Empty query parameter leads to collection of null

[dsvensson]

Consider the following endpoint:

	@GET
	fun listStuff(@QueryParam("id") ids: Set<UUID>): List<Stuff> {
		...
	}

When issuing curl http://localhost/liststuff?id= .. that is, id without a value. The Set<UUID> ids will be a set that contains one null item.

I've tried adding @NotEmpty Set<UUID>, and Set<@NotNull UUID> and various permutations, without getting the endpoint to reject the request.

Is this a known limitation or am I missing something?

[joschi]

@dsvensson Thanks for reporting this!

What you describe is the default behavior of Jersey 2.x.

Example (no Dropwizard-specific classes whatsoever):

import org.glassfish.jersey.server.ResourceConfig;
import org.glassfish.jersey.test.JerseyTest;
import org.junit.Test;

import javax.ws.rs.*;
import javax.ws.rs.core.*;
import java.util.List;
import java.util.UUID;

import static org.junit.Assert.assertEquals;

public class Issue3435 extends JerseyTest {
    @Override
    protected Application configure() {
        return new ResourceConfig(TestResource.class);
    }

    @Test
    public void emptyStringQueryParamReturnsListWithOneNullElement() {
        Response response = target("test")
            .queryParam("list", "")
            .request()
            .get();
        assertEquals(200, response.getStatus());
        assertEquals("1: [null]", response.readEntity(String.class));
    }

    @Test
    public void missingQueryParamReturnsEmptyList() {
        Response response = target("test")
            .request()
            .get();
        assertEquals(200, response.getStatus());
        assertEquals("0: []", response.readEntity(String.class));
    }

    @Test
    public void filledQueryParamReturnsListWithOneElement() {
        Response response = target("test")
            .queryParam("list", "ec0cf621-d744-4a1c-b1d8-4b8a44b3dad7")
            .request()
            .get();
        assertEquals(200, response.getStatus());
        assertEquals("1: [ec0cf621-d744-4a1c-b1d8-4b8a44b3dad7]", response.readEntity(String.class));
    }

    @Path("test")
    public static class TestResource {
        @GET
        public String test(@QueryParam("list") List<UUID> list) {
            return list.size() + ": " + list.toString();
        }
    }
}

A similar issue has been filed for Jersey in eclipse-ee4j/jersey#563, but it looks like the behavior has changed again.

Would you mind filing an issue at https://github.com/eclipse-ee4j/jersey/issues to sort this out?