Spring boot with maven multi module project - spring-boot

Question

I have a maven multi module project designed like the first answer in following SO post:
Multi-module maven with Spring Boot
Now I want a common maven module that can contain some models to be used by multiple microservices. If I make this common project as a child of the first level parent pom (so that all dependencies injected by boot like jpa, jackson etc are available to common), then STS/Spring is detecting it as a boot application and complains about no Main class on maven build.
Can someone suggest how I can achieve this?
Current Code:
parent pom.xml: (Only relevant parts included)
<project>
<name>...</name>
<groupId>...</groupId>
<artifactId>...</artifactId>
<packaging>pom</packaging>
<version>...</version>
<parent>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-parent</artifactId>
<version>Brixton.M3</version>
<relativePath />
</parent>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
<exclusions>
<exclusion>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-tomcat</artifactId>
</exclusion>
</exclusions>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-jetty</artifactId>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<executions>
<execution>
<goals>
<goal>repackage</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
</project>
child (common module) pom.xml (only relevant parts), not to be boot app:
<project>
<artifactId>...</artifactId>
<version>...</version>
<name>...</name>
<parent>
<groupId>...</groupId>
<artifactId>...</artifactId>
<version>...</version>
</parent>
</project>

Answer 1

I don't have all the details regarding your project but my best guess is that the spring-boot-maven-plugin is defined on the parent (or you are using the spring-boot-starter-parent in your root pom). This effectively ask the build to package your module as a Spring Boot app (which is not what you want).
STS probably looks for that hint to figure out if a module contains a Spring Boot application or not. Maybe it would be nicer if it looks for a main class annotated with #EnableAutoConfiguration (or SpringBootApplication).
You can fix the problem easily (from the build side) by specifying the skip property of the repackage goal
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<configuration>
<skip>true</skip>
</configuration>
</plugin>
If STS still picks up the module as a Spring Boot app, I'd create an issue in their tracker

Answer 2

Normally, Spring Boot won't start a web container if it's not present in the module.
I would suggest you to analyse your dendencies using the command
mvn dependency:tree
One more brute-force way of ensuring is use this configuration in your application.properties
spring.main.web-environment=false

Answer 3

Here are two ways to fix this:
You can add the skip property like #Stephane Nicoll mentioned. However, this will completely ignore the test cases inside that module. https://docs.spring.io/spring-boot/docs/current/maven-plugin/examples/it-skip.html
Another option is to add a classifier property to make a separate executable jar out of this module. https://docs.spring.io/spring-boot/docs/current/maven-plugin/examples/repackage-classifier.html
<executions>
<execution>
<id>repackage</id>
<goals>
<goal>repackage</goal>
</goals>
<configuration>
<classifier>exec</classifier>
</configuration>
</execution>
This fix will make sure the dependent module get its required jar and the source module will still be an executable one.