Deploying SpringBoot (rest services) war via IntelliJ on Tomcat gives 404's - maven

Question

Starting a small SpringBoot application by running the application (directly), the REST service localhost:8080/xyz/a gives a correct JSON result.
Via IntelliJ I configured a Tomcat server. I added this WAR with a context root of '/contextroot'. So I expected the URL REST to be localhost:8080/contextroot/xyz/a. This keeps on getting 404 errors.
Can you help me getting the right configuration or URL?
Is there a way to see which URL's are mapped from the controller to the URL's? Or: how can I solve these mapping issues more easily (from Tomcat)?
In the Maven Pom.xml I have:
<groupId>nl.xyz</groupId>
<artifactId>contextroot</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>contextroot</name>
<packaging>war</packaging>
The within is also contextroot.

Answer 1

#Jonhib - thank you for helping.
The problem was the way I deployed a SpringBoot (jar) application as a WAR.
Take these 3 steps to change a SpringBoot standard application into a deployable (old fashioned) WAR. This is needed because I deploy it together with a Angular4 application.
Step 1 - Change the standard SpringBoot application:
#SpringBootApplication
public class Application extends SpringBootServletInitializer {
#Override
protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
return application.sources(Application .class);
}
public static void main(String[] args) {
SpringApplication.run(Application .class, args);
}
}
Change the target of the building process from 'jar' into a 'war'.
<packaging>war</packaging>
Add a new dependency into the pom.xml maven file:
<dependencies>
...
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-tomcat</artifactId>
<scope>provided</scope>
</dependency>
...
</dependencies>