Java - Replace host in url?

Question

In java, I'd like to replace the Host part of an url with a new Host, where both the host and url are supplied as a string.

This should take into account the fact that the host could have a port in it, as defined in the RFC

So for example, given the following inputs

• url: http://localhost/me/out?it=5
• host: myserver:20000

I should get the following output from a function that did this correctly

• http://myserver:20000/me/out?it=5

Does anyone know of any libraries or routines that do Host replacement in an url correctly?

EDIT: For my use case, I want my host replacement to match what a java servlet would respond with. I tried this out by running a local java web server, and then tested it using curl -H 'Host:superduper.com:80' 'http://localhost:8000/testurl' and having that endpoint simply return the url from request.getRequestURL().toString(), where request is a HttpServletRequest. It returned http://superduper.com/testurl, so it removed the default port for http, so that's what I'm striving for as well.

Answer 1

The Spring Framework provides the UriComponentsBuilder. You can use it like this:

import org.springframework.web.util.UriComponentsBuilder;

String initialUri = "http://localhost/me/out?it=5";
UriComponentsBuilder builder = UriComponentsBuilder.fromHttpUrl(initialUri);
String modifiedUri = builder.host("myserver").port("20000").toUriString();
System.out.println(modifiedUri);
// ==> http://myserver:20000/me/out?it=5

Here you need to provide hostname and port in separate calls to get right encoding.