Finch Java API Library

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

The Finch Java SDK is similar to the Finch Kotlin SDK but with minor differences that make it more ergonomic for use in Java, such as Optional instead of nullable values, Stream instead of Sequence, and CompletableFuture instead of suspend functions.

It is generated with Stainless.

The REST API documentation can be found on developer.tryfinch.com. Javadocs are available on javadoc.io.

Installation

Gradle

implementation("com.tryfinch.api:finch-java:7.2.0")

Maven

<dependency>
  <groupId>com.tryfinch.api</groupId>
  <artifactId>finch-java</artifactId>
  <version>7.2.0</version>
</dependency>

Requirements

This library requires Java 8 or later.

Usage

import com.tryfinch.api.client.FinchClient;
import com.tryfinch.api.client.okhttp.FinchOkHttpClient;
import com.tryfinch.api.models.HrisDirectoryListPage;
import com.tryfinch.api.models.HrisDirectoryListParams;

FinchClient client = FinchOkHttpClient.builder()
    // Configures using the `FINCH_CLIENT_ID`, `FINCH_CLIENT_SECRET`, `FINCH_WEBHOOK_SECRET` and `FINCH_BASE_URL` environment variables
    .fromEnv()
    .accessToken("My Access Token")
    .build();

HrisDirectoryListPage page = client.hris().directory().list();

Client configuration

Configure the client using environment variables:

import com.tryfinch.api.client.FinchClient;
import com.tryfinch.api.client.okhttp.FinchOkHttpClient;

FinchClient client = FinchOkHttpClient.builder()
    // Configures using the `FINCH_CLIENT_ID`, `FINCH_CLIENT_SECRET`, `FINCH_WEBHOOK_SECRET` and `FINCH_BASE_URL` environment variables
    .fromEnv()
    .accessToken("My Access Token")
    .build();

Or manually:

import com.tryfinch.api.client.FinchClient;
import com.tryfinch.api.client.okhttp.FinchOkHttpClient;

FinchClient client = FinchOkHttpClient.builder()
    .accessToken("My Access Token")
    .build();

Or using a combination of the two approaches:

import com.tryfinch.api.client.FinchClient;
import com.tryfinch.api.client.okhttp.FinchOkHttpClient;

FinchClient client = FinchOkHttpClient.builder()
    // Configures using the `FINCH_CLIENT_ID`, `FINCH_CLIENT_SECRET`, `FINCH_WEBHOOK_SECRET` and `FINCH_BASE_URL` environment variables
    .fromEnv()
    .accessToken("My Access Token")
    .build();

See this table for the available options:

Setter	Environment variable	Required	Default value
`clientId`	`FINCH_CLIENT_ID`	false	-
`clientSecret`	`FINCH_CLIENT_SECRET`	false	-
`webhookSecret`	`FINCH_WEBHOOK_SECRET`	false	-
`baseUrl`	`FINCH_BASE_URL`	true	`"https://api.tryfinch.com"`

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 Finch 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.hris().directory().list(...) should be called with an instance of HrisDirectoryListParams, and it will return an instance of HrisDirectoryListPage.

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.tryfinch.api.client.FinchClient;
import com.tryfinch.api.client.okhttp.FinchOkHttpClient;
import com.tryfinch.api.models.HrisDirectoryListPageAsync;
import com.tryfinch.api.models.HrisDirectoryListParams;
import java.util.concurrent.CompletableFuture;

FinchClient client = FinchOkHttpClient.builder()
    // Configures using the `FINCH_CLIENT_ID`, `FINCH_CLIENT_SECRET`, `FINCH_WEBHOOK_SECRET` and `FINCH_BASE_URL` environment variables
    .fromEnv()
    .accessToken("My Access Token")
    .build();

CompletableFuture<HrisDirectoryListPageAsync> page = client.async().hris().directory().list();

Or create an asynchronous client from the beginning:

import com.tryfinch.api.client.FinchClientAsync;
import com.tryfinch.api.client.okhttp.FinchOkHttpClientAsync;
import com.tryfinch.api.models.HrisDirectoryListPageAsync;
import com.tryfinch.api.models.HrisDirectoryListParams;
import java.util.concurrent.CompletableFuture;

