UriComponentsBuilder does not encode "+" depending on spring version

phenomenon

Suppose you want to encode query parameters with code like the following.

MultiValueMap<String, String> params = new LinkedMultiValueMap<>();
params.add("key", "a+b");
String u = UriComponentsBuilder.fromHttpUrl("http://www.google.com").queryParams(params).build().encode().toString();

System.out.println(u);

The result of the above code depends on the version of spring-web as shown in the table below.

In the new 5.0, the "+" is no longer encoded.

Cause

Implementation of query parameter encoding, as described around https://stackoverflow.com/questions/50432395/whats-the-proper-way-to-escape-url-variables-with-springs-resttemplate-when-ca Has changed to RFC 3986 base, so somehow.

Check the implementation. A class called HierarchicalUriComponents is actually in charge of encoding, and there is a part inside it that determines whether or not it is an encoding target.

This is the case in 4.3.

		QUERY_PARAM {
			@Override
			public boolean isAllowed(int c) {
				if ('=' == c || '+' == c || '&' == c) {
					return false;
				}
				else {
					return isPchar(c) || '/' == c || '?' == c;
				}
			}
		},

In 5.0, this is the case, and you can see that the "+" is off.

		QUERY_PARAM {
			@Override
			public boolean isAllowed(int c) {
				if ('=' == c || '&' == c) {
					return false;
				}
				else {
					return isPchar(c) || '/' == c || '?' == c;
				}
			}
		},