Swagger 3 getting Whitelabel Error Page in SpringBoot 3

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05-10-2024

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Swagger 3 Whitelabel Error Page in Spring Boot 3: A Common Issue and its Solutions

Problem: When integrating Swagger 3 into your Spring Boot 3 application, you might encounter a whitelabel error page instead of the expected Swagger UI. This can be frustrating, especially when you're eager to test your APIs.

Rephrasing: Imagine you've set up Swagger to document your Spring Boot application's APIs. When you try to access the Swagger UI, you're met with a plain, unhelpful "Whitelabel Error Page." This means something's wrong with how your application is handling the Swagger UI resources.

Scenario & Code:

Let's assume you've included the following dependencies in your pom.xml:

<dependency>
    <groupId>org.springdoc</groupId>
    <artifactId>springdoc-openapi-ui</artifactId>
    <version>1.7.0</version>
</dependency>

And you have a simple Spring Boot application with a @RestController annotated controller.

Analysis & Clarification:

The root cause usually lies in Spring Boot's error handling mechanisms. By default, Spring Boot 3 uses a BasicErrorController which displays a generic error page. In our case, this controller intercepts requests for the Swagger UI resources, leading to the whitelabel error page.

Solutions:

1. Customize Error Handling:

   • Create a Custom ErrorController: Override the default BasicErrorController to handle errors specific to Swagger. You can customize the error message or redirect to a custom error page.

   • Override Error Handling: In your Application class, add the following code to override the default error handling:

     @SpringBootApplication
     public class Application {
     
         public static void main(String[] args) {
             SpringApplication.run(Application.class, args);
         }
     
         @Bean
         public ErrorPageRegistry errorPageRegistry() {
             ErrorPageRegistry registry = new ErrorPageRegistry();
             registry.addErrorPages(new ErrorPage(HttpStatus.NOT_FOUND, "/swagger-ui.html"));
             return registry;
         }
     }
     

2. Use the springdoc-openapi-ui Dependency:

   • Ensure Correct Configuration: Double-check that you're using the right dependency (springdoc-openapi-ui) and that it's correctly configured in your pom.xml. This dependency includes necessary components to serve the Swagger UI.

3. Check for Conflicts:

   • Verify Dependencies: Make sure you're not using other libraries that might interfere with Swagger's default setup. Review your dependencies and resolve any conflicts.

Additional Value:

• Debugging Tips: Enable debugging in your application to get more detailed error logs. This can help you identify the specific issue causing the error.
• Spring Boot Documentation: Refer to the official Spring Boot documentation for detailed information on error handling and customization: https://docs.spring.io/spring-boot/docs/current/reference/html/spring-boot-features.html#boot-features-error-handling
• Swagger UI Documentation: Consult the Swagger UI documentation for instructions on configuring and customizing the UI: https://swagger.io/docs/open-source-tools/swagger-ui/

Conclusion:

By understanding the common causes of the Swagger 3 whitelabel error page and implementing the solutions provided, you can quickly troubleshoot and resolve this issue. Remember to analyze your specific setup, debug your application, and leverage available resources for a smoother development experience.