feat(java-sdk): use common streaming utils, reverse sync streaming API layer

[SoulPancake]

Description

generates https://github.com/openfga/java-sdk/pull/261

What problem is being solved?

How is it being solved?

What changes are made to solve it?

References

Review Checklist

• [ ] I have clicked on "allow edits by maintainers".
• [ ] I have added documentation for new/changed functionality in this PR or in a PR to openfga.dev [Provide a link to any relevant PRs in the references section above]
• [ ] The correct base branch is being used, if not main
• [ ] I have added tests to validate that the change in functionality is working as expected

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Walkthrough

This PR adds Java streaming API support by introducing template files for streaming response handling. Three new classes are defined: StreamResult<T> (generic wrapper), BaseStreamingApi (abstract base for streaming), and StreamedListObjectsApi (concrete implementation). Configuration overrides are added to map these templates to their target Java source locations.

Changes

Cohort / File(s)	Summary
Configuration mapping config/clients/java/config.overrides.json	Adds four new mustache-to-destination mappings for streaming API templates: StreamResult.mustache, BaseStreamingApi.mustache, and StreamedListObjectsApi.mustache, all categorized as SupportingFiles.
Streaming response wrapper config/clients/java/template/libraries/native/StreamResult.mustache	Introduces generic StreamResult<T> class with fluent setters, Jackson annotations, and standard object overrides. Models line-by-line deserialized streaming responses containing either a result of type T or an error of type Status.
Base streaming handler config/clients/java/template/libraries/native/BaseStreamingApi.mustache	Defines abstract BaseStreamingApi<T> class with centralized HTTP streaming logic via processStreamingResponse(), line-level parsing in processLine(), robust error handling with optional errorConsumer, and HTTP request construction via buildHttpRequest().
Streamed API endpoint config/clients/java/template/libraries/native/StreamedListObjectsApi.mustache	Introduces StreamedListObjectsApi extending BaseStreamingApi<StreamedListObjectsResponse> with four overloaded streamedListObjects() methods supporting optional configuration overrides and error callbacks. Validates required parameters and constructs streaming HTTP POST requests.

Sequence Diagram(s)

sequenceDiagram
    participant Client
    participant StreamedListObjectsApi
    participant BaseStreamingApi
    participant HttpClient
    participant Consumer

    Client->>StreamedListObjectsApi: streamedListObjects(storeId, body, consumer)
    StreamedListObjectsApi->>StreamedListObjectsApi: validateParameters()
    StreamedListObjectsApi->>StreamedListObjectsApi: buildHttpRequest(POST, path, body)
    StreamedListObjectsApi->>BaseStreamingApi: processStreamingResponse(request, consumer, errorConsumer)
    BaseStreamingApi->>HttpClient: send(httpRequest)
    HttpClient-->>BaseStreamingApi: response stream
    loop For each line
        BaseStreamingApi->>BaseStreamingApi: processLine(line)
        BaseStreamingApi->>BaseStreamingApi: deserialize to StreamResult<T>
        alt Error in StreamResult
            BaseStreamingApi->>BaseStreamingApi: invoke errorConsumer(error)
        else Success
            BaseStreamingApi->>Consumer: accept(result)
        end
    end
    BaseStreamingApi-->>Client: CompletableFuture<Void>

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

• BaseStreamingApi: Extra attention needed for streaming logic correctness, error handling patterns (CompletionException unwrapping), and async consumer delivery semantics
• StreamedListObjectsApi: Verify multiple method overloads are correct and parameter validation is comprehensive
• Configuration mappings: Confirm template destination paths and file categorization are accurate

Possibly related PRs

• openfga/sdk-generator#656: Switches the Makefile to the streamed build target that produces the streaming client code generated by these new template definitions.

Suggested reviewers

• ewanharris
• rhamzeh

Pre-merge checks and finishing touches

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main changes: introducing common streaming utilities and a reverse sync streaming API layer for the Java SDK, which matches the new BaseStreamingApi, StreamResult, and StreamedListObjectsApi classes.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.

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