Multiple query parameter values as comma separated list

Question

Is it possible to build a url with multiple parameter values as a comma separated list?

The following snippet prints a url:

import org.springframework.util.LinkedMultiValueMap;
import org.springframework.util.MultiValueMap;
import org.springframework.web.util.UriComponentsBuilder;

public class MyMain {
    public static void main(String[] args) {

        MultiValueMap<String, String> queryParams = new LinkedMultiValueMap<>();
        queryParams.add("order", "1");
        queryParams.add("order", "2");

        System.out.println(UriComponentsBuilder.fromHttpUrl("http://example.com")
            .queryParams(queryParams)
            .build()
            .toString());
    }
}

The url produced by this code is:

http://example.com?order=1&order=2

What I would like to get is:

http://example.com?order=1,2

Using another framework is not an option and since I'm using a framework I would like to avoid building the logic to compose the url my way.

Is there anything in spring web or spring boot that can do this?

Answer 1

I had the same problem but I couldn't find any Spring solution either. Therefore I wrote a simple helper function for that:

@Test
public void testCreateValidMatrixVariableUrl() {
    MultiValueMap<String, String> queryParams = new LinkedMultiValueMap<>();
    queryParams.add("order", "1");
    queryParams.add("order", "2");

    String invalidUrl = UriComponentsBuilder.fromHttpUrl("http://example.com")
            .path("").query("order={order}")
            .buildAndExpand(queryParams)
            .toString();

    assertThat(prepareMatrixVariableUrl(invalidUrl)).isEqualTo("http://example.com?order=1,2");
}

private String prepareMatrixVariableUrl(String url) {
    return url.replaceAll("\\[", "")
            .replaceAll("\\]", "")
            .replaceAll(" ", "");
}

Keep in mind that prepareMatrixVariableUrl(...) replaces all brackets ([ and ]) and spaces () because without applying the helper function, your URL variable would have a format like: http://example.com?order=[1, 2]

Answer 2

Try using String.join

import org.springframework.util.LinkedMultiValueMap;
import org.springframework.util.MultiValueMap;
import org.springframework.web.util.UriComponentsBuilder;
import java.util.Collection;
import static java.util.Arrays.asList;

public class MyMain {
    public static void main(String[] args) {

        Collection<String> values = asList("1","2");
        MultiValueMap<String, String> queryParams = new LinkedMultiValueMap<>();
        queryParams.add("order", String.join(",", values));

        System.out.println(UriComponentsBuilder.fromHttpUrl("http://example.com")
                .queryParams(queryParams)
                .build()
                .toString());
    }
}