How to Redirect to an External URL from a Spring MVC Controller Action?

Redirect to an External URL from Controller Action in Spring MVC

When attempting to redirect to an external URL from a controller action in Spring MVC, it's important to understand the limitations of the default "redirect:" syntax. By default, Spring redirects to URLs within the application's context path.

Redirecting to Internal URLs

As demonstrated in the first code snippet:

@RequestMapping(method = RequestMethod.POST)
public String processForm(...) {
    String redirectUrl = "yahoo.com";
    return "redirect:" + redirectUrl;
}

This code attempts to redirect to the URL "yahoo.com" but lacks a valid protocol (e.g., http:// or https://). As a result, Spring interprets it as an internal URL and redirects to "yahoo.com" within the application's context path.

Redirecting to External URLs with Protocol

To redirect to an external URL with a protocol, the following approach can be used:

@RequestMapping(method = RequestMethod.POST)
public String processForm(...) {
    String redirectUrl = "http://www.yahoo.com";
    return "redirect:" + redirectUrl;
}

By specifying the protocol in the URL, Spring correctly redirects the user to the external website.

Redirecting to External URLs Without Protocol

To redirect to an external URL without a protocol using Spring MVC, two alternatives exist:

Method 1:

@RequestMapping(value = "/redirect", method = RequestMethod.GET)
public void method(HttpServletResponse httpServletResponse) {
    httpServletResponse.setHeader("Location", projectUrl);
    httpServletResponse.setStatus(302);
}

This method manually sets the "Location" header and the appropriate HTTP status code (302) in the response to trigger a redirect.

Method 2:

@RequestMapping(value = "/redirect", method = RequestMethod.GET)
public ModelAndView method() {
    return new ModelAndView("redirect:" + projectUrl);
}

This method uses the "ModelAndView" class to create a redirect response with the specified URL.

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