How do you configure CORS globally in a Spring Boot application?

Table of Contents

Introduction

In a Spring Boot application, you might need to configure CORS (Cross-Origin Resource Sharing) globally to allow or restrict cross-origin requests from external domains. By default, Spring Boot does not allow cross-origin requests for security reasons. CORS must be explicitly configured to enable requests from different origins, such as a frontend application hosted on a different domain or port.

This guide explains how to configure CORS globally in a Spring Boot application using various methods, including the WebMvcConfigurer interface, CorsFilter, and Spring Security for more advanced cases.

Methods to Configure CORS Globally in Spring Boot

1. Using **WebMvcConfigurer** to Configure CORS Globally

The most common way to configure CORS globally in Spring Boot is by implementing the WebMvcConfigurer interface. This allows you to customize the default Spring MVC configuration, including CORS settings.

Example of Global CORS Configuration Using WebMvcConfigurer:

Key Points:

  • **addMapping("/**")**: Applies the CORS settings to all endpoints in the application.
  • **allowedOrigins()**: Specifies which origins are allowed to make requests. You can set multiple origins or "*" to allow any origin (not recommended for production).
  • **allowedMethods()**: Defines which HTTP methods are permitted (e.g., GET, POST, etc.).
  • **allowedHeaders("*")**: Specifies which headers can be used in the request. "*" means all headers are allowed.
  • **allowCredentials(true)**: If set to true, credentials (such as cookies or HTTP authentication) will be allowed.
  • **maxAge()**: Sets the maximum time (in seconds) for which the browser should cache the preflight response. A value of 3600 seconds means the cache will last for one hour.

Use Case Example:

  • If your frontend is hosted on http://localhost:3000, you would configure Spring Boot to allow only that origin to make requests to your backend API, while allowing GET, POST, and DELETE methods.

2. Using **CorsFilter** for Global CORS Configuration

If you need more control or wish to create a more flexible configuration, you can use the CorsFilter bean in your Spring Boot application. This method is often used when you need to apply CORS settings across multiple URL patterns or implement complex CORS policies.

Example of Configuring CORS Using CorsFilter:

Explanation:

  • The CorsConfiguration object is configured with the same properties as in the WebMvcConfigurer example but gives you more flexibility to add more complex rules.
  • The CorsFilter is then registered globally using the UrlBasedCorsConfigurationSource object.

3. Configuring CORS in Spring Security

When you use Spring Security, CORS must be configured explicitly within the security configuration. This is important because Spring Security has its own mechanisms for handling cross-origin requests, and by default, it will block them.

Example of Configuring CORS in Spring Security:

Explanation:

  • **http.cors().and()**: This enables CORS support in Spring Security by integrating it with the global CORS configuration (e.g., CorsFilter or WebMvcConfigurer).
  • **antMatchers("/**").permitAll()**: This line allows unrestricted access to all endpoints. You can adjust this based on your security requirements.

4. Using **@CrossOrigin** for Specific Endpoints

While this method doesn't configure CORS globally, it's worth mentioning that Spring provides the @CrossOrigin annotation to configure CORS at the method or controller level. This can be useful when you want to apply CORS to only specific APIs or controllers.

Example of Method-Level CORS Configuration:

Explanation:

  • **@CrossOrigin(origins = "http://localhost:3000")**: This applies CORS only to the specific method, allowing the frontend from http://localhost:3000 to access the /api/data endpoint.

Conclusion

Configuring CORS globally in a Spring Boot application ensures that your application can accept cross-origin requests from trusted domains while maintaining security. Here’s a quick recap of the methods you can use to configure CORS globally in Spring Boot:

  1. **WebMvcConfigurer**: A straightforward and flexible approach to configuring CORS globally for all endpoints.
  2. **CorsFilter**: Offers more control over the CORS configuration, especially for complex scenarios.
  3. Spring Security: If using Spring Security, you must enable CORS support explicitly within the security configuration.
  4. **@CrossOrigin**: Apply CORS configuration on a method or controller basis for specific routes.

Each method can be used depending on your application’s requirements. For most use cases, configuring CORS globally using WebMvcConfigurer or CorsFilter will suffice, ensuring that cross-origin requests are handled efficiently and securely.

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