<?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>

    <!-- Information !-->
    <groupId>com.crashitor</groupId>
    <artifactId>Crashitor</artifactId>
    <packaging>jar</packaging>
    <version>1.0</version>

    <!-- Compiler settings !-->
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>12</maven.compiler.source>   <!-- JDK 12 !-->
        <maven.compiler.target>12</maven.compiler.target>   <!-- JDK 12 !-->
    </properties>

    <!-- External Jars !-->
    <dependencies>
        <!-- JTattoo.jar !-->
        <dependency>
            <groupId>com.jtattoo</groupId>
            <artifactId>JTattoo</artifactId>
            <version>1.6.1</version>
            <scope>system</scope>
            <systemPath>${basedir}/src/main/resources/JTattoo-1.6.11.jar</systemPath>
        </dependency>

        <!-- javax.json !-->
        <dependency>
            <groupId>org.glassfish</groupId>
            <artifactId>javax.json</artifactId>
            <version>1.1.4</version>
            <scope>system</scope>
            <systemPath>${basedir}/src/main/resources/javax.json-1.1.4.jar</systemPath>
        </dependency>
    </dependencies>

    <!-- Build settings !-->
    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-jar-plugin</artifactId>
                <version>2.4</version>
                <configuration>
                    <archive>
                        <manifest>
                            <mainClass>com.crashitor.Core</mainClass>
                        </manifest>
                    </archive>
                </configuration>
            </plugin>

            <!-- Compiler !-->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.6.2</version>
                <configuration>
                    <release>12</release>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

mvn clean package
java -jar target/Crashitor-1.0.jar

output: Exception in thread "AWT-EventQueue-0" java.lang.NoClassDefFoundError: javax/json/Json