REST API Testing with Postman & Swagger

When developing RESTful APIs in Java, especially with frameworks like Spring Boot, it’s essential to ensure that your APIs work as expected. Two powerful tools for this are Postman and Swagger.

Postman

Postman is an intuitive tool that allows you to test REST APIs quickly and effectively. It helps in sending requests to your API and examining the responses.

• Create a Request: Set up the HTTP method (GET, POST, PUT, DELETE) and specify the URL for your API endpoint.
• Set Request Headers: For APIs that require authentication or specific content types, you can set headers like Authorization, Content-Type, and more.
• Send the Request: Once your request is ready, click “Send.” Postman will provide the status code, response body, headers, and more.
• Assertions: Postman allows you to write tests in JavaScript to validate API responses. For example, you can check if the response status code is 200 or if the returned JSON matches expected data.

Example Test Script in Postman

Swagger

Swagger (now part of the OpenAPI specification) is widely used for documenting REST APIs. It not only generates API docs but also provides interactive testing of your API endpoints.

Integrating Swagger in Spring Boot

• Add Swagger Dependency: In your pom.xml, add the dependency for Swagger UI.
  
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  <dependency>     <groupId>io.springfox</groupId>     <artifactId>springfox-boot-starter</artifactId>     <version>3.0.0</version> </dependency>

• Configure Swagger: In your Spring Boot application, configure Swagger to scan your API controllers.
  
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  @Configuration @EnableOpenApi public class SwaggerConfig {     @Bean     public OpenAPI customOpenAPI() {         return new OpenAPI()             .info(new Info().title("My API").version("1.0"));     } }

• Access Swagger UI: After running your Spring Boot application, navigate to http://localhost:8080/swagger-ui/ to view and test your API directly through the browser.

Advantages of Swagger for Testing

• Interactive Docs: Swagger generates an interactive interface where you can test the API methods by sending real requests and viewing responses.
• Easy Integration: With Spring Boot, Swagger integrates seamlessly and generates user-friendly documentation.
• Self-Updated Docs: As you modify your API, Swagger docs stay updated, providing a live reference.