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Execution default-testResources

I was doing a project at work on a PC there, when I got home I tried to open it on my PC and I ended up encountering two errors in line 5 of the pom.xml file, my PC already gave an error when installing the new ones versions of eclipse, now this is giving error in my work project, I hope someone help me please.
error 1:
Execution default-testResources of goal org.apache.maven.plugins:maven-resources-plugin:3.2.0:testResources failed:
Unable to load the mojo 'testResources' (or one of its required components) from the plugin
'org.apache.maven.plugins:maven-resources-plugin:3.2.0'
(org.apache.maven.plugins:maven-resources-plugin:3.2.0:testResources:default-testResources:process-test-resources)
error 2:
Execution default-resources of goal org.apache.maven.plugins:maven-resources-plugin:3.2.0:resources failed:
Unable to load the mojo 'resources' (or one of its required components) from the plugin
'org.apache.maven.plugins:maven-resources-plugin:3.2.0'
(org.apache.maven.plugins:maven-resources-plugin:3.2.0:resources:default-resources:process-resources)
pom.xml file:
<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.5.3</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.example</groupId>
<artifactId>demo</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>demo</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>11</java.version>
</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-web</artifactId>
</dependency>
<dependency>
<groupId>org.postgresql</groupId>
<artifactId>postgresql</artifactId>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<optional>true</optional>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<configuration>
<excludes>
<exclude>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
</exclude>
</excludes>
</configuration>
</plugin>
</plugins>
</build>
</project>

Spring boot dependency error for some of the dependencies in maven

Below is my pom.xml
<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>com.java.hackathon</groupId>
<artifactId>com.java.hackathon</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>com.java.hackathon</name>
<url>http://maven.apache.org</url>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>1.8</java.version>
</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-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-devtools</artifactId>
<scope>runtime</scope>
<optional>true</optional>
</dependency>
<dependency>
<groupId>org.codehaus.mojo</groupId>
<artifactId>sonar-maven-plugin</artifactId>
<version>3.6.0.1398</version>
<type>pom</type>
</dependency>
<dependency>
<groupId>org.springdoc</groupId>
<artifactId>springdoc-openapi-ui</artifactId>
<version>1.5.0</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
<exclusions>
<exclusion>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
</exclusion>
</exclusions>
</dependency>
<!-- junit 5 -->
<dependency>
<groupId>org.junit.jupiter</groupId>
<artifactId>junit-jupiter-engine</artifactId>
<version>${junit-jupiter.version}</version>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
<plugin>
<groupId>org.jacoco</groupId>
<artifactId>jacoco-maven-plugin</artifactId>
<version>0.8.0</version>
<executions>
<execution>
<id>default-prepare-agent</id>
<goals>
<goal>prepare-agent</goal>
</goals>
</execution>
<execution>
<id>default-report</id>
<phase>prepare-package</phase>
<goals>
<goal>report</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
</project>
Error message i am getting is
For artifact {org.springframework.boot:spring-boot-starter-data-jpa:null:jar}: The version cannot be empty. (org.apache.maven.plugins:maven-resources-
plugin:2.6:testResources:default-testResources:process-test-resources) org.apache.maven.artifact.InvalidArtifactRTException: For artifact
{org.springframework.boot:spring-boot-starter-data-jpa:null:jar}: The version cannot be empty. at
But in most of the cases what I observed most of them wont declare any version for spring-boot-starter-data-jpa and spring-boot-starter-web but i am getting these errors I am getting errors for all the dependencies where i had not declared version
So i want to know how to resolve these errors where version has not been declared or any plugins needed to be downloaded. I am executing the code in eclipse.

