How can I append a query parameter to an existing URL?

Question

I'd like to append key-value pair as a query parameter to an existing URL. While I could do this by checking for the existence of whether the URL has a query part or a fragment part and doing the append by jumping though a bunch of if-clauses but I was wondering if there was clean way if doing this through the Apache Commons libraries or something equivalent.

http://example.com would be http://example.com?name=John

http://example.com#fragment would be http://example.com?name=John#fragment

http://[email protected] would be http://[email protected]&name=John

http://[email protected]#fragment would be http://[email protected]&name=John#fragment

I've run this scenario many times before and I'd like to do this without breaking the URL in any way.

Answer 1

There are plenty of libraries that can help you with URI building (don't reinvent the wheel). Here are three to get you started:

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Java EE 7

import javax.ws.rs.core.UriBuilder; ... return UriBuilder.fromUri(url).queryParam(key, value).build(); 

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org.apache.httpcomponents:httpclient:4.5.2

import org.apache.http.client.utils.URIBuilder; ... return new URIBuilder(url).addParameter(key, value).build(); 

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org.springframework:spring-web:4.2.5.RELEASE

import org.springframework.web.util.UriComponentsBuilder; ... return UriComponentsBuilder.fromUriString(url).queryParam(key, value).build().toUri(); 

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See also: GIST > URI Builder Tests