Anthropic Java API Library

Note

The Anthropic Java API Library is currently in beta.

There may be minor breaking changes.

Have thoughts or feedback? File an issue or comment on this discussion.

The Anthropic Java SDK provides convenient access to the Anthropic REST API from applications written in Java.

The REST API documentation can be found on docs.anthropic.com. Javadocs are also available on javadoc.io.

Installation

Gradle

implementation("com.anthropic:anthropic-java:0.6.0")

Maven

<dependency>
    <groupId>com.anthropic</groupId>
    <artifactId>anthropic-java</artifactId>
    <version>0.6.0</version>
</dependency>

Requirements

This library requires Java 8 or later.

Usage

See the anthropic-java-example directory for complete and runnable examples.

import com.anthropic.client.AnthropicClient;
import com.anthropic.client.okhttp.AnthropicOkHttpClient;
import com.anthropic.models.Message;
import com.anthropic.models.MessageCreateParams;
import com.anthropic.models.Model;

// Configures using the `ANTHROPIC_API_KEY` and `ANTHROPIC_AUTH_TOKEN` environment variables
AnthropicClient client = AnthropicOkHttpClient.fromEnv();

MessageCreateParams params = MessageCreateParams.builder()
    .maxTokens(1024L)
    .addUserMessage("Hello, Claude")
    .model(Model.CLAUDE_3_7_SONNET_LATEST)
    .build();
Message message = client.messages().create(params);

Client configuration

Configure the client using environment variables:

import com.anthropic.client.AnthropicClient;
import com.anthropic.client.okhttp.AnthropicOkHttpClient;

// Configures using the `ANTHROPIC_API_KEY` and `ANTHROPIC_AUTH_TOKEN` environment variables
AnthropicClient client = AnthropicOkHttpClient.fromEnv();

Or manually:

import com.anthropic.client.AnthropicClient;
import com.anthropic.client.okhttp.AnthropicOkHttpClient;

AnthropicClient client = AnthropicOkHttpClient.builder()
    .apiKey("my-anthropic-api-key")
    .build();

Or using a combination of the two approaches:

import com.anthropic.client.AnthropicClient;
import com.anthropic.client.okhttp.AnthropicOkHttpClient;

AnthropicClient client = AnthropicOkHttpClient.builder()
    // Configures using the `ANTHROPIC_API_KEY` and `ANTHROPIC_AUTH_TOKEN` environment variables
    .fromEnv()
    .apiKey("my-anthropic-api-key")
    .build();

See this table for the available options:

Setter	Environment variable	Required	Default value
apiKey	ANTHROPIC_API_KEY	false	-
authToken	ANTHROPIC_AUTH_TOKEN	false	-

Tip

Don't create more than one client in the same application. Each client has a connection pool and thread pools, which are more efficient to share between requests.

Requests and responses

To send a request to the Anthropic API, build an instance of some Params class and pass it to the corresponding client method. When the response is received, it will be deserialized into an instance of a Java class.

For example, client.messages().create(...) should be called with an instance of MessageCreateParams, and it will return an instance of Message.

Long requests

Important

We highly encourage you to use streaming for longer running requests.

We do not recommend setting a large maxTokens value without using streaming. Some networks may drop idle connections after a certain period of time, which can cause the request to fail or timeout without receiving a response from Anthropic. We periodically ping the API to keep the connection alive and reduce the impact of these networks.

The SDK throws an error if a non-streaming request is expected to take longer than 10 minutes. Using a streaming method or overriding the timeout at the client or request level disables the error.

Immutability

Each class in the SDK has an associated builder or factory method for constructing it.

Each class is immutable once constructed. If the class has an associated builder, then it has a toBuilder() method, which can be used to convert it back to a builder for making a modified copy.

Because each class is immutable, builder modification will never affect already built class instances.

