Spring MVC's "redirect:" Prefix: Your Go-To for External HTTP Journeys

 

Spring MVC's redirect: prefix is a powerful and concise way to perform an HTTP redirect from your controller method. When you return a String starting with redirect:, Spring understands you want the browser to issue a new request to the specified URL.

A common and important use case for this is redirecting to external URLs, including those with http:// or https:// protocols. Unlike internal forwards, which remain within your application's DispatcherServlet and retain the original request attributes, a redirect: sends an HTTP 302 (Found) status code back to the client, along with a Location header containing the new URL. The client then initiates a completely fresh request to that location.

 

@Controller
public class MyController {

    @GetMapping("/external-link")
    public String redirectToExternalSite() {
        // This will redirect the user's browser to Google's homepage
        return "redirect:http://www.google.com";
    }

    @GetMapping("/secure-redirect")
    public String redirectToSecureExternalSite() {
        // Redirect to an HTTPS site
        return "redirect:https://www.secure-app.com/login";
    }
}

This flexibility makes redirect: invaluable for scenarios like:

• OAuth/SSO callbacks: Redirecting users to an identity provider's login page and back.
• Payment gateways: Sending users to external payment processing sites.
• Linking to external resources: Directing users to documentation, partner sites, or other web applications.

Key takeaway: When you need the client's browser to make a fresh request to an entirely different URL, even one on a different domain or protocol, Spring MVC's redirect: prefix with a full URL (including http:// or https://) is the simple and correct approach.