Cas Parser Java API Library

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

It is generated with Stainless.

The REST API documentation can be found on docs.casparser.in. Javadocs are available on javadoc.io.

Installation

Gradle

implementation("com.cas_parser.api:cas-parser-java:0.0.2")

Maven

<dependency>
  <groupId>com.cas_parser.api</groupId>
  <artifactId>cas-parser-java</artifactId>
  <version>0.0.2</version>
</dependency>

Requirements

This library requires Java 8 or later.

Usage

import com.cas_parser.api.client.CasParserClient;
import com.cas_parser.api.client.okhttp.CasParserOkHttpClient;
import com.cas_parser.api.models.casparser.CasParserSmartParseParams;
import com.cas_parser.api.models.casparser.UnifiedResponse;

// Configures using the `casparser.apiKey` and `casparser.baseUrl` system properties
// Or configures using the `CAS_PARSER_API_KEY` and `CAS_PARSER_BASE_URL` environment variables
CasParserClient client = CasParserOkHttpClient.fromEnv();

CasParserSmartParseParams params = CasParserSmartParseParams.builder()
    .password("ABCDF")
    .pdfUrl("https://your-cas-pdf-url-here.com")
    .build();
UnifiedResponse unifiedResponse = client.casParser().smartParse(params);

Client configuration

Configure the client using system properties or environment variables:

import com.cas_parser.api.client.CasParserClient;
import com.cas_parser.api.client.okhttp.CasParserOkHttpClient;

// Configures using the `casparser.apiKey` and `casparser.baseUrl` system properties
// Or configures using the `CAS_PARSER_API_KEY` and `CAS_PARSER_BASE_URL` environment variables
CasParserClient client = CasParserOkHttpClient.fromEnv();

Or manually:

import com.cas_parser.api.client.CasParserClient;
import com.cas_parser.api.client.okhttp.CasParserOkHttpClient;

CasParserClient client = CasParserOkHttpClient.builder()
    .apiKey("My API Key")
    .build();

Or using a combination of the two approaches:

import com.cas_parser.api.client.CasParserClient;
import com.cas_parser.api.client.okhttp.CasParserOkHttpClient;

CasParserClient client = CasParserOkHttpClient.builder()
    // Configures using the `casparser.apiKey` and `casparser.baseUrl` system properties
    // Or configures using the `CAS_PARSER_API_KEY` and `CAS_PARSER_BASE_URL` environment variables
    .fromEnv()
    .apiKey("My API Key")
    .build();

See this table for the available options:

Setter	System property	Environment variable	Required	Default value
`apiKey`	`casparser.apiKey`	`CAS_PARSER_API_KEY`	true	-
`baseUrl`	`casparser.baseUrl`	`CAS_PARSER_BASE_URL`	true	`"https://portfolio-parser.api.casparser.in"`

System properties take precedence over environment variables.

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 com.cas_parser.api.client.CasParserClient;

CasParserClient 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 Cas Parser 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.casParser().smartParse(...) should be called with an instance of CasParserSmartParseParams, and it will return an instance of UnifiedResponse.

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.cas_parser.api.client.CasParserClient;
import com.cas_parser.api.client.okhttp.CasParserOkHttpClient;
import com.cas_parser.api.models.casparser.CasParserSmartParseParams;
import com.cas_parser.api.models.casparser.UnifiedResponse;
import java.util.concurrent.CompletableFuture;

// Configures using the `casparser.apiKey` and `casparser.baseUrl` system properties
// Or configures using the `CAS_PARSER_API_KEY` and `CAS_PARSER_BASE_URL` environment variables
CasParserClient client = CasParserOkHttpClient.fromEnv();

CasParserSmartParseParams params = CasParserSmartParseParams.builder()
    .password("ABCDF")
    .pdfUrl("https://your-cas-pdf-url-here.com")
    .build();
CompletableFuture<UnifiedResponse> unifiedResponse = client.async().casParser().smartParse(params);