Asynchronous execution

The default client is synchronous. To switch to asynchronous execution, call the async() method:

import com.anthropic.client.AnthropicClient;
import com.anthropic.client.okhttp.AnthropicOkHttpClient;
import com.anthropic.models.Message;
import com.anthropic.models.MessageCreateParams;
import com.anthropic.models.Model;
import java.util.concurrent.CompletableFuture;

// Configures using the `ANTHROPIC_API_KEY` and `ANTHROPIC_AUTH_TOKEN` environment variables
AnthropicClient client = AnthropicOkHttpClient.fromEnv();

MessageCreateParams params = MessageCreateParams.builder()
    .maxTokens(1024L)
    .addUserMessage("Hello, Claude")
    .model(Model.CLAUDE_3_7_SONNET_LATEST)
    .build();
CompletableFuture<Message> message = client.async().messages().create(params);

Or create an asynchronous client from the beginning:

import com.anthropic.client.AnthropicClientAsync;
import com.anthropic.client.okhttp.AnthropicOkHttpClientAsync;
import com.anthropic.models.Message;
import com.anthropic.models.MessageCreateParams;
import com.anthropic.models.Model;
import java.util.concurrent.CompletableFuture;

// Configures using the `ANTHROPIC_API_KEY` and `ANTHROPIC_AUTH_TOKEN` environment variables
AnthropicClientAsync client = AnthropicOkHttpClientAsync.fromEnv();

MessageCreateParams params = MessageCreateParams.builder()
    .maxTokens(1024L)
    .addUserMessage("Hello, Claude")
    .model(Model.CLAUDE_3_7_SONNET_LATEST)
    .build();
CompletableFuture<Message> message = client.messages().create(params);

The asynchronous client supports the same options as the synchronous one, except most methods return CompletableFutures.

Streaming

The SDK defines methods that return response "chunk" streams, where each chunk can be individually processed as soon as it arrives instead of waiting on the full response. Streaming methods generally correspond to SSE or JSONL responses.

Some of these methods may have streaming and non-streaming variants, but a streaming method will always have a Streaming suffix in its name, even if it doesn't have a non-streaming variant.

These streaming methods return StreamResponse for synchronous clients:

import com.anthropic.core.http.StreamResponse;
import com.anthropic.models.RawMessageStreamEvent;

try (StreamResponse<RawMessageStreamEvent> streamResponse = client.messages().createStreaming(params)) {
    streamResponse.stream().forEach(chunk -> {
        System.out.println(chunk);
    });
    System.out.println("No more chunks!");
}

Or AsyncStreamResponse for asynchronous clients:

import com.anthropic.core.http.AsyncStreamResponse;
import com.anthropic.models.RawMessageStreamEvent;
import java.util.Optional;

client.async().messages().createStreaming(params).subscribe(chunk -> {
    System.out.println(chunk);
});

// If you need to handle errors or completion of the stream
client.async().messages().createStreaming(params).subscribe(new AsyncStreamResponse.Handler<>() {
    @Override
    public void onNext(RawMessageStreamEvent chunk) {
        System.out.println(chunk);
    }

    @Override
    public void onComplete(Optional<Throwable> error) {
        if (error.isPresent()) {
            System.out.println("Something went wrong!");
            throw new RuntimeException(error.get());
        } else {
            System.out.println("No more chunks!");
        }
    }
});

// Or use futures
client.async().messages().createStreaming(params)
    .subscribe(chunk -> {
        System.out.println(chunk);
    })
    .onCompleteFuture();
    .whenComplete((unused, error) -> {
        if (error != null) {
            System.out.println("Something went wrong!");
            throw new RuntimeException(error);
        } else {
            System.out.println("No more chunks!");
        }
    });

Async streaming uses a dedicated per-client cached thread pool Executor to stream without blocking the current thread. This default is suitable for most purposes.

To use a different Executor, configure the subscription using the executor parameter:

import java.util.concurrent.Executor;
import java.util.concurrent.Executors;

Executor executor = Executors.newFixedThreadPool(4);
client.async().messages().createStreaming(params).subscribe(
    chunk -> System.out.println(chunk), executor
);

Or configure the client globally using the streamHandlerExecutor method:

import com.anthropic.client.AnthropicClient;
import com.anthropic.client.okhttp.AnthropicOkHttpClient;
import java.util.concurrent.Executors;

AnthropicClient client = AnthropicOkHttpClient.builder()
    .fromEnv()
    .streamHandlerExecutor(Executors.newFixedThreadPool(4))
    .build();

Raw responses

The SDK defines methods that deserialize responses into instances of Java classes. However, these methods don't provide access to the response headers, status code, or the raw response body.

