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langchain4j

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LangChain4j is an idiomatic, open-source Java library for building LLM-powered applications on the JVM. It offers a unified API over popular LLM providers and vector stores, and makes implementing too

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Type
Open Source
Visit Website GitHub (11.8k stars)

About langchain4j

LangChain4j is an open-source Java library designed to simplify building LLM-powered applications on the JVM. It provides a unified API that works with major commercial and open-source LLMs and vector stores, enabling developers to create chatbots, assistants, agents, and RAG applications. The library integrates seamlessly with enterprise Java frameworks such as Quarkus, Spring Boot, and Helidon, and supports two-way interaction between Java code and LLMs. Its extensive toolbox includes prompt templating, chat memory management, output parsing, and higher-level patterns like agents, tools, and RAG.

Key Features

Unified API over major commercial and open-source LLMs and vector stores
Seamless integration with Quarkus, Spring Boot, and Helidon
Two-way integration between Java code and LLMs
Built-in support for agents, tools, and RAG patterns
Prompt templating, chat memory management, and output parsing
Wide toolbox covering low-level and high-level LLM operations

Pros & Cons

Pros
  • Native Java support with idiomatic API for JVM developers
  • Works with all major LLM providers and vector stores via unified interface
  • Seamless integration with popular enterprise frameworks (Quarkus, Spring Boot)
  • Comprehensive built-in toolbox for common LLM patterns
  • Open-source and free to use
Cons
  • Limited to the Java/JVM ecosystem – not directly usable from other programming languages
  • May require understanding of LLM concepts and patterns to leverage advanced features

Best For

Building chatbots and virtual assistantsCreating autonomous AI agents that call Java methodsImplementing retrieval-augmented generation (RAG) applicationsDeveloping LLM-powered features in enterprise Java applications

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FAQ

What is LangChain4j?
LangChain4j is an open-source Java library that provides a unified API to interact with LLMs and vector stores, making it easier to build LLM-powered applications on the JVM.
Which Java frameworks does it integrate with?
It integrates seamlessly with Quarkus, Spring Boot, and Helidon.
What LLM patterns does it support?
It supports agents, tools, RAG, prompt templating, chat memory management, and output parsing.
Is LangChain4j free?
Yes, LangChain4j is open-source and free to use.