protostuff-runtime can't convert interface to .protp

[tangmin823]

If this tool convert java interface to proto, it will throw exception

Exception in thread "main" java.lang.RuntimeException: The root object can neither be an abstract class nor interface: "org.cango.demo.service.CarService
	at com.dyuproject.protostuff.runtime.RuntimeSchema.createFrom(RuntimeSchema.java:180)
	at com.dyuproject.protostuff.runtime.RuntimeSchema.createFrom(RuntimeSchema.java:156)
	at com.dyuproject.protostuff.runtime.IdStrategy.newSchema(IdStrategy.java:129)
	at com.dyuproject.protostuff.runtime.DefaultIdStrategy$Lazy.getSchema(DefaultIdStrategy.java:630)
	at com.dyuproject.protostuff.runtime.RuntimeSchema.getSchema(RuntimeSchema.java:119)
	at com.dyuproject.protostuff.runtime.RuntimeSchema.getSchema(RuntimeSchema.java:111)
	at net.webby.protostuff.runtime.NestedObjectTest.main(NestedObjectTest.java:28)

Code quoted:

public static void main(String[] args) {
      Schema<CarService> schema = RuntimeSchema.getSchema(CarService.class);
      String content = Generators.newProtoGenerator(schema).generate();
      System.out.println(content);
}

public interface CarService {

    Page<CarModelVO> findModelListBySeriesId(CarModelCondition condition);

}

@Getter
@Setter
@AllArgsConstructor
@NoArgsConstructor
public class Page<T> {
    private Pagination page;
    private List<T> results;

    public Page(Pagination pagination) {
        this.page = pagination;
    }

}