Adding a Context Path to a Spring Boot Application

To programmatically set a context root for a Spring Boot application, you can use the EmbeddedServletContainerFactory bean. This bean allows you to customize the servlet container used by the application.

In the provided example, you've created a custom EmbeddedServletContainerFactory bean called servletContainer() that sets the context path to /mainstay. However, the issue is that the Spring Boot auto-configuration detects your custom bean and overrides the context path with the default value (an empty string).

To resolve this issue, instead of creating a custom EmbeddedServletContainerFactory bean, you can simply add the following properties to your application.properties file:

server.servlet.context-path=/mainstay
server.port=12378

This will configure the application to use /mainstay as the context path and listen on port 12378. Alternatively, you can still use the EmbeddedServletContainerCustomizer interface if you need to perform additional customizations to the servlet container.