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spring-boot Maven: How to create executable jar with main class?

Recently, I wrote a Spring-Boot project and I wanted that Maven will be able to create a jar file that I'll be able to run by the command "java -jar ".
This is the pom.xml I wrote:
<?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>SpringBootGame</groupId>
<artifactId>SpringBootGame</artifactId>
<version>1.0-SNAPSHOT</version>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
<version>2.0.3.RELEASE</version>
</dependency>
</dependencies>
<properties>
<java.version>1.8</java.version>
</properties>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<version>2.0.3.RELEASE</version>
<configuration>
<mainClass>com.game.Main</mainClass>
</configuration>
</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>
In order to build the jar file, I had to run the command: "mvn clean package spring-boot:repackage".
My questions are:
Why must I add spring-boot-maven-plugin? I already have spring-boot-starter-web dependency that adds spring-boot as a dependency and maven-compiler-plugin that builds a jar file from the code?
Can you think about a way to configure pom.xml file that I'll be able to get the jar file using the "native" command "mvn clean package" and not the cumbersome "mvn clean package spring-boot:repackage"?
Thanks

Why must I add spring-boot-maven-plugin? I already have spring-boot-starter-web dependency that adds spring-boot as a dependency and maven-compiler-plugin that builds a jar file from the code?
Because the plugin is what adds Maven support for Spring Boot
Can you think about a way to configure pom.xml file that I'll be able to get the jar file using the "native" command "mvn clean package" and not the cumbersome "mvn clean package spring-boot:repackage"?
It looks like you are missing the <packaging>jar</packaging> element in between your <project> </project> element.
The reason you had to run that lengthy command, is because you did not include the <executions></executions> element when including the plugin. Please see section 71.1 of the following docs:
https://docs.spring.io/spring-boot/docs/current/reference/html/build-tool-plugins-maven-plugin.html#build-tool-plugins-include-maven-plugin
71.2 elaborates on the <packaging> element.

In the configuration of the maven plugin you have already in place, you need to add the executable block like :
<configuration>
<executable>true</executable>
</configuration>
this will create in the target folder the runnable jar that can be run by using java -jar command.

Running Java program using mvn through command line

I am trying to run my java program TopicPublisher.java via command line. There are several dependencies specified through Maven.
In the directory with the pom.xml file, I ran the following commands: mvn clean, mvn package, and java -cp target/SOM_Enrichment-1.0-SNAPSHOT.jar TopicPublisher.
I get the following error:
Error: A JNI error has occurred, please check your installation and try again
Exception in thread "main" java.lang.NoClassDefFoundError: om/solacesystems/jcsmp/JCSMPStreamingPublishEventHandler
Below is a screenshot of my directory tree:
Any ideas how to solve this?
[EDIT]
Pom File:
<?xml version="1.0" encoding="UTF-8"?>
http://maven.apache.org/xsd/maven-4.0.0.xsd">
4.0.0
<groupId>CAMM</groupId>
<artifactId>SOM_Enrichment</artifactId>
<version>1.0-SNAPSHOT</version>
<build>
<plugins>
<plugin>
<artifactId>maven-assembly-plugin</artifactId>
<version>3.1.0</version>
<configuration>
<descriptorRefs>
<descriptorRef>jar-with-dependencies</descriptorRef>
</descriptorRefs>
</configuration>
<executions>
<execution>
<id>make-assembly</id> <!-- this is used for inheritance merges -->
<phase>package</phase> <!-- bind to the packaging phase -->
<goals>
<goal>single</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
<dependencies>
<dependency>
<groupId>com.solacesystems</groupId>
<artifactId>sol-jcsmp</artifactId>
<version>[10,)</version>
</dependency>
</dependencies>

Your program loads classes from the com.solacesystems dependency in your pom.xml, but your classpath only contains your build artifact jar. Build a fat jar, as #Kerry suggests, or use the exec-maven-plugin to run from the command line. From within your project directory (where you execute mvn package), execute:
mvn exec:java -Dexec.mainClass=TopicPublisher
The plugin builds the classpath argument from the dependencies defined in your pom. See https://www.mojohaus.org/exec-maven-plugin/ for more options.

