When i try to open swagger on a spring project, show a message Whitelabel Error Page. What is the problem?

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04-10-2024

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"Whitelabel Error Page" in Swagger: A Spring Boot Troubleshooting Guide

Have you ever encountered the frustrating "Whitelabel Error Page" when trying to access your Swagger documentation in a Spring Boot application? It can be incredibly frustrating to see this error instead of the interactive API documentation you expect. This article will guide you through the common causes of this error and equip you with the solutions to get your Swagger UI back up and running.

The Scenario

Imagine you've diligently built your Spring Boot application, meticulously annotated your controllers with Swagger annotations, and eagerly anticipate exploring your API documentation. But, upon accessing the Swagger UI URL (usually /swagger-ui/index.html), you're met with the dreaded "Whitelabel Error Page". This error can be caused by a variety of issues, from missing dependencies to configuration mishaps.

Examining the Code

Let's assume you're using Springfox, a popular Swagger implementation for Spring Boot. Your pom.xml might look something like this:

<dependency>
  <groupId>io.springfox</groupId>
  <artifactId>springfox-swagger2</artifactId>
  <version>3.0.0</version>
</dependency>
<dependency>
  <groupId>io.springfox</groupId>
  <artifactId>springfox-swagger-ui</artifactId>
  <version>3.0.0</version>
</dependency>

Additionally, your @SpringBootApplication class might have a @EnableSwagger2 annotation for enabling Swagger.

Unveiling the Culprit

Here are some of the most common reasons behind the "Whitelabel Error Page" in your Swagger UI:

1. Missing Dependencies:

• Double-check that you have included both springfox-swagger2 and springfox-swagger-ui dependencies in your pom.xml. Ensure they are the correct versions compatible with your Spring Boot version.
• Some additional dependencies might be required depending on your project configuration, such as springfox-bean-validators for validating your API models.

2. Spring Security Interference:

• If you're using Spring Security, it might be blocking access to Swagger's resources.
• You can create a configuration class to allow access to "/swagger-ui/**" and "/v2/api-docs" paths. Here's an example:

@Configuration
@EnableWebSecurity
public class WebSecurityConfig extends WebSecurityConfigurerAdapter {

    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http
                .authorizeRequests()
                .antMatchers("/swagger-ui/**", "/v2/api-docs").permitAll()
                .anyRequest().authenticated()
                .and()
                .httpBasic();
    }
}

3. Configuration Errors:

• Review your Swagger configuration carefully. Ensure that your @EnableSwagger2 annotation is present, and that any custom configuration classes are correctly wired in your Spring Boot application.
• Check for any typos in your Swagger configuration or errors in your API documentation annotations.

4. Server Issues:

• Restart your application server to ensure that all changes are properly reflected.
• If you're running the application in a development environment, verify that your application is running on the correct port and is accessible.

Addressing the Problem

1. Dependency Check: Begin by verifying that you have the necessary Swagger dependencies in your pom.xml. If not, include them and re-build your project.

2. Security Configuration: If you're using Spring Security, make sure your configuration allows access to Swagger resources.

3. Configuration Review: Examine your Swagger configuration thoroughly for any typos or inconsistencies.

4. Restart: Restart your Spring Boot application to ensure the changes take effect.

5. Environment Verification: If you're running in a development environment, make sure your application is running on the correct port and is accessible.

Conclusion

The "Whitelabel Error Page" is a common issue when setting up Swagger in a Spring Boot application. By carefully reviewing the dependencies, security configuration, and Swagger configuration, you can swiftly identify and resolve the problem. Remember to double-check for common mistakes like typos, version mismatches, and potential Spring Security conflicts. With these steps, you can regain control of your Swagger UI and confidently explore your API documentation.