My operating system is Ubuntu 16.04.3 LTS , and I downloaded the latest version of Tomcat, 8.55.
I have configured apache2 and Tomcat so that Tomcat runs on https, however I have a file in /opt/tomcat/webapp/archivo.jsp that when I try to execute it in https://localhost/webapp/archivo.jsp it does not load me and it returns a 404.
You can not load a loose JSP file into an application container, you have to declare an application (with a web.xml file), exposing the servlets that are to be executed. This is usually packaged in a war file that is what is displayed on the server.
The simplest solution is to save the file prueba.jsp in the directory / opt / tomcat / webapp / examples, as the image shows: link