To access this data, prefix any HTTP method call on a client or service with withRawResponse():

import com.anthropic.core.http.Headers;
import com.anthropic.core.http.HttpResponseFor;
import com.anthropic.models.Message;
import com.anthropic.models.MessageCreateParams;
import com.anthropic.models.Model;

MessageCreateParams params = MessageCreateParams.builder()
    .maxTokens(1024L)
    .addUserMessage("Hello, Claude")
    .model(Model.CLAUDE_3_7_SONNET_LATEST)
    .build();
HttpResponseFor<Message> message = client.messages().withRawResponse().create(params);

int statusCode = message.statusCode();
Headers headers = message.headers();

You can still deserialize the response into an instance of a Java class if needed:

import com.anthropic.models.Message;

Message parsedMessage = message.parse();

Error handling

The SDK throws custom unchecked exception types:

• AnthropicServiceException: Base class for HTTP errors. See this table for which exception subclass is thrown for each HTTP status code:

  Status	Exception
  400	BadRequestException
  401	AuthenticationException
  403	PermissionDeniedException
  404	NotFoundException
  422	UnprocessableEntityException
  429	RateLimitException
  5xx	InternalServerException
  others	UnexpectedStatusCodeException

• AnthropicIoException: I/O networking errors.

• AnthropicInvalidDataException: Failure to interpret successfully parsed data. For example, when accessing a property that's supposed to be required, but the API unexpectedly omitted it from the response.

• AnthropicException: Base class for all exceptions. Most errors will result in one of the previously mentioned ones, but completely generic errors may be thrown using the base class.

Pagination

For methods that return a paginated list of results, this library provides convenient ways access the results either one page at a time, or item-by-item across all pages.

Auto-pagination

To iterate through all results across all pages, you can use autoPager, which automatically handles fetching more pages for you:

Synchronous

import com.anthropic.models.BetaMessageBatch;
import com.anthropic.models.BetaMessageBatchListPage;

// As an Iterable:
BetaMessageBatchListPage page = client.beta().messages().batches().list(params);
for (BetaMessageBatch batch : page.autoPager()) {
    System.out.println(batch);
};

// As a Stream:
client.beta().messages().batches().list(params).autoPager().stream()
    .limit(50)
    .forEach(batch -> System.out.println(batch));

Asynchronous

// Using forEach, which returns CompletableFuture<Void>:
asyncClient.beta().messages().batches().list(params).autoPager()
    .forEach(batch -> System.out.println(batch), executor);

Manual pagination

If none of the above helpers meet your needs, you can also manually request pages one-by-one. A page of results has a data() method to fetch the list of objects, as well as top-level response and other methods to fetch top-level data about the page. It also has methods hasNextPage, getNextPage, and getNextPageParams methods to help with pagination.

import com.anthropic.models.BetaMessageBatch;
import com.anthropic.models.BetaMessageBatchListPage;

BetaMessageBatchListPage page = client.beta().messages().batches().list(params);
while (page != null) {
    for (BetaMessageBatch batch : page.data()) {
        System.out.println(batch);
    }

    page = page.getNextPage().orElse(null);
}

Amazon Bedrock

This SDK also provides support for the Anthropic Bedrock API. This support requires the anthropic-java-bedrock library dependency.

Gradle

implementation("com.anthropic:anthropic-java-bedrock:0.6.0")

Maven

<dependency>
    <groupId>com.anthropic</groupId>
    <artifactId>anthropic-java-bedrock</artifactId>
    <version>0.6.0</version>
</dependency>

Usage

To use Anthropic on Bedrock, create the Anthropic client with the BedrockBackend. Usage of the API is otherwise the same.

import com.anthropic.bedrock.backends.BedrockBackend;
import com.anthropic.client.AnthropicClient;
import com.anthropic.client.okhttp.AnthropicOkHttpClient;

AnthropicClient client = AnthropicOkHttpClient.builder()
        .backend(BedrockBackend.fromEnv())
        .build();

BedrockBackend.fromEnv() automatically resolves the AWS credentials using the AWS default credentials provider chain and resolves the AWS region using the AWS default region provider chain. See those AWS documents for details on how to configure the AWS credentials and AWS region for resolution by those provider chains.

