Maven supports multi-module applications by having the child modules point to the parent module, but Spring Boot wants it's parent to be
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.2.0.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
According to the Spring docs I can still do this (use a maven parent-child relationship) if I add dependency management like this:
<dependencyManagement>
<dependencies>
<dependency>
<!-- Import dependency management from Spring Boot -->
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-dependencies</artifactId>
<version>2.2.0.RELEASE</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
instead of the Spring Boot parent.
I've done this, but now my unit tests don't run when I run mvn from the command line. The unit tests still work from Intellij, but something in the new parent-child / changes is confusing mvn and keeping it from running tests.
Here's a pom.xml from a module that no longer runs its tests:
<project xmlns=...>
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>abcd</groupId>
<artifactId>abcd.parent</artifactId>
<version>0.0.1-SNAPSHOT</version>
</parent>
<artifactId>entities</artifactId>
<name>entities</name>
<description>Entities and Repositories</description>
<properties>
<maven.compiler.target>11</maven.compiler.target>
<maven.compiler.source>11</maven.compiler.source>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>com.h2database</groupId>
<artifactId>h2</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
<dependencyManagement>
<dependencies>
<dependency>
<!-- Import dependency management from Spring Boot -->
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-dependencies</artifactId>
<version>2.2.0.RELEASE</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
</project>
This module is a library module that does not contain a @SpringBootApplication but the tests ran before converting to the maven parent-child structure.
Edit:
This project has both junit 4 and junit-jupiter-api 5.5.2 in its dependencies. When using org.junit.jupiter.api.Test (5.5.2) no tests run. When using org.junit.Test (4.12) the test runs but the Autowired repository doesn't get injected (null). (The Autowired repository is in another module.)
Spring doesn't handle dependencies correctly when using a normal maven child-parent structure.