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Override version of Maven plugin used in parent pom to new version in main pom

Working on multi-module maven project. Have maven-compiler-plugin used in parent pom as follows:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>2.3.2</version>
<configuration>
<source>${java.version}</source>
<target>${java.version}</target>
</configuration>
</plugin>
Want to use <version>3.1</version> in the main project pom due to its incremental compile support. Do not have write access in parent pom. How can i just configure plugin in main project pom to use new version?

You can override the plugin in submodule
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.1</version>
<configuration>
<source>${java.version}</source>
<target>${java.version}</target>
</configuration>
</plugin>

Execute a Maven plugin with --enable-preview in POM

I have a custom Maven plugin which makes use of JDK 12 preview features. I compile the plugin setting --enable-preview as compiler arg, i.e.
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<compilerArgs>
<compilerArg>--enable-preview</compilerArg>
</compilerArgs>
</configuration>
</plugin>
When I want to execute the plugin, I add the plugin like this in the POM:
<plugin>
<groupId>my.group</groupId>
<artifactId>my-plugin</artifactId>
<executions>
<execution>
<phase>generate-sources</phase>
<goals>
<goal>my-goal</goal>
</goals>
</execution>
</executions>
</plugin>
But this fails with:
Preview features are not enabled for MyPluginMojo. Try running with '--enable-preview'
How can I enable preview features in a plugin execution?

For me, I had to add a config file to my build directory at:
.mvn/jvm.config
containing:
--enable-preview
This will make sure that Maven passes the correct parameters to JVM

You made a mistake in your pom. <compilerArgs> takes nested <arg>, like so:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.8.1</version>
<configuration>
<source>17</source>
<target>17</target>
<compilerArgs>
<arg>--enable-preview</arg>
</compilerArgs>
</configuration>
</plugin>

For JDK 17, this works for me:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<source>17</source>
<target>17</target>
<compilerArgs>--enable-preview</compilerArgs>
</configuration>
</plugin>

Possible to target specific TestNG.xml files via Maven POM File?

Possible to target only one of the two TestNG xml files listed within my Maven POM File?
My Maven POM file points to two xml files: uat.xml and preprod.xml, how do i target only one of the xml files using maven commands such as mvn clean compile test?
<build>
<pluginManagement>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.6.1</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
<fork>true</fork>
<!--<executable>C:\Program Files\Java\jdk1.8.0_121\bin\javac.exe</executable> -->
<executable>${env.JAVA_HOME}\bin\javac.exe</executable>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-surefire-plugin</artifactId>
<version>2.20</version>
<configuration>
<suiteXmlFiles>
<suiteXmlFile>uat.xml</suiteXmlFile>
<suiteXmlFile>preprod.xml</suiteXmlFile>
</suiteXmlFiles>
<testErrorIgnore>false</testErrorIgnore>
<testFailureIgnore>false</testFailureIgnore>
</configuration>
</plugin>
</plugins>
</pluginManagement>
</build>

See below. You will reference the file by name. So,
mvn clean test -Dtestfile=uat.xml
<configuration>
<suiteXmlFiles>
<suiteXmlFile>${testfile}</suiteXmlFile>
</suiteXmlFiles>
</configuration>

enabling the lambda expression

In the program like
entities.stream().filter(m->m.getId()==id).findAny().get();
where entities is a List. After setting all the libraries and other SDKs to Java 8. we are getting the error as:
use -source 8 or higher to enable lambda expressions

This is how solved my problem by adding the below plugin settings in my parent POM file.
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.1</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
</configuration>
</plugin>
</plugins>
</build>

How to create a new classes for each compilation using maven plugin

In case of my project I need to create new classes after each compilation. For compilation I'm using maven compiler plugin 3.1. I tried to use compilerReuseStrategy = alwaysNew option but it didn't make any affect, it always compile only changed classes. Here is plugin declaration in pom.xml:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.1</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
<compilerReuseStrategy>alwaysNew</compilerReuseStrategy>
</configuration>
</plugin>
An I doing something wrong or that's a bug and this option really doesn't work?

If you are talking about the incremental feature fo the maven-compiler-plugin you can change this behaviour by the following configuration:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.1</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
<useIncrementalCompilation>false</useIncrementalCompilation>
</configuration>
</plugin>
The compileReuseStrategy in contradiction is intended to define the behaviour in relationship with multi-threaded running of the compiler.

What about using mvn clean install?