Normally you don't declare dependency versions when you have defined a dependencyManagement section in your POM where you centralize all of the dependencies used by all of your modules.
Since your POM does not define a dependencyManagement, you will need to provide the version for each dependency. You can check this sample guide project from Spring Boot, where you will notice that they set a parent in the POM:
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.4.2</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
This parent will cause the POM to inherit a dependencyManagement section containing all of the versions of the spring-boot-starter-xx dependencies.
More details: https://docs.spring.io/spring-boot/docs/current/reference/html/using-spring-boot.html#using-boot-dependency-management

How to build a multi-module Maven project without a main class in one of the modules

I've been trying to find an answer to this issue in similar questions but I still don't know what is causing it.
I have a multi-module maven project and I'm trying to run mvn install or mvn package and I get the following error
[INFO] app ................................................... SUCCESS
[ 1.025 s]
[INFO] module-data ..................................... FAILURE [
0.952 s]
[INFO] module-app ...................................... SKIPPED
[ERROR] Failed to execute goal
org.springframework.boot:spring-boot-maven-plugin:2.1.1.RELEASE:repackage
(repackage) on project project-data: Execution repackage of goal
org.springframework.boot:spring-boot-maven-plugin:2.1.1.RELEASE:repackage
failed: Unable to find main class -> [Help 1]
The project-app module has a java class in the src folder, whereas the project-data module does not have a main class.
parent pom.xml
<?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>
<packaging>pom</packaging>
<modules>
<module>project-data</module>
<module>project-app</module>
</modules>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.1.1.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.example</groupId>
<artifactId>app</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>app</name>
<description></description>
<properties>
<java.version>1.8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-jdbc</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-thymeleaf</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-devtools</artifactId>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>com.h2database</groupId>
<artifactId>h2</artifactId>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<optional>true</optional>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
project-data pom.xml
<?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>app</artifactId>
<groupId>com.example</groupId>
<version>0.0.1-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>project-data</artifactId>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
<groupId>com.h2database</groupId>
<artifactId>h2</artifactId>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.postgresql</groupId>
<artifactId>postgresql</artifactId>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<optional>true</optional>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<executions>
<execution>
<goals>
<goal>repackage</goal>
</goals>
<configuration>
<skip>true</skip>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>
</project>
project-app pom.xml
<?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>app</artifactId>
<groupId>com.example</groupId>
<version>0.0.1-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>project-app</artifactId>
<dependencies>
<dependency>
<artifactId>project-data</artifactId>
<groupId>com.example</groupId>
<version>0.0.1-SNAPSHOT</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-thymeleaf</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-devtools</artifactId>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
</project>
I have something very similar to the structure of this project (sfg-pet-clinic), however, after downloading and running mvn package, it works fine. I don't see much difference between the pom files of my project and this one so what could I be missing?

Configuration is for older versions of spring.
Remove:
<configuration>
<skip>true</skip>
</configuration>
Instead, add this flag below pom artifactId
<properties>
<spring-boot.repackage.skip>true</spring-boot.repackage.skip>
</properties>
Like so:
<parent>
<artifactId>mc-pet-clinic</artifactId>
<groupId>guru.springframework</groupId>
<version>0.0.1-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>pet-clinic-data</artifactId>
<properties>
<spring-boot.repackage.skip>true</spring-boot.repackage.skip>
</properties>
...

I would move the entire
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
section from the parent to the module-app module, because that one is the single module which uses the repackage functionality.
Moreower I would delete the plugin section from the module-data too, because there is no need to repackage that module.

Thanks to #wemu on the comments section.
Adding this:
<configuration>
<mainClass> ${your.start.Class}</mainClass>
</configuration>
to the plugin section is required on version 2.1.1.RELEASE of the spring-boot-starter-parent dependency, as long as your class is in another module.
The project sfg-pet-clinic I referred to in my question uses an older version which does not need the <mainClass> configuration

Okay here is how I fixed that.
My Steps were:
Change the packaging of pom.xml file for project-data to pom from
jar (I used overview of Eclipse)
add <type>pom</type> in pom.xml file for project-app for dependency of module-data
<dependency>
<groupId>samee.springframework</groupId>
<artifactId>project-data</artifactId>
<version>0.0.1-SNAPSHOT</version>
<type>pom</type>
</dependency>
Then you can run your clean and package/install

I just changed the Spring Boot version in the parent pom.xml from 2.1.1 to 2.0.3 and it works.
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.0.3.RELEASE</version>
<relativePath /> <!-- lookup parent from repository -->
</parent>
Would be better to make it work in 2.1.1 though, but that's a quick and simple solution.

