eventsourcing/es4j

Problem: impossible to define indices in Scala

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#174 opened on Oct 29, 2016

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help wanted

Description

According to a report by @bsrk, and subsequent verification, Scala does not support static fields in classes. It does have companion objects, however, since Scala does not consider it a class and it is therefore impossible to specify it in the @Indices(Array(MyEventIndices)) annotation.

Proposed solution: implement a ScalaObjectIndexLoader that will use Scala's own reflection, but other ideas are welcome.

Temporary workaround (for those who need one): write your index definitions in separate Java classes and refer to them in @Indices(...) annotations.

Contributor guide

Tech stack
javascala
Domain
backend
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Scala knowledgeJava interopreflection
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
45
Research direction
The issue is about adding support for defining indices in Scala within the es4j framework. The problem is that Scala's companion objects are not recognized as classes for the @Indices annotation. The proposed solution is to create a ScalaObjectIndexLoader that uses Scala's own reflection to load indices from companion objects. The contributor should examine how the existing Java index loading works (likely in Java classes) and then implement a Scala specific loader. Since there are no comments or PRs, the contributor can start fresh. Relevant files might include existing index loaders or the annotation definition. The implementation should handle Scala's reflection to get the static fields from the companion object.