AI Agents with Java — example source code

Companion examples for AI Agents with Java by Alex Soto Bueno, Markus Eisele, and Mario Fusco, published by O’Reilly Media.

Read the book on O’Reilly · Book organization

Explore agent coordination, memory, retrieval, tool use, communication protocols, security, and observability through Java and Quarkus examples.

Find an example

Each project has its own pom.xml and dependencies. There is no root Maven build; run commands from the example’s directory.

Directory	Topics and projects
ch03/chatmemory	Chat memory, persistent memory, and input/output guardrails
ch05	Agentic workflows, supervisors, goal-oriented action planning (GOAP), and peer-to-peer coordination
ch07	Retrieval-augmented generation (RAG), HTML transformation, query compression, and Presidio document transformation
ch08/current-time-tool	Tool calling, low-level tool execution, and dynamic tools
ch10	Model Context Protocol (MCP) clients and servers, incident management, resources, and advanced server features
ch11	Agent2Agent (A2A) clients and agents, human interaction, security, and replication
ch13	Action policies, approval validation, context selection, audit events, and isolated Java execution
ch14/observability	Agent tracing and metrics with OpenTelemetry, Grafana, and LangSmith
ch77	Embeddings, chunking, hybrid search, multimodal RAG, movie recommendations, and shopping question answering

This index follows the source directories in this checkout. Use the book alongside each example for its explanation and context.

Prerequisites

• JDK: Check the selected project’s pom.xml. Projects target Java 17, 21, or 25; several require JDK 25 to compile.
• Maven: Use ./mvnw where a wrapper is included, or an installed Maven where it is absent. On Windows, use mvnw.cmd for projects with a wrapper.
• Model access: Requirements vary by example, as described below.
• Additional services: Some projects need containers, databases, or other services. MCP clients that launch npx also need Node.js and npm.

Check which Java installation your build uses:

java -version
mvn --version

Get started without model credentials

Clone the source repository and run the Chapter 13 action-policy example with JDK 21 or later and Maven:

git clone https://github.com/ai-agents-with-java-book/ai-agents-with-java-book-src.git
cd ai-agents-with-java-book-src/ch13
mvn compile
java -cp target/classes org.acme.security.ActionPolicyExample

The example evaluates proposed actions and prints:

DRAFT_REPLY: ALLOW / DRAFT_ONLY
REQUEST_REPLACEMENT: REQUIRE_APPROVAL / REVIEW_REPLACEMENT
EXPORT_CASES: DENY / OPERATION_NOT_GRANTED
OTHER_CASE: CASE_ACCESS_DENIED

See the Chapter 13 README for the other security examples and the separate container requirements for isolated execution.

Run a tool-calling example

From the repository root, use JDK 21 or later to build and run the current-time tool:

cd ch08/current-time-tool
./mvnw package
java -jar target/my-app-1.0-SNAPSHOT-jar-with-dependencies.jar

The application asks a model to answer a date-and-time question using the Java Clock tool. Its source is configured for the LangChain4j demo endpoint with the demo API key, so it needs network access and depends on that service’s availability.

Other standalone Java projects can contain several main classes. Select the class for the example you are following; do not assume every project’s packaged JAR launches every example.

Configure model access

There is no shared model configuration for the repository. Inspect the selected project’s Java model builder and, for Quarkus applications, src/main/resources/application.properties.

• Chat memory: ch03/chatmemory uses Ollama with qwen2.5:7b. Its default address is http://127.0.0.1:11434; OLLAMA_BASE_URL overrides it. Make the model available in Ollama before running an example.
• Chapter 5: Model providers read OPENAI_API_KEY; alternative provider code also references CEREBRAS_API_KEY.
• Demo-backed examples: Several RAG, tool, and MCP examples configure the LangChain4j demo endpoint directly in source.
• Observability: ch14/observability requires OPENAI_API_KEY. The LangSmith profile also uses LANGSMITH_API_KEY, with optional LANGSMITH_PROJECT and LANGSMITH_OTLP_ENDPOINT settings.

Run Quarkus applications

From a Quarkus project directory, start development mode after configuring its required services:

./mvnw quarkus:dev

For projects without a wrapper, such as ch14/observability, use:

mvn quarkus:dev

Examples using Quarkus Dev Services need a running compatible container engine. Check the project configuration for ports and service dependencies, especially when running an MCP or A2A client and server together.

Report a problem

Open an issue with the example directory, Java and Maven versions, command you ran, and relevant error output. Remove credentials from logs before sharing them.