Instead of resolving the AWS credentials and AWS region using the default AWS provider chains, you can resolve them independently using any provider, or any scheme of your choice, and pass them directly to the BedrockBackend during building. For example, you can resolve the AWS credentials directly from environment variables and hard-code the AWS region:

import com.anthropic.bedrock.backends.BedrockBackend;
import com.anthropic.client.AnthropicClient;
import com.anthropic.client.okhttp.AnthropicOkHttpClient;
import software.amazon.awssdk.auth.credentials.AwsBasicCredentials;
import software.amazon.awssdk.auth.credentials.AwsCredentials;
import software.amazon.awssdk.regions.Region;

AwsCredentials awsCredentials = AwsBasicCredentials.create(
        System.getenv("AWS_ACCESS_KEY_ID"),
        System.getenv("AWS_SECRET_ACCESS_KEY"));

AnthropicClient client = AnthropicOkHttpClient.builder()
        .backend(BedrockBackend.builder()
                .awsCredentials(awsCredentials)
                .region(Region.US_EAST_1)
                .build())
        .build();

The AWS classes used above are included automatically as transitive dependencies of the anthropic-java-bedrock library dependency. For other resolution schemes, you may need additional AWS dependencies.

Currently, the Bedrock backend does not support the following:

• Anthropic Batch API
• Anthropic Token Counting API

Google Cloud Vertex AI

This SDK also provides support for Anthropic models on the Google Cloud Vertex AI platform. This support requires the anthropic-java-vertex library dependency.

Gradle

implementation("com.anthropic:anthropic-java-vertex:0.6.0")

Maven

<dependency>
    <groupId>com.anthropic</groupId>
    <artifactId>anthropic-java-vertex</artifactId>
    <version>0.6.0</version>
</dependency>

Usage

To use Anthropic on Vertex AI, create the Anthropic client with the VertexBackend. Usage of the API is otherwise the same.

import com.anthropic.client.AnthropicClient;
import com.anthropic.client.okhttp.AnthropicOkHttpClient;
import com.anthropic.vertex.backends.VertexBackend;

AnthropicClient client = AnthropicOkHttpClient.builder()
        .backend(VertexBackend.fromEnv())
        .build();

VertexBackend.fromEnv() automatically resolves the Google OAuth2 credentials from your configured Google Cloud Application Default Credentials (ADC), the Google Cloud region from the CLOUD_ML_REGION environment variable, and the Google Cloud project ID from ANTHROPIC_VERTEX_PROJECT_ID environment variable. See the Google documentation for details on how to configure your ADC.

Instead of resolving the Google ADC, region and project ID automatically using fromEnv(), you can resolve them independently using an alternative Google Cloud facility, or any scheme of your choice, and pass them directly to the VertexBackend during building. For example, you could resolve the Google credentials and project ID directly from environment variables and hard-code the Google Cloud region:

import com.anthropic.client.AnthropicClient;
import com.anthropic.client.okhttp.AnthropicOkHttpClient;
import com.anthropic.vertex.backends.VertexBackend;
import com.google.auth.oauth2.AccessToken;
import com.google.auth.oauth2.GoogleCredentials;

String accessToken = System.getenv("GOOGLE_APPLICATION_CREDENTIALS");
String project = System.getenv("ANTHROPIC_VERTEX_PROJECT_ID");

GoogleCredentials googleCredentials = GoogleCredentials.create(
        AccessToken.newBuilder().setTokenValue(accessToken).build());

AnthropicClient client = AnthropicOkHttpClient.builder()
        .backend(VertexBackend.builder()
                .googleCredentials(googleCredentials)
                .region("us-central1")
                .project(project)
                .build())
        .build();

The Google Cloud classes used above are included automatically as transitive dependencies of the anthropic-java-vertex library dependency. For other resolution schemes, you may need additional Google Cloud dependencies.

