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Non-resolvable parent POM-Could not transfer artifact

I am new Java developer.I tried to load the build after generating from spring intializer.Receiving the following error while trying to import maven project.
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 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>3.0.1</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>dev.example.restapi</groupId>
<artifactId>dev.restapi.proj</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>dev.restapi.proj</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>17</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-security</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.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.springframework.security</groupId>
<artifactId>spring-security-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>
I tried Maven update , mvn clean install problem is not yet solved.
I tried mvn -U build as suggested
Error received is
[ERROR] Non-resolvable parent POM for dev.example.restapi:dev.restapi.proj:0.0.1-SNAPSHOT: Could not transfer artifact org.springframework.boot:spring-boot-starter-parent:pom:3.0.1 from/to central (https://repo.maven.apache.org/maven2): transfer failed for https://repo.maven.apache.org/maven2/org/springframework/boot/spring-boot-starter-parent/3.0.1/spring-boot-starter-parent-3.0.1.pom and 'parent.relativePath' points at no local POM # line 5, column 10: Connection reset by peer ->

spring multi-module project starting

i am using spring framework to produce a web application .
i prefered to use multi module project to make my app readable .
this is the hierarchy of my project
my parent project 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 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>2.5.6</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.ireview</groupId>
<artifactId>IReviewParent</artifactId>
<version>1.0-SNAPSHOT</version>
<packaging>pom</packaging>
<name>demo</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>11</java.version>
<ireview.version>${project.version}</ireview.version>
<start-class>ireview.DemoApplication</start-class>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>jakarta.persistence</groupId>
<artifactId>jakarta.persistence-api</artifactId>
<version>2.2.3</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.springframework.boot/spring-boot-starter-test -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<version>2.5.6</version>
<scope>test</scope>
</dependency>
<!-- https://mvnrepository.com/artifact/org.springframework.boot/spring-boot-starter-web -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
<version>2.5.6</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.springframework.boot/spring-boot-devtools -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-devtools</artifactId>
<version>2.5.6</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.springframework.boot/spring-boot-starter-mail -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-mail</artifactId>
<version>2.5.6</version>
</dependency>
</dependencies>
<modules>
<module>IReview-exceptions</module>
<module>IReview-domain</module>
<module>IReview-data</module>
<module>IReview-api</module>
<module>IReview-security</module>
<module>IReview-main</module>
</modules>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<configuration>
<skip>false</skip>
<!-- <jmxPort>9001</jmxPort>-->
</configuration>
</plugin>
</plugins>
</build>
</project>
when i launch my app from intellij it starts well , but the problem occurs when i try to launch it from command line with (mvn spring-boot:start) the error below appears
[ERROR] Failed to execute goal org.springframework.boot:spring-boot-maven-plugin:2.5.6:start (default-cli) on project IReviewParent: Could not contact Spring Boot application: Failed to retrieve RMIServer stub: javax.naming.CommunicationException [Root exception is java.rmi.UnmarshalException: Error unmarshaling return header; nested exception is:
[ERROR] java.net.SocketException: Connection reset]
also i want to know . if i want to host my app i need a jar to put it in the host , where do i get it from ? how to launch it from cmd line ?
please help !!!!

To launch it from command line run:
mvn spring-boot:run
The jar you can find inside /target directory

Maven - Failed to execute goal org.springframework.boot:spring-boot-maven-plugin:2.4.1:run

I created my project at https://start.spring.io/
Several errors on the internet are similar but did not solve my problem.
when executing it I found an error return:
Failed to execute goal org.springframework.boot: spring-boot-maven-plugin: 2.4.1: run
Here are my POM and main file main
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 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>2.4.1</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>net.javaguides</groupId>
<artifactId>spring-boot-restfull-webservice</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>spring-boot-restfull-webservice</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>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>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
Class:
package net.javaguides.springboot;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
#SpringBootApplication
public class SpringBootRestfullWebserviceApplication {
public static void main(String[] args) {
SpringApplication.run(SpringBootRestfullWebserviceApplication.class, args);
}
}
I'm new to Springboot, how do I fix it?

I've gotten your build to work, but I had to make some compromises.
I looked at the Spring documentation for what you are trying:
https://spring.io/guides/gs/rest-service/
Then I looked at the pom.xml for the example:
https://github.com/spring-guides/gs-rest-service/blob/master/complete/pom.xml
Despite the fact that the documentation says you can use Java 1.8 or higher, you need to use 1.8. If you go higher, you have to specify the property encoding in the plugin, and you can't do that because you are using the Spring Boot plugin rather than a plugin you can configure in the pom.xml for your project.
I also added a lower version of the maven-surefire-plugin than Spring Boot uses. With this version, you get the error [ERROR] There are test failures, but you are not running any tests.
I commented out the MySql and JPA dependencies, which won't work unless you have database connection settings.
<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>2.4.1</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>net.javaguides</groupId>
<artifactId>spring-boot-restful-webservice</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>spring-boot-restful-webservice</name>
<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>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>org.junit.vintage</groupId>
<artifactId>junit-vintage-engine</artifactId>
</exclusion>
</exclusions>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-surefire-plugin</artifactId>
<version>2.5</version>
<configuration>
<skipTests>false</skipTests>
<testFailureIgnore>true</testFailureIgnore>
<forkMode>once</forkMode>
</configuration>
</plugin>
</plugins>
</build>
</project>

In my case i was running the jar file when i was activated maven install. The made it unable to delete and create a new jar as one was already running. After i quit running the jar file. I was able to build the project. sometimes reading error messages helps