FinchClientAsync client = FinchOkHttpClientAsync.builder()
    // Configures using the `FINCH_CLIENT_ID`, `FINCH_CLIENT_SECRET`, `FINCH_WEBHOOK_SECRET` and `FINCH_BASE_URL` environment variables
    .fromEnv()
    .accessToken("My Access Token")
    .build();

CompletableFuture<HrisDirectoryListPageAsync> page = client.hris().directory().list();

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

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.tryfinch.api.core.http.Headers;
import com.tryfinch.api.core.http.HttpResponseFor;
import com.tryfinch.api.models.HrisDirectoryListPage;
import com.tryfinch.api.models.HrisDirectoryListParams;

HttpResponseFor<HrisDirectoryListPage> page = client.hris().directory().withRawResponse().list();

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

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

import com.tryfinch.api.models.HrisDirectoryListPage;

HrisDirectoryListPage parsedPage = page.parse();

Error handling

The SDK throws custom unchecked exception types:

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

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

FinchIoException: I/O networking errors.
FinchInvalidDataException: 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.
FinchException: 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

The SDK defines methods that return a paginated lists of results. It provides convenient ways to 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, use the autoPager() method, which automatically fetches more pages as needed.

When using the synchronous client, the method returns an Iterable

import com.tryfinch.api.models.HrisDirectoryListPage;
import com.tryfinch.api.models.IndividualInDirectory;

HrisDirectoryListPage page = client.hris().directory().list();

// Process as an Iterable
for (IndividualInDirectory directory : page.autoPager()) {
    System.out.println(directory);
}

// Process as a Stream
page.autoPager()
    .stream()
    .limit(50)
    .forEach(directory -> System.out.println(directory));

When using the asynchronous client, the method returns an AsyncStreamResponse:

import com.tryfinch.api.core.http.AsyncStreamResponse;
import com.tryfinch.api.models.HrisDirectoryListPageAsync;
import com.tryfinch.api.models.IndividualInDirectory;
import java.util.Optional;
import java.util.concurrent.CompletableFuture;

CompletableFuture<HrisDirectoryListPageAsync> pageFuture = client.async().hris().directory().list();

pageFuture.thenRun(page -> page.autoPager().subscribe(directory -> {
    System.out.println(directory);
}));

// If you need to handle errors or completion of the stream
pageFuture.thenRun(page -> page.autoPager().subscribe(new AsyncStreamResponse.Handler<>() {
    @Override
    public void onNext(IndividualInDirectory directory) {
        System.out.println(directory);
    }

    @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!");
        }
    }
}));

// Or use futures
pageFuture.thenRun(page -> page.autoPager()
    .subscribe(directory -> {
        System.out.println(directory);
    })
    .onCompleteFuture()
    .whenComplete((unused, error) -> {
        if (error != null) {
            System.out.println("Something went wrong!");
            throw new RuntimeException(error);
        } else {
            System.out.println("No more!");
        }
    }));

Manual pagination

To access individual page items and manually request the next page, use the items(), hasNextPage(), and nextPage() methods:

import com.tryfinch.api.models.HrisDirectoryListPage;
import com.tryfinch.api.models.IndividualInDirectory;

HrisDirectoryListPage page = client.hris().directory().list();
while (true) {
    for (IndividualInDirectory directory : page.items()) {
        System.out.println(directory);
    }

    if (!page.hasNextPage()) {
        break;
    }

    page = page.nextPage();
}

Logging

The SDK uses the standard OkHttp logging interceptor.

Enable logging by setting the FINCH_LOG environment variable to info:

$ export FINCH_LOG=info

Or to debug for more verbose logging:

$ export FINCH_LOG=debug

Webhook Verification

We provide helper methods for verifying that a webhook request came from Finch, and not a malicious third party.

You can use finch.webhooks().verifySignature(body, headers, secret?) or finch.webhooks().unwrap(body, headers, secret?), both of which will raise an error if the signature is invalid.