Or create an asynchronous client from the beginning:

import com.cas_parser.api.client.CasParserClientAsync;
import com.cas_parser.api.client.okhttp.CasParserOkHttpClientAsync;
import com.cas_parser.api.models.casparser.CasParserSmartParseParams;
import com.cas_parser.api.models.casparser.UnifiedResponse;
import java.util.concurrent.CompletableFuture;

// Configures using the `casparser.apiKey` and `casparser.baseUrl` system properties
// Or configures using the `CAS_PARSER_API_KEY` and `CAS_PARSER_BASE_URL` environment variables
CasParserClientAsync client = CasParserOkHttpClientAsync.fromEnv();

CasParserSmartParseParams params = CasParserSmartParseParams.builder()
    .password("ABCDF")
    .pdfUrl("https://your-cas-pdf-url-here.com")
    .build();
CompletableFuture<UnifiedResponse> unifiedResponse = client.casParser().smartParse(params);

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.cas_parser.api.core.http.Headers;
import com.cas_parser.api.core.http.HttpResponseFor;
import com.cas_parser.api.models.casparser.CasParserSmartParseParams;
import com.cas_parser.api.models.casparser.UnifiedResponse;

CasParserSmartParseParams params = CasParserSmartParseParams.builder()
    .password("ABCDF")
    .pdfUrl("https://you-cas-pdf-url-here.com")
    .build();
HttpResponseFor<UnifiedResponse> unifiedResponse = client.casParser().withRawResponse().smartParse(params);

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

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

import com.cas_parser.api.models.casparser.UnifiedResponse;

UnifiedResponse parsedUnifiedResponse = unifiedResponse.parse();

Error handling

The SDK throws custom unchecked exception types:

CasParserServiceException: 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`

CasParserIoException: I/O networking errors.
CasParserRetryableException: Generic error indicating a failure that could be retried by the client.
CasParserInvalidDataException: 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.
CasParserException: 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 CAS_PARSER_LOG environment variable to info:

$ export CAS_PARSER_LOG=info

Or to debug for more verbose logging:

$ export CAS_PARSER_LOG=debug

ProGuard and R8

Although the SDK uses reflection, it is still usable with ProGuard and R8 because cas-parser-java-core is published with a configuration file containing keep rules.

ProGuard and R8 should automatically detect and use the published rules, but you can also manually copy the keep rules if necessary.

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 CasParserOkHttpClient or CasParserOkHttpClientAsync.

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 between requests.

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 request.

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

import com.cas_parser.api.client.CasParserClient;
import com.cas_parser.api.client.okhttp.CasParserOkHttpClient;

CasParserClient client = CasParserOkHttpClient.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 com.cas_parser.api.models.casparser.UnifiedResponse;

UnifiedResponse unifiedResponse = client.casParser().smartParse(RequestOptions.builder().timeout(Duration.ofSeconds(30)).build());

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

import com.cas_parser.api.client.CasParserClient;
import com.cas_parser.api.client.okhttp.CasParserOkHttpClient;
import java.time.Duration;

CasParserClient client = CasParserOkHttpClient.builder()
    .fromEnv()
    .timeout(Duration.ofSeconds(30))
    .build();

Proxies

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

import com.cas_parser.api.client.CasParserClient;
import com.cas_parser.api.client.okhttp.CasParserOkHttpClient;
import java.net.InetSocketAddress;
import java.net.Proxy;

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

HTTPS

Note

Most applications should not call these methods, and instead use the system defaults. The defaults include special optimizations that can be lost if the implementations are modified.

