Why Doesn't Java's HttpURLConnection Follow Redirects Between HTTP and HTTPS?

HTTPURLConnection Redirects: Protocol Restrictions

Java's HttpURLConnection provides a convenient way to send HTTP requests, but when dealing with redirects, it adheres to certain rules. One such rule is that redirects are followed only if the destination URL uses the same protocol as the original request.

In the given example, the original URL is an HTTP URL ("http://httpstat.us/301") and the redirect URL is an HTTPS URL ("https://httpstat.us"). The HttpURLConnection does not follow this redirect because HTTPS is considered a different protocol from HTTP. This behavior is hardcoded in the followRedirect() method, providing no way to disable this check.

This protocol restriction stems from security concerns. While HTTPS is often considered a secure alternative to HTTP, from an HTTP protocol perspective, HTTPS is treated as a separate and unfamiliar protocol. Allowing unverified redirects to HTTPS would introduce potential risks. For instance, if automatic client authentication is configured and the initial request is HTTP-based, the client's identity could be inadvertently revealed to the server if the redirect to HTTPS is blindly followed.

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