Response.Builder API does not enforce non null requirement for headers

[cberg-zalando]

In one of our projects I just updated from feign 8.x -> 9.x and noticed that the static create methods in the Response class are now deprecated and instead the builder pattern should be used.

As we don't need to specify headers, I omitted settings those and then experienced a NullPointerException when the caseInsensitveCopyOf method was called.

I'd say, either initialize its property with a Collections.emptyMap in the builder or check for headers being not null when calling the build method.

[ImranAdan]

This is where in the Response class the failure occurs

  private Response(Builder builder) {
    checkState(builder.status >= 200, "Invalid status code: %s", builder.status);
    this.status = builder.status;
    this.reason = builder.reason; //nullable
    this.headers = Collections.unmodifiableMap(caseInsensitiveCopyOf(builder.headers));
    this.body = builder.body; //nullable
    this.request = builder.request; //nullable
  }

Fix Option:

  public static Builder builder(Map<String, Collection<String>> headers){
    return new Builder(headers);
  }

[codefromthecrypt]

a response with no headers is more often a bug than an intent. I'd say initializing to Collections.emptyMap is fine eventhough it could hide a bug. either way, fair game to print the field name in the NPE message rather than resort to looking at the line number.

[kdavisk6]

Closing due to inactivity.