Multi-module spring boot configuration

Question

I'm trying to configure a multi-module Spring boot application. The simplest example is:

pom1

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>testExample</groupId>
    <artifactId>testExample</artifactId>
    <packaging>pom</packaging>
    <version>1.0-SNAPSHOT</version>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.2.RELEASE</version>
        <relativePath/>
    </parent>

    <build>
        <plugins>
            <plugin>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.1</version>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                </configuration>
            </plugin>
        </plugins>
    </build>

    <modules>
        <module>module1</module>
    </modules>


</project>

pom2:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <parent>
        <artifactId>testExample</artifactId>
        <groupId>testExample</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <packaging>jar</packaging>

    <artifactId>module1</artifactId>

    <properties>
        <start-class>testExamplePackage.RootConfig</start-class>
    </properties>

    <build>
        <plugins>
            <plugin>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.1</version>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>
    </dependencies>


</project>

RootConfig:

package testExamplePackage;

import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class RootConfig {

    public static void main(String[] args) {
        System.out.println("Doing some work...");
    }
}

Why am I getting an ERROR starting maven 'clean spring-boot:run'?

"C:\Program Files\Java\jdk1.8.0_102\bin\java" -Dmaven.multiModuleProjectDirectory=D:\PROGRAMACION\Projects\TEMP_PROJECTS\testExample "-Dmaven.home=C:\Program Files (x86)\JetBrains\IntelliJ IDEA 2017.1\plugins\maven\lib\maven3" "-Dclassworlds.conf=C:\Program Files (x86)\JetBrains\IntelliJ IDEA 2017.1\plugins\maven\lib\maven3\bin\m2.conf" "-javaagent:C:\Program Files (x86)\JetBrains\IntelliJ IDEA 2017.1\lib\idea_rt.jar=57646:C:\Program Files (x86)\JetBrains\IntelliJ IDEA 2017.1\bin" -Dfile.encoding=UTF-8 -classpath "C:\Program Files (x86)\JetBrains\IntelliJ IDEA 2017.1\plugins\maven\lib\maven3\boot\plexus-classworlds-2.5.2.jar" org.codehaus.classworlds.Launcher -Didea.version=2017.1 clean spring-boot:run
[INFO] Scanning for projects...
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Build Order:
[INFO] 
[INFO] testExample
[INFO] module1
[INFO]                                                                         
[INFO] ------------------------------------------------------------------------
[INFO] Building testExample 1.0-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO] 
[INFO] --- maven-clean-plugin:2.6.1:clean (default-clean) @ testExample ---
[INFO] 
[INFO] >>> spring-boot-maven-plugin:1.5.2.RELEASE:run (default-cli) > test-compile @ testExample >>>
[INFO] 
[INFO] <<< spring-boot-maven-plugin:1.5.2.RELEASE:run (default-cli) < test-compile @ testExample <<<
[INFO] 
[INFO] --- spring-boot-maven-plugin:1.5.2.RELEASE:run (default-cli) @ testExample ---
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Summary:
[INFO] 
[INFO] testExample ........................................ FAILURE [  0.487 s]
[INFO] module1 ............................................ SKIPPED
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 0.884 s
[INFO] Finished at: 2017-03-25T16:44:47+02:00
[INFO] Final Memory: 18M/220M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.springframework.boot:spring-boot-maven-plugin:1.5.2.RELEASE:run (default-cli) on project testExample: Unable to find a suitable main class, please add a 'mainClass' property -> [Help 1]
[ERROR] 
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR] 
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoExecutionException

Process finished with exit code 1

It wants mainClass, but this class is already specified.

Answer 1

This is how I do it.

From the root of the multi-module project, run this:

mvn -pl module1 spring-boot:run

Now, if you have a config folder in the root of your multi-module spring boot project, Spring-boot will also scan that folder for property files (n addition to src/main/resources), making those properties global to all your modules.

Answer 2

mvn clean spring-boot:run has to be executed from the module that contains the SpringBootApplication.
You execute it from the parent pom.

Execute this command from module1, it should work.

By the way, this duplicated declaration in module1 pom.xml is not required as it is already specified by your parent :

 <build>
    <plugins>
        <plugin>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>3.1</version>
            <configuration>
                <source>1.8</source>
                <target>1.8</target>
            </configuration>
        </plugin>
    </plugins>
</build>