settings.xml for maven 3.8.1

I switched from Netbeans to Eclipse IDE for Java applications and remote debugging. The Maven project wizard generated a java project with the pom.xml and build.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>IntelligentHome</groupId>
  <artifactId>RaspberryPi</artifactId>
  <version>0.0.1-SNAPSHOT</version>

  <name>RaspberryPi</name>
  <!-- FIXME change it to the project's website -->
  <url>http://www.example.com</url>

<!--
    <build>
      <plugins>
         <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-jar-plugin</artifactId>
            <configuration>
               <archive>
                  <manifest>
                     <mainClass>IntelligentHome.RaspberryPi.App</mainClass>
                  </manifest>
               </archive>
            </configuration>
         </plugin>
      </plugins>
   </build>
-->

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.source>1.7</maven.compiler.source>
    <maven.compiler.target>1.7</maven.compiler.target>
  </properties>

  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.12</version>
      <scope>test</scope>
    </dependency>
  </dependencies>

<pluginRepositories>
   <pluginRepository> 
    <id>maven2</id> 
    <url>https://repo.maven.apache.org/maven2/</url> 
  </pluginRepository> 
</pluginRepositories>

  <build>
    <pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
      <plugins>
        <!-- clean lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#clean_Lifecycle -->
        <plugin>
          <artifactId>maven-clean-plugin</artifactId>
          <version>3.1.0</version>
        </plugin>
        <!-- default lifecycle, jar packaging: see https://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_jar_packaging -->
        <plugin>
          <artifactId>maven-resources-plugin</artifactId>
          <version>3.0.2</version>
        </plugin>
        <plugin>
          <artifactId>maven-compiler-plugin</artifactId>
          <version>3.8.0</version>
        </plugin>
        <plugin>
          <artifactId>maven-surefire-plugin</artifactId>
          <version>2.22.1</version>
        </plugin>
        <plugin>
          <artifactId>maven-jar-plugin</artifactId>
          <version>3.0.2</version>
        </plugin>
        <plugin>
          <artifactId>maven-install-plugin</artifactId>
          <version>2.5.2</version>
        </plugin>
        <plugin>
          <artifactId>maven-deploy-plugin</artifactId>
          <version>2.8.2</version>
        </plugin>
        <!-- site lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#site_Lifecycle -->
        <plugin>
          <artifactId>maven-site-plugin</artifactId>
          <version>3.7.1</version>
        </plugin>
        <plugin>
          <artifactId>maven-project-info-reports-plugin</artifactId>
          <version>3.0.0</version>
        </plugin>
      </plugins>
    </pluginManagement>
  </build>
</project>

Executing the file using ANT build results in this Error

[artifact:mvn] [INFO] Error resolving version for 'org.apache.maven.plugins:maven-resources-plugin': Plugin requires Maven version 3.0

executing

mvn -version Apache Maven 3.6.3

list the current maven version. This version is also linked in the preferences of maven inside the IDE

Some research reveals that maven2 is no longer maintained and should not be used. For some reason the folder ./m2 is still in my home drive and used as user settings for the maven build

the settings.xml that is apparently used reads

 <settings xmlns="https://maven.apache.org/SETTINGS/1.0.0"
      xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance"
      xsi:schemaLocation="https://maven.apache.org/SETTINGS/1.0.0
                          https://maven.apache.org/xsd/settings-1.0.0.xsd">
      <localRepository/>
      <interactiveMode/>
      <offline/>
      <pluginGroups/>
      <servers/>
      <mirrors>
        <mirror>
          <id>centralhttps</id>
          <mirrorOf>central</mirrorOf>
          <name>Maven central https</name>
          <url>http://insecure.repo1.maven.org/maven2/</url>
        </mirror>
      </mirrors>
      <proxies/>
      <profiles/>
      <activeProfiles/>
   </settings>

a line linking something to maven2.

How do I change the settings.xml to the current maven version? How does Eclipse changes the settings.xml when maven is upgraded?

When I remove all the plugins no errors are thrown and the .jar is executed on the target. This leads to another question: What do this plugins do when the program works fine without them?

The folder $HOME/.m2 is used for both maven2 and maven3. How confusing? :-) Unless you are doing something special, you can simply remove your settings.xml file.

Although you didn't ask, unless you have a specific need for Eclipse, I recommend IntelliJ community edition. Eclipse has to import the pom.xml into its own configuration. Netbeans and IntelliJ both work with mvn without this step. There is also a special maven plugin for Eclipse that you may want to use if you continue with Eclipse.

<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-eclipse-plugin</artifactId>

That being said, I haven't touched Eclipse for a couple of years...