Without seeing your full POM.xml I am assuming you have not build the final artifact to be a 'fat jar'. By this I mean that the JAR not only contains your own classes but all the third party dependencies.
You would need to use something like the Maven assembly plugin or the Maven shade pluginto do this for you. From the screenshot though I see you are using IntelliJ so you should also be able to run through your IDE obviously for just testing purposes.

mvn exec:java doesn't set classpath properly

I'm trying to run a Java program with Maven on the commandline, but it is not putting the correct entries on the classpath. If I run the program in IntelliJ (which has Maven support), the classpath has 80 or so entries including my project's jar dependencies, the compile program classes, and the resources from src/main/resources. If I run the program with mvn exec:java, I only get one entry for apache-maven-3.0.4/boot/plexus-classworlds-2.4.jar. There are no references to plexus in my entire project tree. Where is this entry coming from and why are the other expected classpath entries not there?
Maven version: Apache Maven 3.0.4 (r1232337; 2012-01-17 00:44:56-0800)
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.example</groupId>
<artifactId>MyProject</artifactId>
<version>SNAPSHOT</version>
<packaging>jar</packaging>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
<dependencies>
<!-- lots of dependencies -->
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>2.5.1</version>
<configuration>
<source>1.7</source>
<target>1.7</target>
<showDeprecation>true</showDeprecation>
<showWarnings>true</showWarnings>
<executable>${env.JAVA_HOME}/bin/javac</executable>
<fork>true</fork>
</configuration>
</plugin>
<plugin>
<artifactId>maven-assembly-plugin</artifactId>
<configuration>
<descriptors>
<descriptor>${basedir}/src/assembly/assembly.xml</descriptor>
</descriptors>
<appendAssemblyId>false</appendAssemblyId>
</configuration>
</plugin>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>exec-maven-plugin</artifactId>
<version>1.1</version>
<configuration>
<mainClass>com.example.MyApp</mainClass>
<executable>${env.JAVA_HOME}/bin/java</executable>
</configuration>
</plugin>
</plugins>
</build>
</project>

By default, the exec:java uses the 'runtime' scope, which will not bring your dependencies set with the 'compile' scope.
You can use:
exec:java -Dexec.classpathScope="compile"
To include the compile dependencies (not 100% sure about the -D syntax, but the variable is exec.classpathScope for sure).
This should do the trick.
If you need more info/options, the plugin page has some options listed: http://mojo.codehaus.org/exec-maven-plugin/java-mojo.html

I don't know about Plexus (I would guess it is a dependency of the Exec Maven Plugin?) , but try running with debugging turned on: mvn exec:java -X and it should be more clear that your dependencies are being added to the classpath:
....
[DEBUG] Invoking : com.example.MyApp.main()
[DEBUG] Plugin Dependencies will be excluded.
[DEBUG] Project Dependencies will be included.
[DEBUG] Collected project artifacts [log4j:log4j:jar:1.2.16:compile, commons-lang:commons-lang:jar:2.6:compile]
[DEBUG] Collected project classpath [C:\MyProject\target\classes]
[DEBUG] Adding to classpath : file:/C:/MyProject/target/classes/
[DEBUG] Adding project dependency artifact: log4j to classpath
[DEBUG] Adding project dependency artifact: commons-lang to classpath
....
You should see lots of the "Adding project dependency artifact" messages.

Maven: how to do runable jar (uberjar) with included external libraries

Until now i made runnable jars with Ant and there were no problems with it.
However i now try to mavenize my project and i realy can't figured out how to do runable jar with this tool.
I've read tons of tutorials (also here, on Stackoverflow), helps, advices and... nothing. In my case all of them don't work which probably means i don't understand some basics.
I have such simple project:
This is app, witch use mysql-connector-java-5.1.24-bin.jar (placed in 'lib' dir) to connect to MySQL database.
I want to include this jar into final jar (DBPreformatter.jar).
I used assembly and shaded plugins in many configurations, but they NEVER added this jar into DBPreformatter.jar.
This is my pom.xml:
<modelVersion>4.0.0</modelVersion>
<groupId>com.icd4you</groupId>
<artifactId>DBPreformatter</artifactId>
<version>1.0.0</version>
<name>DBPreformatter</name>
<description>DB processing and cleaning tool</description>
<packaging>jar</packaging>
<dependencies>
<dependency>
<groupId>mysql-connector-java-5.1.24-bin</groupId>
<artifactId>mysql-connector-java-5.1.24-bin</artifactId>
<version>5.1.24</version>
<scope>system</scope>
<systemPath>${basedir}/lib/mysql-connector-java-5.1.24-bin.jar</systemPath>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.1</version>
<configuration>
<source>1.7</source>
<target>1.7</target>
</configuration>
</plugin>
<!-- WHAT SHOULD I USE HERE? -->
</plugins>
</build>
How to solve this problem?