To configure how HTTPS connections are secured, configure the client using the sslSocketFactory, trustManager, and hostnameVerifier methods:

import com.cas_parser.api.client.CasParserClient;
import com.cas_parser.api.client.okhttp.CasParserOkHttpClient;

CasParserClient client = CasParserOkHttpClient.builder()
    .fromEnv()
    // If `sslSocketFactory` is set, then `trustManager` must be set, and vice versa.
    .sslSocketFactory(yourSSLSocketFactory)
    .trustManager(yourTrustManager)
    .hostnameVerifier(yourHostnameVerifier)
    .build();

Custom HTTP client

The SDK consists of three artifacts:

cas-parser-java-core
- Contains core SDK logic
- Does not depend on OkHttp
- Exposes CasParserClient, CasParserClientAsync, CasParserClientImpl, and CasParserClientAsyncImpl, all of which can work with any HTTP client
cas-parser-java-client-okhttp
- Depends on OkHttp
- Exposes CasParserOkHttpClient and CasParserOkHttpClientAsync, which provide a way to construct CasParserClientImpl and CasParserClientAsyncImpl, respectively, using OkHttp
cas-parser-java
- Depends on and exposes the APIs of both cas-parser-java-core and cas-parser-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 cas-parser-java dependency with cas-parser-java-core
Copy cas-parser-java-client-okhttp's OkHttpClient class into your code and customize it
Construct CasParserClientImpl or CasParserClientAsyncImpl, similarly to CasParserOkHttpClient or CasParserOkHttpClientAsync, using your customized client

Completely custom HTTP client

To use a completely custom HTTP client:

Replace your cas-parser-java dependency with cas-parser-java-core
Write a class that implements the HttpClient interface
Construct CasParserClientImpl or CasParserClientAsyncImpl, similarly to CasParserOkHttpClient or CasParserOkHttpClientAsync, 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.cas_parser.api.core.JsonValue;
import com.cas_parser.api.models.casparser.CasParserSmartParseParams;

CasParserSmartParseParams params = CasParserSmartParseParams.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.cas_parser.api.core.JsonValue;
import com.cas_parser.api.models.casparser.CasParserSmartParseParams;

CasParserSmartParseParams params = CasParserSmartParseParams.builder()
    .password(JsonValue.from(42))
    .pdfUrl("https://your-cas-pdf-url-here.com")
    .build();

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

import com.cas_parser.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.cas_parser.api.core.JsonMissing;
import com.cas_parser.api.models.casgenerator.CasGeneratorGenerateCasParams;
import com.cas_parser.api.models.casparser.CasParserSmartParseParams;

CasParserSmartParseParams params = CasGeneratorGenerateCasParams.builder()
    .fromDate("2023-01-01")
    .password("Abcdefghi12$")
    .toDate("2023-12-31")
    .email(JsonMissing.of())
    .build();

Response properties

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

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

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

JsonField<String> password = client.casParser().smartParse(params)._password();

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

  // Try to deserialize into a custom type
  MyClass myObject = password.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 CasParserInvalidDataException 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.cas_parser.api.models.casparser.UnifiedResponse;

UnifiedResponse unifiedResponse = client.casParser().smartParse(params).validate();

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

import com.cas_parser.api.models.casparser.UnifiedResponse;

UnifiedResponse unifiedResponse = client.casParser().smartParse(RequestOptions.builder().responseValidation(true).build());

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

import com.cas_parser.api.client.CasParserClient;
import com.cas_parser.api.client.okhttp.CasParserOkHttpClient;

CasParserClient client = CasParserOkHttpClient.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:

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 6 Commits
.devcontainer		.devcontainer
.github/workflows		.github/workflows
bin		bin
buildSrc		buildSrc
cas-parser-java-client-okhttp		cas-parser-java-client-okhttp
cas-parser-java-core		cas-parser-java-core
cas-parser-java-example		cas-parser-java-example
cas-parser-java-lib		cas-parser-java-lib
cas-parser-java-proguard-test		cas-parser-java-proguard-test
cas-parser-java		cas-parser-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
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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CASParser/cas-parser-java

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Cas Parser Java API Library

Installation

Gradle

Maven

Requirements

Usage

Client configuration

Modifying configuration

Requests and responses

Immutability

Asynchronous execution

Raw responses

Error handling

Logging

ProGuard and R8

Jackson

Network options

Retries

Timeouts

Proxies

HTTPS

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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