Exploring IntelliJ IDEA’s Built-In REST Client for API Testing

Introduction
If you’re a Java developer, you’re likely familiar with IntelliJ IDEA — the highly popular Integrated Development Environment (IDE) built by JetBrains. IntelliJ IDEA provides an extensive suite of tools that are designed to improve productivity, streamline development, and ultimately help us craft high-quality code.
But, did you know that IntelliJ IDEA also offers a built-in REST client for API testing? This built-in functionality has become a compelling alternative to standalone API testing tools like Postman or Insomnia. This blog post will explore this less-known, yet powerful, feature of IntelliJ IDEA and how you can use it to simplify your API testing process.
Getting Started with IntelliJ’s Built-in REST Client
To access the HTTP Client in IntelliJ IDEA, you need to create an HTTP request file. To do this, right-click on your project in the Project Tool Window, navigate to ‘New’, and then select ‘HTTP Request’. This creates a new file with an .http
extension where you can write and execute HTTP requests.
### This is a simple GET request
GET https://api.github.com/users/octocat
Accept: application/json
When you’re ready to send the request, click on the green play button to the left of the request. IntelliJ will execute the request and display the response in the ‘Run’ tab at the bottom of the IDE.
Powerful Features of the Built-in REST Client
IntelliJ IDEA’s HTTP client packs a lot of powerful features that enhance API testing capabilities.
- Environment Variables: IntelliJ’s HTTP client supports environment variables. You can define and manage these variables in different environments using the
Environments
option.
# This is a POST request with environment variables
POST {{host}}/api/users
Content-Type: application/json
{
"name": "John Doe",
"email": "[email protected]"
}
In the above code, {{host}}
is an environment variable that you can define for different environments (like Production, Staging, etc.).
- Language Injection: IntelliJ supports language injection. For example, if your response is a JSON, you can inject the JSON language, which allows for easier reading and navigation.
- Code Auto-completion and Navigation: The HTTP client in IntelliJ IDEA supports auto-completion of method types (GET, POST, etc.), header fields (Content-Type, Accept, etc.), and even file paths. The tool also supports navigating to referenced files by using
Ctrl+Click
on the file path.
### Send a file as the request body
POST http://example.com/api/upload
Content-Type: multipart/form-data
{
"file": "< ./path/to/your/file.txt"
}
- Scripting and Chaining Requests: IntelliJ IDEA’s HTTP client supports JavaScript for preprocessing requests and postprocessing responses. This allows you to chain HTTP requests and make your API testing more dynamic and flexible.
# Preprocess a request using JavaScript
POST http://example.com/api/auth
Content-Type: application/json
X-Request-Id: {{randomUUID()}}
# Use the response from a previous request in a new one
GET http://example.com/api/profile
Content-Type: application/json
Authorization: Bearer {{accessToken()}}
Conclusion
IntelliJ IDEA’s built-in HTTP client is a powerful tool for API testing. With features like environment variables, language injection, code auto-completion, and request chaining, this tool can streamline your API testing process and help you write more effective tests. So, the next time you’re testing an API, consider leveraging IntelliJ IDEA’s built-in HTTP client.
Keep in mind that while this tool has many robust features, it might not fully replace standalone API testing tools, especially for more complex testing scenarios. However, for simple to moderately complex use-cases, it certainly comes in handy and reduces the need to switch between your IDE and API testing tool.