Currently, the Vertex backend does not support the following:

• Anthropic Batch API

Logging

The SDK uses the standard OkHttp logging interceptor.

Enable logging by setting the ANTHROPIC_LOG environment variable to info:

$ export ANTHROPIC_LOG=info

Or to debug for more verbose logging:

$ export ANTHROPIC_LOG=debug

Network options

Retries

The SDK automatically retries 2 times by default, with a short exponential backoff.

Only the following error types are retried:

• Connection errors (for example, due to a network connectivity problem)
• 408 Request Timeout
• 409 Conflict
• 429 Rate Limit
• 5xx Internal

The API may also explicitly instruct the SDK to retry or not retry a response.

To set a custom number of retries, configure the client using the maxRetries method:

import com.anthropic.client.AnthropicClient;
import com.anthropic.client.okhttp.AnthropicOkHttpClient;

AnthropicClient client = AnthropicOkHttpClient.builder()
    .fromEnv()
    .maxRetries(4)
    .build();

Timeouts

Requests time out after 10 minutes by default.

However, for methods that accept maxTokens, if you specify a large maxTokens value and are not streaming, then the default timeout will be calculated dynamically using this formula:

Duration.ofSeconds(
    Math.min(
        60 * 60, // 1 hour max
        Math.max(
            10 * 60, // 10 minute minimum
            60 * 60 * maxTokens / 128_000
        )
    )
)

Which results in a timeout of up to 60 minutes, scaled by the maxTokens parameter, unless overridden.

To set a custom timeout, configure the method call using the timeout method:

import com.anthropic.models.Message;
import com.anthropic.models.MessageCreateParams;
import com.anthropic.models.Model;

Message message = client.messages().create(
  params, RequestOptions.builder().timeout(Duration.ofSeconds(30)).build()
);

Or configure the default for all method calls at the client level:

import com.anthropic.client.AnthropicClient;
import com.anthropic.client.okhttp.AnthropicOkHttpClient;
import java.time.Duration;

AnthropicClient client = AnthropicOkHttpClient.builder()
    .fromEnv()
    .timeout(Duration.ofSeconds(30))
    .build();

Proxies

To route requests through a proxy, configure the client using the proxy method:

import com.anthropic.client.AnthropicClient;
import com.anthropic.client.okhttp.AnthropicOkHttpClient;
import java.net.InetSocketAddress;
import java.net.Proxy;

AnthropicClient client = AnthropicOkHttpClient.builder()
    .fromEnv()
    .proxy(new Proxy(
      Proxy.Type.HTTP, new InetSocketAddress(
        "https://example.com", 8080
      )
    ))
    .build();

Undocumented API functionality

The SDK is typed for convenient usage of the documented API. However, it also supports working with undocumented or not yet supported parts of the API.

Parameters

To set undocumented parameters, call the putAdditionalHeader, putAdditionalQueryParam, or putAdditionalBodyProperty methods on any Params class:

import com.anthropic.core.JsonValue;
import com.anthropic.models.MessageCreateParams;

MessageCreateParams params = MessageCreateParams.builder()
    .putAdditionalHeader("Secret-Header", "42")
    .putAdditionalQueryParam("secret_query_param", "42")
    .putAdditionalBodyProperty("secretProperty", JsonValue.from("42"))
    .build();

These can be accessed on the built object later using the _additionalHeaders(), _additionalQueryParams(), and _additionalBodyProperties() methods. You can also set undocumented parameters on nested headers, query params, or body classes using the putAdditionalProperty method. These properties can be accessed on the built object later using the _additionalProperties() method.

