How to use query parameter represented as JSON with Spring RestTemplate?

Question

I need to make a request to an HTTP endpoint having a query parameter represented as JSON using Spring RestTemplate.

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Answer 1

What is wrong with using writeValueAsString ? Can You explain?

The only solution that comes to my mind looks like (I don't think if there is a way for Jackson to know that this object should be serialized in that moment):

@Autowired
ObjectMapper objectMapper;

@Override
public void run(String... strings) throws Exception {

    String urlBase = "http://localhost:8080/path";

    RestTemplate restTemplate = new RestTemplate();

    String url;
    MultiValueMap params = new LinkedMultiValueMap();
    params.set("object", objectMapper.writeValueAsString(new MyObject()));

    UriComponentsBuilder builder = UriComponentsBuilder.fromHttpUrl(urlBase).queryParams(params);
    url = builder.build().toUri().toString();

    LOGGER.info("Composed before decode: " + url);

    //restTemplate.getForObject(url, Void.class);

    url = URLDecoder.decode(url, "UTF-8");

    LOGGER.info("Composed after decode: " + url);
}

Output:

2016-04-05 16:06:46.811  INFO 6728 --- [main] com.patrykwoj.StackOverfloApplication    : Composed before decode: http://localhost:8080/path?object=%7B%22key%22:43%7D
2016-04-05 16:06:46.941  INFO 6728 --- [main] com.patrykwoj.StackOverfloApplication    : Composed after decode: http://localhost:8080/path?object={"key":43}

Edit:

I forgot to mention, that sending JSON object as request parameter is generally not a good idea. For example, You will probably face problem with curly brackets inside JSON.