It was when I was developing a Servlet using Tomcat 8.5.37. Suddenly
note: further occurrences of http header parsing errors will be logged at debug level.
java.lang.IllegalArgumentException: Invalid character found in method name. HTTP method names must be tokens
Error occurred. At that time https://localhost:8080/プロジェクト名 I was accessing it with, but I solved it by changing this to http: //.