core/src/main/java/org/springframework/security/core/authority/mapping/SimpleAttributes2GrantedAuthoritiesMapper.java
private GrantedAuthority getGrantedAuthority(String attribute) {
		if (isConvertAttributeToLowerCase()) {
			attribute = attribute.toLowerCase(Locale.getDefault());
		}
		else if (isConvertAttributeToUpperCase()) {
			attribute = attribute.toUpperCase(Locale.getDefault());
		}
		if (isAddPrefixIfAlreadyExisting() || !attribute.startsWith(getAttributePrefix())) {
			return new SimpleGrantedAuthority(getAttributePrefix() + attribute);
		}
		else {
			return new SimpleGrantedAuthority(attribute);
		}
	}
private GrantedAuthority getGrantedAuthority(String attribute) {
		if (isConvertAttributeToLowerCase()) {
			attribute = attribute.toLowerCase(Locale.getDefault());
		}
		else if (isConvertAttributeToUpperCase()) {
			attribute = attribute.toUpperCase(Locale.getDefault());
		}
		if (isAddPrefixIfAlreadyExisting() || !attribute.startsWith(getAttributePrefix())) {
			return new SimpleGrantedAuthority(getAttributePrefix() + attribute);
		}
		else {
			return new SimpleGrantedAuthority(attribute);
		}
	}
Map the given role one-on-one to a Spring Security GrantedAuthority, optionally
doing case conversion and/or adding a prefix.

@param attribute The attribute for which to get a GrantedAuthority
@return GrantedAuthority representing the given role.