To set a documented parameter or property to an undocumented or not yet supported value, pass a JsonValue object to its setter:

import com.anthropic.core.JsonValue;
import com.anthropic.models.MessageCreateParams;
import com.anthropic.models.Model;

MessageCreateParams params = MessageCreateParams.builder()
    .maxTokens(JsonValue.from(3.14))
    .addUserMessage("Hello, Claude")
    .model(Model.CLAUDE_3_7_SONNET_LATEST)
    .build();

Response properties

To access undocumented response properties, call the _additionalProperties() method:

import com.anthropic.core.JsonValue;
import java.util.Map;

Map<String, JsonValue> additionalProperties = client.messages().create(params)._additionalProperties();
JsonValue secretPropertyValue = additionalProperties.get("secretProperty");

String result = secretPropertyValue.accept(new JsonValue.Visitor<>() {
    @Override
    public String visitNull() {
        return "It's null!";
    }

    @Override
    public String visitBoolean(boolean value) {
        return "It's a boolean!";
    }

    @Override
    public String visitNumber(Number value) {
        return "It's a number!";
    }

    // Other methods include `visitMissing`, `visitString`, `visitArray`, and `visitObject`
    // The default implementation of each unimplemented method delegates to `visitDefault`, which throws by default, but can also be overridden
});

To access a property's raw JSON value, which may be undocumented, call its _ prefixed method:

import com.anthropic.core.JsonField;
import java.util.Optional;

JsonField<Long> maxTokens = client.messages().create(params)._maxTokens();

if (maxTokens.isMissing()) {
  // The property is absent from the JSON response
} else if (maxTokens.isNull()) {
  // The property was set to literal null
} else {
  // Check if value was provided as a string
  // Other methods include `asNumber()`, `asBoolean()`, etc.
  Optional<String> jsonString = maxTokens.asString();

  // Try to deserialize into a custom type
  MyClass myObject = maxTokens.asUnknown().orElseThrow().convert(MyClass.class);
}

Response validation

In rare cases, the API may return a response that doesn't match the expected type. For example, the SDK may expect a property to contain a String, but the API could return something else.

By default, the SDK will not throw an exception in this case. It will throw AnthropicInvalidDataException only if you directly access the property.

If you would prefer to check that the response is completely well-typed upfront, then either call validate():

import com.anthropic.models.Message;

Message message = client.messages().create(params).validate();

Or configure the method call to validate the response using the responseValidation method:

import com.anthropic.models.Message;
import com.anthropic.models.MessageCreateParams;
import com.anthropic.models.Model;

Message message = client.messages().create(
  params, RequestOptions.builder().responseValidation(true).build()
);

Or configure the default for all method calls at the client level:

import com.anthropic.client.AnthropicClient;
import com.anthropic.client.okhttp.AnthropicOkHttpClient;

AnthropicClient client = AnthropicOkHttpClient.builder()
    .fromEnv()
    .responseValidation(true)
    .build();

FAQ

Why don't you use plain enum classes?

Java enum classes are not trivially forwards compatible. Using them in the SDK could cause runtime exceptions if the API is updated to respond with a new enum value.

Why do you represent fields using JsonField<T> instead of just plain T?

Using JsonField<T> enables a few features:

• Allowing usage of undocumented API functionality
• Lazily validating the API response against the expected shape
• Representing absent vs explicitly null values

Why don't you use data classes?

It is not backwards compatible to add new fields to a data class and we don't want to introduce a breaking change every time we add a field to a class.

Why don't you use checked exceptions?

Checked exceptions are widely considered a mistake in the Java programming language. In fact, they were omitted from Kotlin for this reason.

Checked exceptions:

• Are verbose to handle
• Encourage error handling at the wrong level of abstraction, where nothing can be done about the error
• Are tedious to propagate due to the function coloring problem
• Don't play well with lambdas (also due to the function coloring problem)

Semantic versioning

This package generally follows SemVer conventions, though certain backwards-incompatible changes may be released as minor versions:

1. Changes to library internals which are technically public but not intended or documented for external use. (Please open a GitHub issue to let us know if you are relying on such internals.)
2. Changes that we do not expect to impact the vast majority of users in practice.

We take backwards-compatibility seriously and work hard to ensure you can rely on a smooth upgrade experience.

We are keen for your feedback; please open an issue with questions, bugs, or suggestions.