JwtIssuerReactiveAuthenticationManagerResolver eagerly creates Exceptions

[robotmrv]

Summary

JwtIssuerReactiveAuthenticationManagerResolver eagerly creates Exceptions which are not thrown always
see

spring-security/oauth2/oauth2-resource-server/src/main/java/org/springframework/security/oauth2/server/resource/authentication/JwtIssuerReactiveAuthenticationManagerResolver.java

Lines 122 to 125 in a90e579

	.flatMap(issuer ->
	this.issuerAuthenticationManagerResolver.resolve(issuer).switchIfEmpty(
	Mono.error(new InvalidBearerTokenException("Invalid issuer " + issuer)))
	);

and

spring-security/oauth2/oauth2-resource-server/src/main/java/org/springframework/security/oauth2/server/resource/authentication/JwtIssuerReactiveAuthenticationManagerResolver.java

Lines 143 to 146 in a90e579

	String issuer = JWTParser.parse(token.getToken()).getJWTClaimsSet().getIssuer();
	return Mono.justOrEmpty(issuer).switchIfEmpty(
	Mono.error(new InvalidBearerTokenException("Missing issuer")));
	} catch (Exception e) {

Actual Behavior

Exceptions are instantiated always

Expected Behavior

Exceptions should be instantiated lazily only when they are needed

Version

5.3.0.BUILD-SNAPSHOT