Create a HTTP Client with Apache HttpClient

Table Of Contents

In this article series, we’re going to explore Apache HTTPClient APIs. We’ll get familiar with the different ways Apache HttpClient enables developers to send and receive data over the internet. From simple GET requests to complex multipart POST requests, we’ll cover it all with real-world examples.

So get ready to learn web communication with Apache HttpClient!

The “Create an HTTP Client with Apache HttpClient” Series

This article is the first part of a series:

  1. Introduction to Apache HttpClient
  2. Apache HttpClient Configuration
  3. Classic APIs Offered by Apache HttpClient
  4. Async APIs Offered by Apache HttpClient
  5. Reactive APIs Offered by Apache HttpClient

Why Should We Care About HTTP Clients?

Have you ever wondered how your favorite apps seamlessly fetch data from the internet or communicate with servers behind the scenes? That’s where HTTP clients come into play — they’re the silent heroes of web communication, doing the heavy lifting, so you don’t have to.

Imagine you’re using a weather app to check the forecast for the day. Behind the scenes, the app sends an HTTP request to a weather service’s server, asking for the latest weather data. The server processes the request, gathers the relevant information, and sends back an HTTP response with the forecast. All of this happens in the blink of an eye, thanks to the magic of HTTP clients.

HTTP clients are like digital messengers, facilitating communication between client software and web servers across the internet. They handle all the details of making a connection to the server, sending HTTP requests, and processing responses, so you can focus on building great software without getting bogged down in the complexities of web communication.

So why should you care about HTTP clients? Well, imagine if every time you wanted to fetch data from a web server or interact with a web service, you had to manually craft and send HTTP requests, then parse and handle the responses — it would be a nightmare! HTTP clients automate all of that for you, making it easy to send and receive data over the web with just a few lines of code.

When it comes to developing a mobile app, a web service, or anything in between, HTTP clients plays a crucial role in facilitating interaction with remote resources on the internet. Therefore, it is important to acknowledge its significance when building software that requires web communication.

Examples of HTTP Clients

There are many Java HTTP clients available. Check this article on Comparison of Java HTTP Clients for more details.

Brief Overview of the Apache HttpClient

Apache HttpClient is a robust Java library popular for its handling of HTTP requests and responses. Its open-source nature and adherence to modern HTTP standards contribute to its popularity among developers.

Key features include support for various authentication mechanisms and connection pooling, enhancing performance by reusing connections. It also facilitates request and response interception, allowing for easy modification or inspection of data.

Notably, Apache HttpClient is known for its reliability and resilience, making it ideal for critical applications. Its extensive functionality, including support for multiple HTTP methods and advanced handling capabilities, caters to diverse needs in the HTTP ecosystem.

The library’s flexibility and extensibility enable customization to specific requirements, while its supportive community ensures continuous development and maintenance. With a commitment to backward compatibility, they facilitate seamless upgrades, ensuring long-term applicability and ease of use. Overall, Apache HttpClient stands as a mature and reliable choice for Java developers handling HTTP interactions.

Getting Familiar With Useful Terms of the Apache HttpClient

In the domain of Apache HttpClient, a lot of terms are essential for comprehending the functionality of this robust tool. At its core lies the HTTPClient. It comes in two versions — the classic HttpClient and the async HttpAsyncClient. CloseableHttpClient is an abstract class implementing the HttpClient interface. The library provides MinimalHttpClient that extends it. It is a vital component that manages connections to HTTP servers. Think of it as the communication manager, ensuring seamless and secure data exchanges between your application and web resources.

CloseableHttpClient provides full control over resources and ensures proper closure of connections after use. It supports connection pooling and resource management, making it suitable for long-lived applications.

MinimalHttpClient is a minimal implementation of CloseableHttpClient. Apache optimizes this client for HTTP/ 1.1 message transport and does not support advanced HTTP protocol functionality such as request execution via a proxy, state management, authentication, and request redirects.

Now let’s check the async client. HttpAsyncClient is an asynchronous HTTPClient in Apache HttpComponents, designed for non-blocking I/O operations, making it suitable for high-performance, scalable applications with many concurrent requests.

CloseableHttpAsyncClient is an abstract class. It implements HttpAsyncClient, providing a convenient way to manage the life cycle of the asynchronous HTTP client, allowing for graceful shutdown.

MinimalHttpAsyncClient is a minimal implementation of CloseableHttpAsyncClient. Apache optimizes this client for HTTP/ 1.1 and HTTP/ 2 message transport and does not support advanced HTTP protocol functionality such as request execution via a proxy, state management, authentication, and request redirects.

As your application makes interactions with remote resources on the internet, it encounters HttpResponse, a capsule of information that carries the outcome of each interaction. This response conveys the server’s message, whether it signifies success, error, or redirection.

HttpResponse comes with its counterpart, CloseableHttpResponse. It not only conveys the server’s response but also gracefully closes connections after use, preventing resource leaks and enhancing performance. Isn’t that a nice to have feature?

Then we also have Headers, tiny snippets of metadata that accompany every HTTP request and response. These headers contain valuable details like content type, encoding, and authentication tokens, facilitating the exchange of data between client and server.

We put to use HttpHost to encapsulate the server’s hostname and port number, acting as a navigational aid for our HTTP requests.

Implementing web interceptions would be incomplete without encountering HttpEntity, the carrier that transports data across the servers. Whether it’s text, binary, or streaming content, HttpEntity offers a unified interface for managing data payloads effortlessly.

We would come across a variety of HTTP methods, each serving a distinct purpose. From HttpGet for retrieving data to HttpPost for creating new resources, and HttpPut for updating existing ones, these methods empower us to engage with web resources effectively.

In upcoming articles in this series, we’re going to learn how to implement our web interactions using these terms.

Conclusion

Apache HttpClient simplifies HTTP communication in Java applications. With intuitive APIs, it enables developers to perform various HTTP operations, including GET, POST, PUT, and DELETE, and more. Offering flexibility and robustness, it facilitates seamless integration with web services, making it ideal for building web applications, RESTful APIs, and microservices. Whether fetching data from external APIs or interacting with web resources, Apache HttpClient provides a reliable solution for handling HTTP requests and responses efficiently. Its extensive features, along with easy-to-use interfaces, make it a preferred choice for developers seeking a powerful and versatile HTTP client library in their Java projects.

Apache HttpClient offers classic (synchronous or blocking), asynchronous and reactive APIs. In the upcoming articles of this series, we will learn about these APIs.

Written By:

Sachin Raverkar

Written By:

Sachin Raverkar

Sachin is a Java enthusiast with over two decades of product development expertise. He enjoys architecting and delivering SAAS products as well as sharing expertise with people all over the world.

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