feat(rag): add HayStack RAG Integration

[Akika404]

AgentScope-Java Version

1.0.4-SNAPSHOT

Description

• Related to [Feature]: HayStack RAG Integration #134
• add HayStack RAG Integration

Checklist

Please check the following items before code is ready to be reviewed.

• Code has been formatted with mvn spotless:apply
• All tests are passing (mvn test)
• Javadoc comments are complete and follow project conventions
• Related documentation has been updated (e.g. links, examples, etc.)
• Code is ready for review

[cla-assistant]

All committers have signed the CLA.

[cla-assistant]

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[Akika404]

[WIP] SentenceWindowRetriever is not supported yet; Related to the contextWindows and contextDocuments properties in HayStackResponse.

SentenceWindowRetriever is now supported.

[codecov]

Codecov Report

❌ Patch coverage is 68.91566% with 129 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
.../core/rag/integration/haystack/HayStackClient.java	53.60%	44 Missing and 14 partials ⚠️
...ation/haystack/exception/HayStackApiException.java	16.66%	20 Missing ⚠️
...ntegration/haystack/HayStackDocumentConverter.java	73.58%	10 Missing and 4 partials ⚠️
...ore/rag/integration/haystack/model/ByteStream.java	0.00%	11 Missing ⚠️
.../core/rag/integration/haystack/HayStackConfig.java	92.30%	4 Missing and 3 partials ⚠️
...re/rag/integration/haystack/HayStackKnowledge.java	86.27%	4 Missing and 3 partials ⚠️
...g/integration/haystack/model/HayStackDocument.java	69.56%	7 Missing ⚠️
...g/integration/haystack/model/HayStackResponse.java	88.23%	2 Missing ⚠️
...ag/integration/haystack/model/SparseEmbedding.java	84.61%	2 Missing ⚠️
...pe/core/rag/integration/haystack/FilterPolicy.java	85.71%	1 Missing ⚠️

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[Akika404]

@AlbumenJ hi, I've submitted a PR to complete this feature.
I'd appreciate a review when you have time.
Please let me know if there's anything I can improve. Thanks!

[Copilot]

Pull request overview

This PR adds a comprehensive HayStack RAG integration to AgentScope-Java, enabling support for HayStack-based knowledge base retrieval alongside existing RAG providers (Dify, RAGFlow, Bailian, etc.).

Key Changes:

• New HayStack RAG extension module with client, configuration, and knowledge base implementation
• Support for both standard retrieval and SentenceWindowRetriever response formats
• Comprehensive test coverage with unit tests and mock server testing
• Documentation updates in both English and Chinese

Reviewed changes

Copilot reviewed 23 out of 23 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
docs/en/quickstart/installation.md	Added HayStack RAG to the dependency table for English documentation
docs/zh/quickstart/installation.md	Added HayStack RAG to the dependency table for Chinese documentation
agentscope-extensions/pom.xml	Added haystack module to extensions parent POM
agentscope-extensions/agentscope-extensions-rag-haystack/pom.xml	New module POM with OkHttp, Jackson, and Reactor dependencies
HayStackConfig.java	Configuration class with retrieval parameters, filters, and HTTP settings
HayStackClient.java	HTTP client implementation with retry logic and reactive API
HayStackKnowledge.java	Main integration implementing Knowledge interface for RAG operations
HayStackDocumentConverter.java	Utility for converting HayStack documents to AgentScope format
HayStackApiException.java	Custom exception for HayStack API errors
Model classes (HayStackDocument, HayStackResponse, etc.)	Data models for API communication
FilterPolicy.java	Enum for filter merge/replace policies
Test files	Comprehensive unit tests for all components with MockWebServer
HayStackRAGExample.java	Example demonstrating integration with ReActAgent
agentscope-distribution POMs	Added haystack module to BOM and all-in-one distribution

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