How to forward to an external url? - spring

Question

My Spring based app is running under http://localhost. Another app is running under http://localhost:88. I need to achieve the following: when a user opens http://localhost/page, a content of http://localhost:88/content should be shown.
I've supposed, that I should use forwarding, like shown bellow:
#RequestMapping("/page")
public String handleUriPage() {
return "forward:http://localhost:88/content";
}
but seems like forwarding to an external URL doesn't work.
How can I achieve this behaviour with Spring?

Answer 1

Firstly, you specify that you want to show the content of "http://localhost:88/content" but you actually forward to "http://localhost:88" in your method.
Nevertheless, forward works with relative URLs only (served by other controllers of the same application), so you should use 'redirect:' instead.
Forward happens entirely on the server side: the Servlet container forwards the same request to the target URL, so the URL won't change in the address bar.
Redirect, on the other hand, will cause the server to respond with 302 and the Location header set to the new URL, after which the client browser will make a separate request to it, changing the URL in the address bar, of course.
UPDATE: For returning the content of the external page as it would be an internal one, I would write a separate controller method to make the request to the URL and just return its content. Something like the following:
#RequestMapping(value = "/external", produces = MediaType.TEXT_HTML_VALUE)
public void getExternalPage(#RequestParam("url") String url, HttpServletResponse response) throws IOException {
HttpClient client = HttpClients.createDefault();
HttpGet request = new HttpGet(url);
HttpResponse response1 = client.execute(request);
response.setContentType("text/html");
ByteStreams.copy(response1.getEntity().getContent(), response.getOutputStream());
}
Of course, you have many possible solutions. Here I used Apache Commons HttpClient for making the request, and Google's Guava for copying the response from that request to the resulting one.
After that, your return statement would change to the following:
return "forward:/external?url=http%3A%2F%2Flocalhost%3A88%2Fcontent"
Note how you need to encode your URL given as parameter.