@azure/core-client

What is @azure/core-client?

The @azure/core-client package is designed to be a foundational library for all Azure SDK client libraries. It provides the core functionalities such as HTTP pipeline, serialization, and deserialization of responses, handling of authentication protocols, and error handling. It is intended to streamline the development of Azure SDKs by providing common functionalities needed for interacting with Azure services.

What are @azure/core-client's main functionalities?

HTTP Pipeline

This feature allows developers to customize the HTTP pipeline used for sending requests to Azure services. It includes adding custom policies, using a default HTTP client, and configuring the pipeline with various options.

const { PipelinePolicy, createDefaultHttpClient, createPipelineFromOptions } = require('@azure/core-client');

const httpClient = createDefaultHttpClient();
const pipeline = createPipelineFromOptions({});
pipeline.addPolicy(somePolicy);
const client = new SomeServiceClient(url, credential, { httpClient, pipeline });

Authentication

This feature demonstrates how to use the @azure/identity package with @azure/core-client to authenticate requests to Azure services. It simplifies the process of using Azure Active Directory tokens for authentication.

const { TokenCredential, DefaultAzureCredential } = require('@azure/identity');
const { SomeServiceClient } = require('@azure/some-service');

const credential = new DefaultAzureCredential();
const client = new SomeServiceClient('<your-service-endpoint>', credential);

Serialization and Deserialization

This feature is about serializing request payloads before sending them to Azure services and deserializing responses. It ensures that data is correctly formatted for network transmission and subsequent processing.

const { serialize, deserialize } = require('@azure/core-client');

const model = { name: 'Azure SDK' };
const serializedModel = serialize(model);
const deserializedModel = deserialize(serializedModel);

Other packages similar to @azure/core-client

axios

Axios is a popular HTTP client for the browser and node.js. While it provides features for making HTTP requests and handling responses, it lacks the Azure-specific integrations and authentication protocols that @azure/core-client offers.

node-fetch

node-fetch is a lightweight module that brings window.fetch to Node.js. Similar to axios, it allows for making HTTP requests but does not include the Azure-specific features or the extensive HTTP pipeline customization options available in @azure/core-client.

request

Request is a simplified HTTP request client for Node.js, but it has been deprecated. While it was widely used for making HTTP requests, it does not offer the Azure service integrations or the authentication and pipeline customization capabilities of @azure/core-client.

README

Azure Core Service client library for JavaScript

This library is primarily intended to be used in code generated by AutoRest and autorest.typescript.

Getting started

Currently supported environments

• LTS versions of Node.js
• Latest versions of Safari, Chrome, Edge, and Firefox.

See our support policy for more details.

Installation

This package is primarily used in generated code and not meant to be consumed directly by end users.

Key concepts

ServiceClient

This is the common base class for generated clients. It provides the methods sendOperationRequest and sendRequest.

sendRequest simply makes an HTTP request using a Pipeline (see @azure/core-rest-pipeline for details.)

sendOperationRequest is used by generated code to make a request using an OperationSpec and OperationArguments. An OperationSpec is a translation of request requirements from the OpenAPI/Swagger file that describes the service.

createClientPipeline

This method is used to create a Pipeline instance that is customized with extra policies that perform serialization and deserialization. The bulk of the work is in converting requests into the right HTTP message that a service expects and then converting the HTTP response payload into the response shape described by the service's OpenAPI specification file.

Mappers / createSerializer

Mappers are used to encode and decode data into HTTP headers and bodies. They describe all request and response fields. They are referenced by OperationSpecs.

The method createSerializer creates a Serializer that is used to do the bulk of the work transforming data when making a request or processing a response. Given a corpus of Mappers and the appropriate OperationSpec it can manufacture an HTTP request object from a user provided input or convert an HTTP response object into a user-friendly form.

Next steps

You can build and run the tests locally by executing rushx test. Explore the test folder to see advanced usage and behavior of the public classes.

Learn more about AutoRest and the autorest.typescript extension for generating a compatible client on top of this package.

Troubleshooting

If you run into issues while using this library, please feel free to file an issue.

Contributing

If you'd like to contribute to this library, please read the contributing guide to learn more about how to build and test the code.