123","456","789");

Map<String, String> params = new HashMap<>();
params.put("skus", toPlainString(skus));

Response response = restTemplate.getForObject("http://localhost:8080/test?skus[]={skus}", 
                                      Response.class, params);

Then you just need to implement a method that converts the List or the String[] to a plain string separated by commas, for example in Java 8 would be something like this:

private static String toPlainString(List<String> skus) {
    return skus.stream().collect(Collectors.joining(","));
}

Answer 3

I ended up constructing the URL by looping through the collection.

Map<String, Object> map = new HashMap<String, Object>();
map.put("category", parameters.getName());

String url = "http://localhost:8080/admin/train?category={category}";
if (positiveDocs != null && positiveDocs.size() > 0) {
    for (String id : positiveDocs) {
        url += "&positiveDocId[]=" + id;
    }
}
if (negativeDocId != null && negativeDocId.size() > 0) {
    for (String id : negativeDocId) {
        url += "&negativeDocId[]=" + id;
    }
}

TrainResponse response = restTemplate.getForObject(url, TrainResponse.class, map);

Answer 4

Spring's UriComponentsBuilder does the trick and allows also for Variable expansion. Assuming that you want to pass an array of strings as param "attr" to a resource for which you only have a URI with path variable:

UriComponents comp = UriComponentsBuilder.fromHttpUrl(
    "http:/www.example.com/widgets/{widgetId}").queryParam("attr", "width", 
        "height").build();
UriComponents expanded = comp.expand(12);
assertEquals("http:/www.example.com/widgets/12?attr=width&attr=height", 
   expanded.toString());

Otherwise, if you need to define a URI that is supposed to be expanded at runtime, and you do not know the size of the array in advance, use an http://tools.ietf.org/html/rfc6570 UriTemplate with {?key*} placeholder and expand it with the UriTemplate class from https://github.com/damnhandy/Handy-URI-Templates.

UriTemplate template = UriTemplate.fromTemplate(
    "http://example.com/widgets/{widgetId}{?attr*}");
template.set("attr", Arrays.asList(1, 2, 3));
String expanded = template.expand();
assertEquals("http://example.com/widgets/?attr=1&attr=2&attr=3", 
    expanded);

For languages other than Java see https://code.google.com/p/uri-templates/wiki/Implementations.