Onebusaway SDK Java API Library

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

The Onebusaway SDK Java SDK is similar to the Onebusaway SDK 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.onebusaway.org. Javadocs are available on javadoc.io.

Installation

Gradle

implementation("org.onebusaway:onebusaway-sdk-java:0.1.0-alpha.27")

Maven

<dependency>
  <groupId>org.onebusaway</groupId>
  <artifactId>onebusaway-sdk-java</artifactId>
  <version>0.1.0-alpha.27</version>
</dependency>

Requirements

This library requires Java 8 or later.

Usage

import org.onebusaway.client.OnebusawaySdkClient;
import org.onebusaway.client.okhttp.OnebusawaySdkOkHttpClient;
import org.onebusaway.models.currenttime.CurrentTimeRetrieveParams;
import org.onebusaway.models.currenttime.CurrentTimeRetrieveResponse;

// Configures using the `ONEBUSAWAY_API_KEY` and `ONEBUSAWAY_SDK_BASE_URL` environment variables
OnebusawaySdkClient client = OnebusawaySdkOkHttpClient.fromEnv();

CurrentTimeRetrieveResponse currentTime = client.currentTime().retrieve();

Client configuration

Configure the client using environment variables:

import org.onebusaway.client.OnebusawaySdkClient;
import org.onebusaway.client.okhttp.OnebusawaySdkOkHttpClient;

// Configures using the `ONEBUSAWAY_API_KEY` and `ONEBUSAWAY_SDK_BASE_URL` environment variables
OnebusawaySdkClient client = OnebusawaySdkOkHttpClient.fromEnv();

Or manually:

import org.onebusaway.client.OnebusawaySdkClient;
import org.onebusaway.client.okhttp.OnebusawaySdkOkHttpClient;

OnebusawaySdkClient client = OnebusawaySdkOkHttpClient.builder()
    .apiKey("My API Key")
    .build();

Or using a combination of the two approaches:

import org.onebusaway.client.OnebusawaySdkClient;
import org.onebusaway.client.okhttp.OnebusawaySdkOkHttpClient;

OnebusawaySdkClient client = OnebusawaySdkOkHttpClient.builder()
    // Configures using the `ONEBUSAWAY_API_KEY` and `ONEBUSAWAY_SDK_BASE_URL` environment variables
    .fromEnv()
    .apiKey("My API Key")
    .build();

See this table for the available options:

Setter	Environment variable	Required	Default value
apiKey	ONEBUSAWAY_API_KEY	true	-
baseUrl	ONEBUSAWAY_SDK_BASE_URL	true	"https://api.pugetsound.onebusaway.org"

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.

Modifying configuration

To temporarily use a modified client configuration, while reusing the same connection and thread pools, call withOptions() on any client or service:

import org.onebusaway.client.OnebusawaySdkClient;

OnebusawaySdkClient clientWithOptions = client.withOptions(optionsBuilder -> {
    optionsBuilder.baseUrl("https://example.com");
    optionsBuilder.maxRetries(42);
});

The withOptions() method does not affect the original client or service.

Requests and responses

To send a request to the Onebusaway SDK 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.currentTime().retrieve(...) should be called with an instance of CurrentTimeRetrieveParams, and it will return an instance of CurrentTimeRetrieveResponse.

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 java.util.concurrent.CompletableFuture;
import org.onebusaway.client.OnebusawaySdkClient;
import org.onebusaway.client.okhttp.OnebusawaySdkOkHttpClient;
import org.onebusaway.models.currenttime.CurrentTimeRetrieveParams;
import org.onebusaway.models.currenttime.CurrentTimeRetrieveResponse;

// Configures using the `ONEBUSAWAY_API_KEY` and `ONEBUSAWAY_SDK_BASE_URL` environment variables
OnebusawaySdkClient client = OnebusawaySdkOkHttpClient.fromEnv();

CompletableFuture<CurrentTimeRetrieveResponse> currentTime = client.async().currentTime().retrieve();

Or create an asynchronous client from the beginning:

import java.util.concurrent.CompletableFuture;
import org.onebusaway.client.OnebusawaySdkClientAsync;
import org.onebusaway.client.okhttp.OnebusawaySdkOkHttpClientAsync;
import org.onebusaway.models.currenttime.CurrentTimeRetrieveParams;
import org.onebusaway.models.currenttime.CurrentTimeRetrieveResponse;

// Configures using the `ONEBUSAWAY_API_KEY` and `ONEBUSAWAY_SDK_BASE_URL` environment variables
OnebusawaySdkClientAsync client = OnebusawaySdkOkHttpClientAsync.fromEnv();

CompletableFuture<CurrentTimeRetrieveResponse> currentTime = client.currentTime().retrieve();

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 org.onebusaway.core.http.Headers;
import org.onebusaway.core.http.HttpResponseFor;
import org.onebusaway.models.currenttime.CurrentTimeRetrieveParams;
import org.onebusaway.models.currenttime.CurrentTimeRetrieveResponse;

HttpResponseFor<CurrentTimeRetrieveResponse> currentTime = client.currentTime().withRawResponse().retrieve();

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

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

import org.onebusaway.models.currenttime.CurrentTimeRetrieveResponse;

CurrentTimeRetrieveResponse parsedCurrentTime = currentTime.parse();

Error handling

The SDK throws custom unchecked exception types:

• OnebusawaySdkServiceException: 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

• OnebusawaySdkIoException: I/O networking errors.

