Originally published at claudeguide.io/claude-api-java-guide

Claude API Java & Spring Boot Guide: Integration Tutorial (2026)

The Claude API works with Java and Spring Boot through Anthropic's official Java SDK or direct HTTP calls — add the anthropic-java dependency, inject an Anthropic client bean, and call client.messages().create() to start. Response latency averages 800ms–1.5s for typical 500-token prompts; streaming cuts perceived latency to under 200ms for the first token. This guide covers Maven/Gradle setup, synchronous and async patterns, Spring DI wiring, streaming responses, error handling, and production best practices.

Maven and Gradle Setup

Anthropic provides an official Java SDK published to Maven Central.

Maven (pom.xml):

<dependency

---

## Async and CompletableFuture

For non-blocking Spring MVC or WebFlux controllers, wrap calls in `CompletableFuture`:

java
@async
public CompletableFuture<String

Frequently Asked Questions

Is there an official Anthropic Java SDK?

Yes. Anthropic publishes anthropic-java to Maven Central. Add the dependency to your pom.xml or build.gradle and use the Anthropic client class. As of April 2026 the latest stable version is 1.3.0.

How do I set the API key in a Spring Boot app?

Use an environment variable ANTHROPIC_API_KEY and read it via @Value("${anthropic.api-key:#{environment.ANTHROPIC_API_KEY}}") in your @Configuration class. Never hardcode keys in source code or application.properties committed to version control.

Does the Java SDK support streaming?

Yes. Call client.messages().stream(params) which returns a reactive stream. You can subscribe to ContentBlockDeltaEvent events to get token-by-token text chunks, suitable for SSE endpoints in Spring MVC or reactive handlers in WebFlux.

How do I use Claude in a Spring WebFlux reactive app?

Wrap the synchronous SDK calls in Mono.fromCallable(() -> ask(prompt)).subscribeOn(Schedulers.boundedElastic()). This offloads the blocking HTTP call to a thread pool without blocking the event loop.

What is the rate limit for the Claude API?

Default tier: 50 requests/minute, 40,000 tokens/minute for claude-sonnet-4-5. Limits scale with usage tier. Implement exponential backoff on AnthropicRateLimitException (HTTP 429). Enterprise tiers offer higher limits — contact Anthropic sales.

How does prompt caching work in Java?

Add a CacheControlEphemeral block to your system prompt parameter. The system prompt must exceed 1,024 tokens to be eligible. Cached tokens cost 10% of normal input token price, delivering up to 90% savings on repeated large prompts.

Can I use Claude for structured data extraction in Java?

Yes. Prompt Claude to return a JSON object matching your schema, then parse with Jackson (ObjectMapper). For strict schema enforcement, you can include the JSON Schema in the prompt or use Claude's tool use feature to define the expected output structure.