Creating a war file in Spring Boot is not difficult.
It already supports by default 2 plugins for traditional deployment:
1.spring-boot-gradle-plugin
2.spring-boot-maven-plugin
The first step for the migration is to provide a SpringBootServletInitializer subclass and override its configure method. All of that is done in your @SpringBootApplication class.
The Second step is to set up you build file e.g. pom.xml, build.gradle, with the correct extension for the war file:
Maven: war
Gradle: apply plugin: 'war'
The Third step is to ensure that the embedded servlet container doesn’t interfere with the servlet container to which the war file will be deployed:
Maven:
org.springframework.boot
spring-boot-starter-tomcat
provided
Gradle: providedRuntime 'org.springframework.boot:spring-boot-starter-tomcat'
The last but not least is to DELETE the current applicationContext.xml. If you keep the the context.xml the application will start and shutdown immediately, sometimes the error will be silent making it difficult to find the root cause.