Spring boot application as dependency

My problem is that I have a multi module maven build where one part is generated by swagger as a spring boot application.
The second module should extend on the code generated and finally started.
When I compile with maven the second project does not find the classes in the generated code. I checked the jar and the class files end up in a BOOT-INF directory when building the jar.
I suspect that this is the problem. What is the best solution to compile my code.
the parent pom
<?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>
<parent>
<groupId>com.xxx</groupId>
<artifactId>applications</artifactId>
<version>0.0.1-SNAPSHOT</version>
<relativePath>../pom.xml</relativePath>
</parent>
<name>project1-connector</name>
<artifactId>project1-connector</artifactId>
<version>1.0.0-SNAPSHOT</version>
<packaging>pom</packaging>
<scm>
<developerConnection>scm:git:ssh://git#xxx.com:7999/bla/project1-java-repo.git</developerConnection>
</scm>
<properties>
<majorVersion>1</majorVersion>
<minorVersion>0</minorVersion>
</properties>
<build>
<plugins>
<plugin>
<groupId>io.swagger</groupId>
<artifactId>swagger-codegen-maven-plugin</artifactId>
<version>2.3.1</version>
<executions>
<execution>
<goals>
<goal>generate</goal>
</goals>
<configuration>
<inputSpec>${project.basedir}/src/main/resources/api.yaml</inputSpec>
<language>spring</language>
<configurationFile>${project.basedir}/src/main/resources/apiConfig.json</configurationFile>
<output>${project.basedir}/project1-api</output>
<configOptions>
<sourceFolder>src/main/java</sourceFolder>
</configOptions>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>
<modules>
<module>project1-api</module>
<module>project1-backend</module>
</modules>
project1-api generated pom.xml
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.xxx</groupId>
<artifactId>project1-api</artifactId>
<packaging>jar</packaging>
<name>project1-api</name>
<version>1.0.1</version>
<properties>
<java.version>1.8</java.version>
<maven.compiler.source>${java.version}</maven.compiler.source>
<maven.compiler.target>${java.version}</maven.compiler.target>
<springfox-version>2.7.0</springfox-version>
</properties>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.5.9.RELEASE</version>
</parent>
<build>
<sourceDirectory>src/main/java</sourceDirectory>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<executions>
<execution>
<goals>
<goal>repackage</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-tomcat</artifactId>
</dependency>
<!--SpringFox dependencies -->
<dependency>
<groupId>io.springfox</groupId>
<artifactId>springfox-swagger2</artifactId>
<version>${springfox-version}</version>
</dependency>
<dependency>
<groupId>io.springfox</groupId>
<artifactId>springfox-swagger-ui</artifactId>
<version>${springfox-version}</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.datatype</groupId>
<artifactId>jackson-datatype-jsr310</artifactId>
</dependency>
<!-- Bean Validation API support -->
<dependency>
<groupId>javax.validation</groupId>
<artifactId>validation-api</artifactId>
</dependency>
</dependencies>
</project>
project1-backend pom.xml
http://maven.apache.org/xsd/maven-4.0.0.xsd">
4.0.0
<groupId>com.xxx</groupId>
<artifactId>project1-backend</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>project1-backend</name>
<description>Project1 Connection</description>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.0.1.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<java.version>9</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-batch</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-integration</artifactId>
</dependency>
<dependency>
<groupId>org.liquibase</groupId>
<artifactId>liquibase-core</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.springframework.batch</groupId>
<artifactId>spring-batch-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>com.xxx</groupId>
<artifactId>project1-api</artifactId>
<version>1.0.1</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>

As stated here:
https://happilyblogging.wordpress.com/2017/07/31/using-spring-boot-application-as-dependency-in-another-spring-boot-application-project/
The problem is in the generated pom.xml.
If I add the configuration part to the project1-api spring-boot plugin part, it works.
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<executions>
<execution>
<goals>
<goal>repackage</goal>
</goals>
<configuration>
<classifier>exec</classifier>
</configuration>
</execution>
</executions>
</plugin>

