Feigning lists

build.gradle

apply plugin: 'java'

repositories {
    jcenter()
}

def feign = { "com.netflix.feign:feign-$it:6.1.2" }

dependencies {
    compile feign("jackson"), feign("jaxrs")

    testCompile 'junit:junit:4.12'
    testCompile 'org.assertj:assertj-core:3.0.0'
}

CartesianPoint.java

package testo;

import com.fasterxml.jackson.annotation.JsonTypeName;

@JsonTypeName("cartesian")
public class CartesianPoint implements Point {
    public double x, y;

    public CartesianPoint(double x, double y) {
        this.x = x;
        this.y = y;
    }
}

FakeService.java

package testo;

import javax.ws.rs.Consumes;
import javax.ws.rs.POST;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;
import java.util.List;

public interface FakeService {
    @Consumes(MediaType.APPLICATION_JSON)
    @POST
    @Path("/")
    @Produces(MediaType.APPLICATION_JSON)
    void doSomething(List<Point> args);

    @Consumes(MediaType.APPLICATION_JSON)
    @POST
    @Path("/")
    @Produces(MediaType.APPLICATION_JSON)
    void doSomething(Point[] args);
}

FakeServiceTests.java

package testo;

import feign.Feign;
import feign.jackson.JacksonModule;
import feign.jaxrs.JAXRSModule;
import org.junit.Test;

import java.util.Arrays;

public class FakeServiceTests {
    private static final Point[] POINTS = new Point[] {
            new CartesianPoint(2.0, 3.0),
            new PolarPoint(2.0, 3.0)
    };

    private final FakeService service = Feign.create(
            FakeService.class, "http://localhost:8000",
            new JAXRSModule(), new JacksonModule());

    @Test
    public void testList() {
        service.doSomething(Arrays.asList(POINTS));
    }

    @Test
    public void testArray() {
        service.doSomething(POINTS);
    }
}

Point.java

package testo;

import com.fasterxml.jackson.annotation.JsonSubTypes;
import com.fasterxml.jackson.annotation.JsonTypeInfo;

@JsonTypeInfo(
        use = JsonTypeInfo.Id.NAME,
        include = JsonTypeInfo.As.WRAPPER_OBJECT)
@JsonSubTypes({
        @JsonSubTypes.Type(CartesianPoint.class),
        @JsonSubTypes.Type(PolarPoint.class)
})
public interface Point {
    // marker-only
}

PolarPoint.java

package testo;

import com.fasterxml.jackson.annotation.JsonTypeName;

@JsonTypeName("polar")
public class PolarPoint implements Point {
    public double r, θ;

    public PolarPoint(double r, double θ) {
        this.r = r;
        this.θ = θ;
    }
}