• OnebusawaySdkInvalidDataException: 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.

• OnebusawaySdkException: 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.

Logging

The SDK uses the standard OkHttp logging interceptor.

Enable logging by setting the ONEBUSAWAY_SDK_LOG environment variable to info:

$ export ONEBUSAWAY_SDK_LOG=info

Or to debug for more verbose logging:

$ export ONEBUSAWAY_SDK_LOG=debug

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 OnebusawaySdkOkHttpClient or OnebusawaySdkOkHttpClientAsync.

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 org.onebusaway.client.OnebusawaySdkClient;
import org.onebusaway.client.okhttp.OnebusawaySdkOkHttpClient;

OnebusawaySdkClient client = OnebusawaySdkOkHttpClient.builder()
    .fromEnv()
    .maxRetries(4)
    .build();

Timeouts

Requests time out after 1 minute by default.

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

import org.onebusaway.models.currenttime.CurrentTimeRetrieveResponse;

CurrentTimeRetrieveResponse currentTime = client.currentTime().retrieve(RequestOptions.builder().timeout(Duration.ofSeconds(30)).build());

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

import java.time.Duration;
import org.onebusaway.client.OnebusawaySdkClient;
import org.onebusaway.client.okhttp.OnebusawaySdkOkHttpClient;

OnebusawaySdkClient client = OnebusawaySdkOkHttpClient.builder()
    .fromEnv()
    .timeout(Duration.ofSeconds(30))
    .build();

Proxies

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

import java.net.InetSocketAddress;
import java.net.Proxy;
import org.onebusaway.client.OnebusawaySdkClient;
import org.onebusaway.client.okhttp.OnebusawaySdkOkHttpClient;

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

Custom HTTP client

The SDK consists of three artifacts:

• onebusaway-sdk-java-core
  • Contains core SDK logic
  • Does not depend on OkHttp
  • Exposes OnebusawaySdkClient, OnebusawaySdkClientAsync, OnebusawaySdkClientImpl, and OnebusawaySdkClientAsyncImpl, all of which can work with any HTTP client
• onebusaway-sdk-java-client-okhttp
  • Depends on OkHttp
  • Exposes OnebusawaySdkOkHttpClient and OnebusawaySdkOkHttpClientAsync, which provide a way to construct OnebusawaySdkClientImpl and OnebusawaySdkClientAsyncImpl, respectively, using OkHttp
• onebusaway-sdk-java
  • Depends on and exposes the APIs of both onebusaway-sdk-java-core and onebusaway-sdk-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:

1. Replace your onebusaway-sdk-java dependency with onebusaway-sdk-java-core
2. Copy onebusaway-sdk-java-client-okhttp's OkHttpClient class into your code and customize it
3. Construct OnebusawaySdkClientImpl or OnebusawaySdkClientAsyncImpl, similarly to OnebusawaySdkOkHttpClient or OnebusawaySdkOkHttpClientAsync, using your customized client

Completely custom HTTP client

To use a completely custom HTTP client:

1. Replace your onebusaway-sdk-java dependency with onebusaway-sdk-java-core
2. Write a class that implements the HttpClient interface
3. Construct OnebusawaySdkClientImpl or OnebusawaySdkClientAsyncImpl, similarly to OnebusawaySdkOkHttpClient or OnebusawaySdkOkHttpClientAsync, 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 org.onebusaway.core.JsonValue;
import org.onebusaway.models.currenttime.CurrentTimeRetrieveParams;

CurrentTimeRetrieveParams params = CurrentTimeRetrieveParams.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 org.onebusaway.models.currenttime.CurrentTimeRetrieveParams;

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

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

import java.util.List;
import java.util.Map;
import org.onebusaway.core.JsonValue;

// 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 org.onebusaway.core.JsonMissing;
import org.onebusaway.models.agency.AgencyRetrieveParams;
import org.onebusaway.models.currenttime.CurrentTimeRetrieveParams;

CurrentTimeRetrieveParams params = AgencyRetrieveParams.builder()
    .agencyId(JsonMissing.of())
    .build();

Response properties

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

import java.util.Map;
import org.onebusaway.core.JsonValue;

Map<String, JsonValue> additionalProperties = client.currentTime().retrieve(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 java.util.Optional;
import org.onebusaway.core.JsonField;

JsonField<Object> field = client.currentTime().retrieve(params)._field();

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

  // Try to deserialize into a custom type
  MyClass myObject = field.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 OnebusawaySdkInvalidDataException 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 org.onebusaway.models.currenttime.CurrentTimeRetrieveResponse;

CurrentTimeRetrieveResponse currentTime = client.currentTime().retrieve(params).validate();

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

import org.onebusaway.models.currenttime.CurrentTimeRetrieveResponse;

CurrentTimeRetrieveResponse currentTime = client.currentTime().retrieve(RequestOptions.builder().responseValidation(true).build());

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

import org.onebusaway.client.OnebusawaySdkClient;
import org.onebusaway.client.okhttp.OnebusawaySdkOkHttpClient;

OnebusawaySdkClient client = OnebusawaySdkOkHttpClient.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.