Spring Boot application is not executable

I am migrating my old Spring setup to Spring Boot 1.5.1.RELEASE.
I'm failing to get an executable .jar, I followed countless examples but my jar fails to become an executable.
It's a multi-module setup so here is my parent pom.xml
<?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/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.xyz</groupId>
<artifactId>xyz</artifactId>
<name>xyz</name>
<version>1.0.0</version>
<packaging>pom</packaging>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.5.1.RELEASE</version>
</parent>
<properties>
<java.version>1.8</java.version>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<commons.version>3.5</commons.version>
<guava.version>21.0</guava.version>
</properties>
<modules>
<module>mainApp</module>
<module>module1</module>
<module>module2</module>
..........
</modules>
<dependencyManagement>
<dependencies>
<!-- Spring boot -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter</artifactId>
</dependency>
<!-- commons -->
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-lang3</artifactId>
<version>3.5</version>
</dependency>
<!-- google guava -->
<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
<version>${guava.version}</version>
</dependency>
<!-- Test -->
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
</dependencyManagement>
</project>
This is the pom of the mainApp, it is the module that has Application.java which holds main method.
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<artifactId>xyz</artifactId>
<groupId>com.xyz</groupId>
<version>1.0.0</version>
</parent>
<artifactId>mainApp</artifactId>
<groupId>com.xyz.mainApp</groupId>
<packaging>jar</packaging>
<name>mainApp</name>
<dependencies>
<!-- Spring Boot -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<!-- Spring Security OAuth2-->
<dependency>
<groupId>org.springframework.security.oauth</groupId>
<artifactId>spring-security-oauth2</artifactId>
</dependency>
<!-- xyz dependencies -->
<dependency>
<groupId>com.xyz.module3</groupId>
<artifactId>module3</artifactId>
<version>${project.version}</version>
</dependency>
<dependency>
<groupId>com.xyz.module2</groupId>
<artifactId>module2</artifactId>
<version>${project.version}</version>
</dependency>
</dependencies>
<build>
<pluginManagement>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<configuration>
<executable>true</executable>
</configuration>
</plugin>
</plugins>
</pluginManagement>
<finalName>xyz</finalName>
</build>
</project>
Things that work:
So things work okay when I do mvn clean install in the folder of parent pom.xml and then run mvn spring-boot:run in the mainApp folder
Things that fail:
when I execute java -jar mainApp/target/xyz.jar I get an error like:
no main manifest attribute, in mainApp/target/xyz.jar
if I attempt to run the jar like ./mainApp/target/xyz.jar, well I can't as the file is not an executable, my macOS Sierra terminal shows this for file permissions:
-rw-r--r-- 1 userXYZ staff 37641156 Feb 1 13:14 xyz.jar
If I manually change the permissions to -rwxr--r-- and attempt to run the file I get this gibberish:
/xyz.jar: line 1: PK: command not found
./xyz.jar: line 2: syntax error near unexpected token `)'
./xyz.jar: line 2: ?iAJ META-INF?iAJMETA-INF/MANIFEST.MFu??J?0??y?y??,??nW*???Jb3?F?LI?????qa?n?3???)Mp5&V????ñ^IQ?????ޱ?.#??`?$?{<??7?m6?j܀?W????'????γڎ9?>????RT?͡?V??
G??
3iR?G4???dә?A(̀?z?ϖV]ٷ??T??O>?^??0wy?u?^??S]?iG?2?"???i?$?'

The problem is not how the plugin is configured, but where the plugin is configured.
I have wrapped my plugins with <pluginManagement>, which was causing all the problems, when i removed it all was resolved and worked perfectly

update your build block in pom.xml with following, make sure you are using using Maven 3.2 (or better):
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<version>1.5.1.RELEASE</version>
<executions>
<execution>
<goals>
<goal>repackage</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>

the main class entry is missing in the jar manifesto.
Please modify the boot maven plugin as below:
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<configuration>
<mainClass>${start-class}</mainClass>
<layout>ZIP</layout>
</configuration>
<executions>
<execution>
<goals>
<goal>repackage</goal>
</goals>
</execution>
</executions>
</plugin>
Plugin info