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The POM for org.apache.maven.plugins:maven-compiler-plugin:jar:3.8.6 is missing - not sure why

I have the following code.
I am trying to create a 'pom.xml' file for a bukkit plugin (Minecraft) using Maven.
However, this gives me the error: 'The POM for org.apache.maven.plugins:maven-compiler-plugin:jar:3.8.6 is missing'.
I have tried to trouble shoot a few different solutions but haven't been successful in any.
I would be so grateful for a helping hand!
<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>
<groupId>newestfile.here</groupId>
<artifactId>newestplugin</artifactId>
<version>0.0.1-SNAPSHOT</version>
<build>
<pluginManagement>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.8.6</version>
<configuration>
<source>19</source>
<target>19</target>
</configuration>
</plugin>
</plugins>
</pluginManagement>

The source and target look wrong, are you sure they shouldn't be 1.8? That is the only number I see listed. Double check that and try running mvn compile and see if that didn't fix it.

I changed the version to 3.10.1 and the target to 17 as follows, and the code successfully ran:
<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>
<groupId>newestfile.here</groupId>
<artifactId>newestplugin</artifactId>
<version>0.0.1-SNAPSHOT</version>
<build>
<pluginManagement>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.10.1</version>
<configuration>
<source>17</source>
<target>17</target>
</configuration>
</plugin>
</plugins>
</pluginManagement>
</build>
<repositories>
<repository>
<id>spigot-repo</id>
<url>https://hub.spigotmc.org/nexus/content/repositories/public/</url>
</repository>
</repositories>
<dependencies>
<dependency>
<groupId>org.spigotmc</groupId>
<artifactId>spigot-api</artifactId>
<version>1.16.5-R0.1-SNAPSHOT</version><!--change this value depending on the version or use LATEST-->
<type>jar</type>
<scope>provided</scope>
</dependency>
</dependencies>
</project>
Thanks so much for all your help!

maven-compiler-plugin doesn't have 3.8.6 version. You need to choose some other version. Here is the available version list https://mvnrepository.com/artifact/org.apache.maven.plugins/maven-compiler-plugin.

Eclipse maven exception java.lang.ExceptionInInitializerError: Cannot access defaults field of Properties [in thread "Worker-27: Building"]

I have just updated eclipse to Version: 2022-06 (4.24.0), and have the next exception in problems view (in pom.xml file):
Exception java.lang.ExceptionInInitializerError: Cannot access defaults field of Properties [in thread "Worker-27: Building"]
The pom.xml file contains:
<?xml version="1.0"?>
<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<modelVersion>4.0.0</modelVersion>
<parent>
...
</parent>
<artifactId>xxxx</artifactId>
<packaging>war</packaging>
<properties>
<maven.compiler.target>1.8</maven.compiler.target>
<maven.compiler.source>1.8</maven.compiler.source>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
<dependencies>
...
</dependencies>
<repositories>
<repository>
...
</repository>
</repositories>
<build>
<finalName>xxxx</finalName>
<plugins>
<plugin>
<artifactId>maven-war-plugin</artifactId>
<configuration>
<webXml>WebContent\WEB-INF\web.xml</webXml>
<encoding>UTF-8</encoding>
</configuration>
</plugin>
</plugins>
</build>
</project>
No problems when generating maven artifactory.
Any idea how to avoid these error?

the solution is modify maven-war-plugin adding version 3.3.2:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-war-plugin</artifactId>
<version>3.3.2</version>
<configuration>
<webXml>WebContent\WEB-INF\web.xml</webXml>
<encoding>UTF-8</encoding>
</configuration>
</plugin>
thanks

How can I dockerize multi module Spring app?

I'm trying to dockerize my multi module application (i'm using hexagonal architecture with Port and Adapters pattern).
Here is the structure of my application:
App structure
My root pom looks in this way:
<?xml version="1.0" encoding="UTF-8"?>
4.0.0
<groupId>org.example</groupId>
<artifactId>Example project</artifactId>
<packaging>pom</packaging>
<version>1.0-SNAPSHOT</version>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<source>17</source>
<target>17</target>
</configuration>
</plugin>
</plugins>
</build>
<modules>
<module>domain</module>
<module>infrastructure</module>
<module>application</module>
<module>fwm-launcher</module>
</modules>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.6.5</version>
</parent>
<properties>
<maven.compiler.source>18</maven.compiler.source>
<maven.compiler.target>18</maven.compiler.target>
</properties>

