如何使用 MultiValueMap 为参数创建 URI/URL？

Question

I have multimap of parameters, like this:

{
    keyA: ["2+4", "4+8"],
    keyB: ["Some words with special chars #ąęć"]
}

as spring MultiValueMap and I'm trying to create URI from this, I tried to use

URI uri = UriComponentsBuilder
           .fromUriString(baseUri).path(somePath)
           .queryParams(params.getQueryParameters())
           .build().encode().toUri();

It seems to work for special chars, but it still does think that + sign is a space, I want to encode all parameters, is there existing solution for this other than manually encoding each value?

Answer 1

Assuming you are on Spring 5.0, this is discussed in detail in [SPR-16860] Spring is inconsistent in the encoding/decoding of URLs issue. More or less it boils down to this:

From an RFC 3986 perspecitve, "+" is a legal character. By default the RestTemplate leaves it as is.

UriComponents.encode() will leave + sign as is, to stay complaint with the RFC 3986. If you need it encoded one suggestion is to use UriUtils :

String value = "A+B=C";
value = UriUtils.encode(value, StandardCharsets.UTF_8); // A%2BB%3DC
URI uri = UriComponentsBuilder.newInstance()
       .queryParam("test", value)
       .build(true)
       .toUri();

There is a change coming 5.0.8 as part of [SPR-17039] Support stricter encoding of URI variables in UriComponents which introduces new UriComponentsBuilder.encode() method. It should be enough to move encode() before build() in your example:

URI uri = UriComponentsBuilder
       .fromUriString(baseUri).path(somePath)
       .queryParams(params.getQueryParameters())
       .encode()
       .build()
       .toUri();