I am using Spring Boot to create a web app, and I am not sure how to change the URL from localhost:8080 to something like localhost:8080/myWebApp.
In your src/main/resources put an application.properties or application.yml and put a server.contextPath in there.
server.contextPath=/your/context/here
When starting your application the application will be available at http://localhost:8080/your/context/here.
For a comprehensive list of properties to set see Appendix A. of the Spring Boot reference guide.
Instead of putting it in the application.properties you can also pass it as a system property when starting your application
java -jar yourapp.jar -Dserver.contextPath=/your/path/here