Below blog talks all about it. jib-maven-plugin is the easiest option to dockerize your app
https://www.baeldung.com/jib-dockerizing

spring boot package does not exist error

I'm compiling my project with mvn clean package, and failed with package does not exist.
The detail command:
Get the jar file target/xxxx.jar by running mvn clean package in source project.
install this jar file by running mvn install:install-file -Dfile=lib/xxxx.jar -DgroupId=com.company -DartifactId=source-package-name -Dversion=1.0.0 -Dpackaging=jar
add code to target project, which will use some functions in source project
compile target project by running mvn clean package, and it just failed with package does not exist
here is the source 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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.company</groupId>
<artifactId>source-package-name</artifactId>
<version>1.0.0</version>
<packaging>jar</packaging>
<name>source-package-name</name>
<description>xxxx</description>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.5.3.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>1.8</java.version>
</properties>
<dependencies>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<executions>
<execution>
<goals>
<goal>repackage</goal>
</goals>
</execution>
</executions>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-surefire-plugin</artifactId>
<configuration>
<argLine>-Xmx6144m</argLine>
</configuration>
</plugin>
</plugins>
</build>
</project>
here is the target 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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.company</groupId>
<artifactId>target-package-name</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>war</packaging>
<name>target-package-name</name>
<url>http://maven.apache.org</url>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<jdk.version>1.7</jdk.version>
<smartv-common.version>0.3.5s</smartv-common.version>
<spring.version>3.0.5.RELEASE</spring.version>
</properties>
<dependencies>
</dependencies>
<build>
<resources>
<resource>
<directory>src/main/resources</directory>
<excludes>
<!-- Exclude those since they are copied from the profile folder for
the build -->
<exclude>system.properties</exclude>
</excludes>
<filtering>false</filtering>
</resource>
</resources>
<finalName>xxxxx</finalName>
<!-- Set a compiler level -->
<extensions>
<extension>
<groupId>kr.motd.maven</groupId>
<artifactId>os-maven-plugin</artifactId>
<version>1.4.1.Final</version>
</extension>
</extensions>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.1</version>
<configuration>
<source>${jdk.version}</source>
<target>${jdk.version}</target>
<encoding>UTF-8</encoding>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-war-plugin</artifactId>
<version>2.6</version>
<configuration>
<!-- http://maven.apache.org/plugins/maven-war-plugin/examples/adding-filtering-webresources.html
http://stackoverflow.com/questions/12729513/how-to-overwrite-files-in-the-war-file-during-maven-build -->
<webResources>
<!-- Resources from the activated profile folder -->
<resource>
<targetPath>WEB-INF/classes/</targetPath>
<includes>
<include>system.properties</include>
</includes>
</resource>
</webResources>
</configuration>
</plugin>
</plugins>
</build>
</project>

Ideally, you shouldn't use a Spring Boot application (something that's been repackaged) as a dependency. From the documentation:
Like a war file, a Spring Boot application is not intended to be used as a dependency. If your application contains classes that you want to share with other projects, the recommended approach is to move that code into a separate module. The separate module can then be depended upon by your application and other projects.
If the proposed solution isn't possible in your situation, the documentation goes on to describe an alternative:
If you cannot rearrange your code as recommended above, Spring Boot’s Maven and Gradle plugins must be configured to produce a separate artifact that is suitable for use as a dependency. The executable archive cannot be used as a dependency as the executable jar format packages application classes in BOOT-INF/classes. This means that they cannot be found when the executable jar is used as a dependency.
To produce the two artifacts, one that can be used as a dependency and one that is executable, a classifier must be specified. This classifier is applied to the name of the executable archive, leaving the default archive for use as dependency.
To configure a classifier of exec in Maven, the following configuration can be used:
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<configuration>
<classifier>exec</classifier>
</configuration>
</plugin>
</plugins>
</build>

Maven + Eclipse cannot build path

I have found this solution on stackoverflow. Warning - Build path specifies execution environment J2SE-1.4
I am getting almost the same problem but instead of 1-4 i am having 1-6. Unfortunately I don't really understand this configuration thing. It's new thing to me. I am trying second answer to get this working. I found this pom.xml in src under my project and it's xml looks like this:
<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>eu.jpereira.trainings.designpatterns.creational.singleton</groupId>
<artifactId>singleton</artifactId>
<version>1.0-SNAPSHOT</version>
<packaging>jar</packaging>
<name>singleton</name>
<url>http://maven.apache.org</url>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.9</version>
<scope>test</scope>
</dependency>
</dependencies>
<!-- Configure Build Process -->
<build>
<plugins>
<!-- Compiler plugin to use Java 1.6 compatiblity -->
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>2.3.2</version>
<configuration>
<source>1.6</source>
<target>1.6</target>
</configuration>
</plugin>
<!-- Eclipse plugin to force download of source and JavaDoc jars -->
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-eclipse-plugin</artifactId>
<version>2.8</version>
<configuration>
<wtpversion>2.0</wtpversion>
<downloadSources>true</downloadSources>
<downloadJavadocs>true</downloadJavadocs>
</configuration>
</plugin>
</plugins>
</build>
</project>
What and where should I add sth? I am using Eclipse on Windows 7. My version of java is: 1.8.0.25-b18 Words like plugin and Maven and JUnit are highlighted red. I would be grateful for help!

Try
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>2.3.2</version>
<configuration>
<source>1.4</source>
<target>1.4</target>
</configuration>
</plugin>
And then regenerate the Eclipse project with mvn eclipse:eclipse.