Note that the "body" parameter must be the raw JSON string sent from the server (do not parse it first). The .unwrap() method can parse this JSON for you.

Jackson

The SDK depends on Jackson for JSON serialization/deserialization. It is compatible with version 2.13.4 or higher, but depends on version 2.18.2 by default.

The SDK throws an exception if it detects an incompatible Jackson version at runtime (e.g. if the default version was overridden in your Maven or Gradle config).

If the SDK threw an exception, but you're certain the version is compatible, then disable the version check using the checkJacksonVersionCompatibility on FinchOkHttpClient or FinchOkHttpClientAsync.

Caution

We make no guarantee that the SDK works correctly when the Jackson version check is disabled.

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.tryfinch.api.client.FinchClient;
import com.tryfinch.api.client.okhttp.FinchOkHttpClient;

FinchClient client = FinchOkHttpClient.builder()
    .fromEnv()
    .maxRetries(4)
    .accessToken("My Access Token")
    .build();

Timeouts

Requests time out after 1 minute by default.

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

import com.tryfinch.api.models.HrisDirectoryListPage;

HrisDirectoryListPage page = client.hris().directory().list(RequestOptions.builder().timeout(Duration.ofSeconds(30)).build());

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

import com.tryfinch.api.client.FinchClient;
import com.tryfinch.api.client.okhttp.FinchOkHttpClient;
import java.time.Duration;

FinchClient client = FinchOkHttpClient.builder()
    .fromEnv()
    .timeout(Duration.ofSeconds(30))
    .accessToken("My Access Token")
    .build();

Proxies

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

import com.tryfinch.api.client.FinchClient;
import com.tryfinch.api.client.okhttp.FinchOkHttpClient;
import java.net.InetSocketAddress;
import java.net.Proxy;

FinchClient client = FinchOkHttpClient.builder()
    .fromEnv()
    .proxy(new Proxy(
      Proxy.Type.HTTP, new InetSocketAddress(
        "https://example.com", 8080
      )
    ))
    .accessToken("My Access Token")
    .build();

Custom HTTP client

The SDK consists of three artifacts:

finch-java-core
- Contains core SDK logic
- Does not depend on OkHttp
- Exposes FinchClient, FinchClientAsync, FinchClientImpl, and FinchClientAsyncImpl, all of which can work with any HTTP client
finch-java-client-okhttp
- Depends on OkHttp
- Exposes FinchOkHttpClient and FinchOkHttpClientAsync, which provide a way to construct FinchClientImpl and FinchClientAsyncImpl, respectively, using OkHttp
finch-java
- Depends on and exposes the APIs of both finch-java-core and finch-java-client-okhttp
- Does not have its own logic

This structure allows replacing the SDK's default HTTP client without pulling in unnecessary dependencies.

Customized `OkHttpClient`

Tip

Try the available network options before replacing the default client.

To use a customized OkHttpClient:

Replace your finch-java dependency with finch-java-core
Copy finch-java-client-okhttp's OkHttpClient class into your code and customize it
Construct FinchClientImpl or FinchClientAsyncImpl, similarly to FinchOkHttpClient or FinchOkHttpClientAsync, using your customized client

Completely custom HTTP client

To use a completely custom HTTP client:

Replace your finch-java dependency with finch-java-core
Write a class that implements the HttpClient interface
Construct FinchClientImpl or FinchClientAsyncImpl, similarly to FinchOkHttpClient or FinchOkHttpClientAsync, using your new client class

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.tryfinch.api.core.JsonValue;
import com.tryfinch.api.models.HrisDirectoryListParams;

HrisDirectoryListParams params = HrisDirectoryListParams.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.

