Add queryParam method to MockHttpServletRequestBuilder

[OrangeDog]

ServletUriComponentsBuilder uses HttpServletRequest#getQueryString to build on the current request.
However, in a GET or HEAD request, MockHttpServletRequestBuilder#param only adds to the combined parameter map and not the query string, causing it to fail.

The workaround is to provide the parameters directly in the URI string, but this is inferior to the fluent API. The different behaviour is probably surprising to many users.

See also spring-projects/spring-restdocs#26

[rstoyanchev]

You can supply a URL with a query to MockMvcRequestBuilders. The query is parsed and appended to the params map. I suppose we could allow it in the reverse order too, if the request is GET or HEAD and there is no body, but isn't the first option a more self-explanatory way to do it?

[OrangeDog]

@rstoyanchev I know, that's why I mentioned it.

The workaround is to provide the parameters directly in the URI string, but this is inferior to the fluent API. The different behaviour is probably surprising to many users.

Every other part of the the request has a structured way to set it except the querystring, which requires manual encoding and concatenation.

An alternative is to add queryParam or query methods as well as param. I'm not sure whether that would be more confusing, though it better supports the case of POST requests with both a querystring and a body.

[rstoyanchev]

Apologies I missed that part of your comment.

I don't see providing the query in the URI template as a workaround. It is the primary way of specifying the target URI with all of its components including the query. The URI template by the way is encoded so I do not see a need for manual encoding. And you can also use UriComponentsBuilder to prepare the URI and pass that in.

That said we can add a queryParam method as an extra convenience, and that will append to query of the target URI.

[rstoyanchev]

This is now superseded by #23980.