There is a maven plugin Apache Maven Shade Plugin that will build an uber jar for you

Add the Maven Assembly plugin with the descriptor jar-with-dependencies:
<build>
<plugins>
<plugin>
<artifactId>maven-assembly-plugin</artifactId>
<configuration>
<descriptorRefs>
<descriptorRef>jar-with-dependencies</descriptorRef>
</descriptorRefs>
<archive>
<manifest>
<mainClass>com.pany.your.MainClass</mainClass>
</manifest>
</archive>
</configuration>
<executions>
<execution>
<id>make-assembly</id>
<phase>package</phase>
<goals>
<goal>single</goal>
</goals>
</execution>
</executions>
</plugin>
Note that this doesn't add the JAR; instead it unpacks all JARs which are listed as dependencies and adds their content to the resulting JAR (so you'll see all the class files from the MySQL JAR in the result instead of the MySQL JAR itself).
EDIT There is a caveat, though: Maven ignores JARs with scope=system for many operations. See also: How to include external jars in maven jar build process?
If Maven doesn't add the JAR to the output, then you must install all JARs with this scope into your local maven repo ($HOME/.m2/repository) using the mvn install:file-install command. See http://maven.apache.org/plugins/maven-install-plugin/usage.html how to do that.
Note: Installing libraries in your local repo is the preferred way; you should really consider it. For one, the scope=system will no longer confuse you (since many plugins handle them in a special way). Plus you need to do this only once. Afterwards, you can use this library in many Maven projects.
Before installing, you should check http://search.maven.org/ to see if the dependency isn't already known to Maven.
MySQL is: http://search.maven.org/#artifactdetails%7Cmysql%7Cmysql-connector-java%7C5.1.32%7Cjar

How to run a plugin only for "war" package type in Maven?

Provided two Maven projects: J (jar), W (war); both depend on one parent P (pom). The parent has a plugin, which must only run for the project "W".
How does one go about doing this:
without creating separate parent projects
without using a profile (so build must still be executed with mvn clean package)
J (jar)
<project>
<parent>
<artifactId>P</artifactId>
</parent>
<artifactId>J</artifactId>
<packaging>jar</packaging>
</project>
W (war)
<project>
<parent>
<artifactId>P</artifactId>
</parent>
<artifactId>W</artifactId>
<packaging>war</packaging>
</project>
P (pom)
<project>
<artifactId>P</artifactId>
<packaging>pom</packaging>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<executions>
<execution>
<phase>package</phase>
<goals>
<goal>jar</goal>
</goals>
<configuration>
<classifier>classes</classifier>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>
</project>

I think you can achieve this using Profile Activation. Ideally, the activation condition would be something like "packaging type is war", but apparently, this condition cannot be implemented in Maven. However, in your case, there is a condition that can be implemented and that is probably equivalent in practice: "there is a src/main/webapp directory".
This is how your pom.xml might look like:
<profiles>
<profile>
<activation>
<file>
<exists>src/main/webapp</exists>
</file>
</activation>
<build>
[plugin configuration]
</build>
</profile>
</profiles>

One way to do this would be to place the plugin in the parent pom within <pluginManagement> section. Thereafter specify the plugin in the project(s) that you want it to run.
In your case, you would specify the plugin for project J and not W.
P
<build>
...
<pluginManagement>
<plugins>
<plugin>
<groupId>...</groupId>
<artifactId>...</artifactId>
... other plugin details ...
</plugin>
</plugins>
</pluginManagement>
...
</build>
J
<build>
...
<plugins>
<plugin>
<groupId>...</groupId>
<artifactId>...</artifactId>
<plugin>
</plugins>
...
</build>

Short answer: Maven doesn't appear to have a good way to do what you're trying to do. I've spent a fair amount of time trying to solve a similar problem and haven't found anything satisfactory.
You've already discovered two of the possible solutions: introduction of an additional parent pom for the wars (perhaps the additional pom extends the original parent so you don't have to duplicate all of its config), or duplicating the jar plugin config in all of the war poms. As you've said, neither of these is ideal.
Another possibility is to use the maven-assembly-plugin instead of the jar plugin to build the classified jar for the war projects. The assembly plugin is not included in the default lifecycles for either jar or war packaging, so you could configure it in the parent's <pluginManagement> section and then only reference it in the war projects as Raghuram described. If you need a custom assembly descriptor you will probably want to follow the sharing the assembly descriptors example.