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

import com.tryfinch.api.models.HrisDirectoryListParams;

HrisDirectoryListParams params = HrisDirectoryListParams.builder().build();

The most straightforward way to create a JsonValue is using its from(...) method:

import com.tryfinch.api.core.JsonValue;
import java.util.List;
import java.util.Map;

// Create primitive JSON values
JsonValue nullValue = JsonValue.from(null);
JsonValue booleanValue = JsonValue.from(true);
JsonValue numberValue = JsonValue.from(42);
JsonValue stringValue = JsonValue.from("Hello World!");

// Create a JSON array value equivalent to `["Hello", "World"]`
JsonValue arrayValue = JsonValue.from(List.of(
  "Hello", "World"
));

// Create a JSON object value equivalent to `{ "a": 1, "b": 2 }`
JsonValue objectValue = JsonValue.from(Map.of(
  "a", 1,
  "b", 2
));

// Create an arbitrarily nested JSON equivalent to:
// {
//   "a": [1, 2],
//   "b": [3, 4]
// }
JsonValue complexValue = JsonValue.from(Map.of(
  "a", List.of(
    1, 2
  ),
  "b", List.of(
    3, 4
  )
));

Normally a Builder class's build method will throw IllegalStateException if any required parameter or property is unset.

To forcibly omit a required parameter or property, pass JsonMissing:

import com.tryfinch.api.core.JsonMissing;
import com.tryfinch.api.models.AccessTokenCreateParams;
import com.tryfinch.api.models.HrisDirectoryListParams;

HrisDirectoryListParams params = AccessTokenCreateParams.builder()
    .code(JsonMissing.of())
    .build();

Response properties

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

import com.tryfinch.api.core.JsonValue;
import java.util.Map;

Map<String, JsonValue> additionalProperties = client.accessTokens().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.tryfinch.api.core.JsonField;
import java.util.Optional;

JsonField<String> code = client.accessTokens().create(params)._code();

if (code.isMissing()) {
  // The property is absent from the JSON response
} else if (code.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 = code.asString();

  // Try to deserialize into a custom type
  MyClass myObject = code.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 FinchInvalidDataException 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.tryfinch.api.models.CreateAccessTokenResponse;

CreateAccessTokenResponse createAccessTokenResponse = client.accessTokens().create(params).validate();

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

import com.tryfinch.api.models.HrisDirectoryListPage;

HrisDirectoryListPage page = client.hris().directory().list(RequestOptions.builder().responseValidation(true).build());

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

import com.tryfinch.api.client.FinchClient;
import com.tryfinch.api.client.okhttp.FinchOkHttpClient;

FinchClient client = FinchOkHttpClient.builder()
    .fromEnv()
    .responseValidation(true)
    .accessToken("My Access Token")
    .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:

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.)
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.

Name		Name	Last commit message	Last commit date
Latest commit History 430 Commits
.devcontainer		.devcontainer
.github/workflows		.github/workflows
bin		bin
buildSrc		buildSrc
examples		examples
finch-java-client-okhttp		finch-java-client-okhttp
finch-java-core		finch-java-core
finch-java-example		finch-java-example
finch-java-lib		finch-java-lib
finch-java		finch-java
gradle/wrapper		gradle/wrapper
scripts		scripts
.gitattributes		.gitattributes
.gitignore		.gitignore
.release-please-manifest.json		.release-please-manifest.json
.stats.yml		.stats.yml
CHANGELOG.md		CHANGELOG.md
CODEOWNERS		CODEOWNERS
LICENSE		LICENSE
README.md		README.md
SECURITY.md		SECURITY.md
build.gradle.kts		build.gradle.kts
gradle.properties		gradle.properties
gradlew		gradlew
gradlew.bat		gradlew.bat
release-please-config.json		release-please-config.json
settings.gradle.kts		settings.gradle.kts

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Finch-API/finch-api-java

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Finch Java API Library

Installation

Gradle

Maven

Requirements

Usage

Client configuration

Requests and responses

Immutability

Asynchronous execution

Raw responses

Error handling

Pagination

Auto-pagination

Manual pagination

Logging

Webhook Verification

Jackson

Network options

Retries

Timeouts

Proxies

Custom HTTP client

Customized OkHttpClient

Completely custom HTTP client

Undocumented API functionality

Parameters

Response properties

Response validation

FAQ

Why don't you use plain enum classes?

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

Why don't you use data classes?

Why don't you use checked exceptions?

Semantic versioning

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