Mastering Postman: A Step‑by‑Step Guide for API Testing with Spring Boot

Installing Postman

Postman is distributed as a standalone application for Windows, macOS and Linux. Download the installer from the official site https://www.getpostman.com/downloads/ and run the installer that matches your operating system. The article was written when version 7.14.0 was the latest.

Core capabilities

Postman can send any HTTP method (GET, POST, PUT, DELETE, HEAD, PATCH, etc.) with custom headers, query parameters, and request bodies. It supports authentication schemes such as Basic, Digest and OAuth 1.0/2.0. Responses are displayed with syntax highlighting for JSON, XML, HTML or plain text. Requests can be saved in collections and request history is recorded automatically.

Example: Mock login API with Spring Boot

Create a minimal Spring Boot project that exposes a /login endpoint returning a JSON object. The controller implementation is:

@RestController
public class PostmanController {

    @PostMapping("login")
    public Result login(String username, String password){
        Result result = new Result();
        result.setCode(0);
        result.setDesc("success");
        return result;
    }
}

Creating the request in Postman

In Postman click New → Request , give the request a name, select a collection to store it, and set the request URL to the running Spring Boot server (e.g., http://localhost:8080/login). Choose the HTTP method POST. Parameters can be added in three ways:

Params tab – adds query‑string parameters to the URL.

Headers tab – adds HTTP header fields.

Body tab – for form‑encoded data or raw JSON payloads. For a JSON body use the raw option and select JSON as the format, then provide {"username":"admin","password":"12345"}.

Click Send to execute the request; the response pane shows the JSON result with syntax highlighting.

Variables and environments

Postman supports placeholders using the {{variable}} syntax. Define a variable (e.g., url) in an environment (gear icon → Manage Environments). Typical environments are dev and prod, each providing a different base URL. The request URL can be written as {{url}}/login and Postman will substitute the appropriate value at runtime.

Generating client code

After a request is configured, click the Code link at the bottom of the request pane. Postman generates ready‑to‑run snippets in languages such as cURL, Java (OkHttp), Python (requests), etc. The generated code can be copied into automated test suites or other applications.

Summary

The steps above demonstrate the essential workflow for API testing with Postman: installing the tool, creating a request against a Spring Boot endpoint, using environment variables for flexible URL management, and exporting request code for reuse. Advanced features such as test scripts, mock servers and CI integration are documented in the official Postman documentation.