Try to read well the exception log in cli, after executing your "mvn spring-boot:run" command.
It can be a due to
a connection with your DB, for example mysql not started
Or started but the DB name is not correct in your application.properties file e.g. java.sql.SQLSyntaxErrorException: Unknown database
Or even the password used of the db user is not correct in the application.properties file: e.g Caused by: java.sql.SQLNonTransientConnectionException: Public Key Retrieval is not allowed
so analyze first your logs before modifying java version, xml elements in the plugin ...
Normally this follwing generic pom.xml is enough to have maven running successfully your tomcat server (embedded in spring boot):
<?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>2.7.2</version>
<relativePath />
</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>17</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>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>org.junit.vintage</groupId>
<artifactId>junit-vintage-engine</artifactId>
</exclusion>
</exclusions>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>

Maven not picking up the classes from dependency modules

In my spring-boot project there are two microservices, one config-server, and one naming server. It also has two modules which I am adding as a dependency in the microservices.
Below is the pom of the commons-new module which should be a dependency in my microservices.
<?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>2.3.0.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.highpeak.tlp</groupId>
<artifactId>commons-new</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>commons-new</name>
<description>Contains common modules needed by all the microservices</description>
<properties>
<java.version>1.8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter</artifactId>
</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>
<exclusions>
<exclusion>
<groupId>org.junit.vintage</groupId>
<artifactId>junit-vintage-engine</artifactId>
</exclusion>
</exclusions>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-web</artifactId>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
And I am adding it as a dependency in my microservice.
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://maven.apache.org/POM/4.0.0"
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>2.3.0.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.highpeak.tlp</groupId>
<artifactId>ybanq-auth-manager</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>ybanq-auth-manager</name>
<description>Manages the authentication process with ybanq</description>
<properties>
<java.version>1.8</java.version>
<spring-cloud.version>Hoxton.SR4</spring-cloud.version>
<maven.compiler.source>1.8</maven.compiler.source>
<maven.compiler.target>1.8</maven.compiler.target>
<maven.compiler.testSource>1.8</maven.compiler.testSource>
<maven.compiler.testTarget>1.8</maven.compiler.testTarget>
</properties>
<dependencies>
<dependency>
<groupId>com.highpeak.tlp</groupId>
<artifactId>commons-new</artifactId>
<version>0.0.1-SNAPSHOT</version>
<scope>compile</scope>
</dependency>
<dependency>
<groupId>com.highpeak.tlp</groupId>
<artifactId>redis-common</artifactId>
<version>0.0.1-SNAPSHOT</version>
<scope>compile</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-config</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-openfeign</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-devtools</artifactId>
<scope>runtime</scope>
<optional>true</optional>
</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>
<exclusions>
<exclusion>
<groupId>org.junit.vintage</groupId>
<artifactId>junit-vintage-engine</artifactId>
</exclusion>
</exclusions>
</dependency>
</dependencies>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-dependencies</artifactId>
<version>${spring-cloud.version}</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<source>1.8</source>
<target>1.8</target>
</configuration>
</plugin>
</plugins>
</build>
</project>
When I try to build the microservice using the command mvn clean install, it is throwing compiler-error message.
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.8.1:compile (default-compile) on project ybanq-auth-manager: Compilation failure: Compilation failure:
[ERROR] /Users/sandeshaj/Documents/Bitbucket/lawshram-payments/ybanq-auth-manager/src/main/java/com/highpeak/tlp/ybanqauthmanager/controller/AuthController.java:[3,42] package com.highpeak.tlp.commons.exception does not exist
[ERROR] /Users/sandeshaj/Documents/Bitbucket/lawshram-payments/ybanq-auth-manager/src/main/java/com/highpeak/tlp/ybanqauthmanager/controller/AuthController.java:[4,37] package com.highpeak.tlp.commons.util does not exist
[ERROR] /Users/sandeshaj/Documents/Bitbucket/lawshram-payments/ybanq-auth-manager/src/main/java/com/highpeak/tlp/ybanqauthmanager/service/AuthManagerService.java:[3,42] package com.highpeak.tlp.commons.exception does not exist
[ERROR] /Users/sandeshaj/Documents/Bitbucket/lawshram-payments/ybanq-auth-manager/src/main/java/com/highpeak/tlp/ybanqauthmanager/service/AuthManagerService.java:[11,51] cannot find symbol
[ERROR] symbol: class DataException
[ERROR] location: interface com.highpeak.tlp.ybanqauthmanager.service.AuthManagerService
[ERROR] /Users/sandeshaj/Documents/Bitbucket/lawshram-payments/ybanq-auth-manager/src/main/java/com/highpeak/tlp/ybanqauthmanager/service/AuthManagerServiceImpl.java:[19,42] package com.highpeak.tlp.commons.exception does not exist
However, in IntelliJ editor those classes are accessible and Intellij is not showing the compiler error. But when I run the app in IntelliJ, it shows the same errors.
What is the mistake I am making? Since I added the module as dependency their classes should be available, right?
My system maven version is 3.5.4.

The Spring Boot plugin package up all dependency jars and pulls them into the jar your module builds. The structure of this jar is specifically for Spring Boot runnable applications and is not compatible with the normal jar structures, so you can't use a Spring Boot Application jar as maven dependency jar.

Remove spring boot plugin from submodule (common-new).
I had similar issue, but with gradle and found this Unresolved Dependency on package in subproject
Unfortunately, I don't know what is exact issue in "using" spring boot plugin in submodules/subprojects.

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.