在Lagom中访问URL查询参数

import com.lightbend.lagom.javadsl.api.*;
import com.lightbend.lagom.javadsl.api.transport.Method;

public interface MyService extends Service {
    ServiceCall<NotUsed, String> getWithQueryParam(String param);

    @Override
    default Descriptor descriptor() {
        return named("myservice").withCalls(
                restCall(Method.GET, "/api/resource?param", this::getWithQueryParam)
        ).withAutoAcl(true);
    }
}

import com.lightbend.lagom.javadsl.api.ServiceCall;
import com.lightbend.lagom.javadsl.api.transport.BadRequest;
import com.lightbend.lagom.javadsl.api.transport.ResponseHeader;
import com.lightbend.lagom.javadsl.api.transport.SimpleResponseHeader;
import com.lightbend.lagom.javadsl.server.HeaderServiceCall;
import org.pcollections.HashTreePMap;
import org.pcollections.PMap;

public class MyServiceImpl implements MyService {
    @Override
    public ServiceCall<NotUsed, String> getWithQueryParam(String param) {
        return HeaderServiceCall.compose(request -> {
            String queryParam = request.getQueryString("param").orElse(null);
            if (queryParam == null) {
                throw new BadRequest("Missing query parameter: param");
            }
            return CompletableFuture.completedFuture("Query parameter value: " + queryParam);
        });
    }
}