Multiple query parameter values as comma separated list - query-string

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());
}
}