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maven: Some input files use unchecked or unsafe operations [duplicate]

In NetBeans 7.2, I'm having trouble finding how to compile using -Xlint:unchecked in a Maven project. Under an Ant project, you can change compiler flags by going to Project Properties -> Compiling, but Maven projects don't seem to have any such option.
Is there any way to configure the IDE to compile with such flags using Maven?

I guess you can set compiler arguments in your pom.xml. Please refer this http://maven.apache.org/plugins/maven-compiler-plugin/examples/pass-compiler-arguments.html
<compilerArgument>-Xlint:unchecked</compilerArgument>

I want to elaborate on #Nishant's answer. The compilerArgument tag needs to go inside plugin/configuration tag. Here is a full example:
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.3</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
<testSource>1.8</testSource>
<testTarget>1.8</testTarget>
<compilerArgument>-Xlint:unchecked</compilerArgument>
</configuration>
</plugin>
</plugins>

This works for me...
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.8.1</version>
<configuration>
<source>11</source>
<target>11</target>
<compilerArguments>
<endorseddirs>${endorsed.dir}</endorseddirs>
</compilerArguments>
<compilerArgs>
<arg>-Xlint:unchecked</arg> <-------this right here ---->
</compilerArgs>
</configuration>
</plugin>
</plugins>

The pom file information is spot on. I had the additional challenge of building someone else's Maven project in Jenkins and not having access to the pom file repository.
I created a pre-build step to insert the compiler parameter into the pom file after downloading it from git, for example
sed -i 's|/target> *$|/target>\n<compilerArgument>\n-Xlint:deprecation\n</compilerArgument>|' $WORKSPACE/pom.xml

No main manifest attribute error when running jar

I have create a maven project. It is running fine. Now i want to run my code through jar. After maven build i got a jar file in .m2 folder. When I try to run this jar using
java -jar "jar path"
getting no main manifest attribute, in "jar path".
My POM.xml is
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.3</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
</configuration>
</plugin>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>exec-maven-plugin</artifactId>
<version>1.2.1</version>
<configuration>
<mainClass>main.Application</mainClass>
</configuration>
</plugin>
</plugins>
</build>
Please suggest how to get over rid of the problem.

Now i want to run my code through jar
exec-maven-plugin is for executing a program during a maven build.
You don't want it.
And as a side note, you don't have specified any goal for it.
So, it will do nothing.
You want to package your jar in a way that it is executable.
So use rather the maven-jar-plugin :
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<configuration>
<archive>
<manifest>
<mainClass>main.Application</mainClass>
</manifest>
</archive>
</configuration>
</plugin>
To create a JAR with dependencies specified in the pom, instead of, use the maven-assembly-plugin with the jar-with-dependencies descriptorRef:
<build>
<plugins>
<plugin>
<artifactId>maven-assembly-plugin</artifactId>
<configuration>
<archive>
<manifest>
<mainClass>main.Application</mainClass>
</manifest>
</archive>
<descriptorRefs>
<descriptorRef>jar-with-dependencies</descriptorRef>
</descriptorRefs>
</configuration>
</plugin>
</plugins>
</build>

scala maven plugin not packaging scala files into jar

I'm new to maven and currently try to assemble a scala project with it. Project structure:
dir
|
|--src/main/java
|
|--src/main/scala
|
|--pom.xml
I was kind of surprised that classes compiled from *.java end up in jar, but one compiled from *.scala do not. I added these plugins to pom.xml
<plugins>
<plugin>
<groupId>net.alchim31.maven</groupId>
<artifactId>scala-maven-plugin</artifactId>
<version>3.1.3</version>
</plugin>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<source>1.8</source>
<target>1.8</target>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<version>2.4</version>
<configuration>
<archive>
<manifest>
<addClasspath>true</addClasspath>
<classpathPrefix>lib/</classpathPrefix>
<mainClass>HelloWorld</mainClass>
</manifest>
</archive>
</configuration>
</plugin>
</plugins>
I though maven-jar-plugin is responsible for assembling jar files. But for some reason, it does not add scala-compiled classes.
QUESTION: Who adds .class file into a final jar after executing mvn install? How to add .class-files compiled with scala compiler?

mvn package will build your jar, however maven-compiler-plugin will only compile your java source files not your scala source files. Scala-maven-plugin can be used to compile both java and scala sources.
I wrote a blog post on this a while ago, that may help http://blog.rizvn.com/2016/04/scala-and-maven.html
You will need to tell maven about src/main/scala, since you are putting your scala code under src/main/java. This is done through the build section like so:
<build>
<sourceDirectory>src/main/scala</sourceDirectory>
<testSourceDirectory>src/test/scala</testSourceDirectory>
...
</build>

Can you try something like this, using "scala-maven-plugin" instead. Then execute maven goal : mvn clean package
<build>
<sourceDirectory>${basedir}/src</sourceDirectory>
<resources>
<resource>
<directory>${basedir}/src/test/resources</directory>
</resource>
</resources>
<plugins>
<plugin>
<groupId>net.alchim31.maven</groupId>
<artifactId>scala-maven-plugin</artifactId>
<version>${scala-maven-plugin.version}</version>
<configuration>
<sourceDir>${basedir}/src</sourceDir>
<outputDir>${basedir}/target/classes</outputDir>
</configuration>
<executions>
<execution>
<id>scala-compile-first</id>
<phase>process-resources</phase>
<goals>
<goal>compile</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>

Eclipse deletes files under WEB-INF on every run

I'm trying to setup Maven with my GWT project but every time that I start debugging, it deletes web.xml and other files that are required to start.
Code fragment related to build from my pom.xml :
<build>
<outputDirectory>${webappDirectory}/WEB-INF/classes</outputDirectory>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>${maven-compiler-plugin.version}</version>
<configuration>
<webXml>${webappDirectory}/WEB-INF/web.xml</webXml>
<source>${target.jdk}</source>
<target>${target.jdk}</target>
<encoding>${project.build.sourceEncoding}</encoding>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-war-plugin</artifactId>
<version>${maven-war-plugin.version}</version>
<configuration>
<failOnMissingWebXml>false</failOnMissingWebXml>
<archiveClasses>true</archiveClasses>
</configuration>
</plugin>
</plugins>
</build>

No classes in war maven

I'm pretty new in using og maven, an I got stuck. mvn clean install does not generate classes :(
I'm using the following code in my pom :
<plugin>
<artifactId>maven-war-plugin</artifactId>
<version>2.4</version>
<configuration>
<webXml>WebContent\WEB-INF\web.xml</webXml>
<archiveClasses>true</archiveClasses>
</configuration>
</plugin>

Please read the usage page first, it will show the expected folder structure.
So java sources are expected in src/main/java.
BTW: If you still want to use WebContent, set the warSourceDirectory to WebContent, remove all other configuration.

<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<source>1.6</source>
<target>1.6</target>
<optimize>true</optimize>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-war-plugin</artifactId>
<configuration>
<webResources>
<resource>
<directory>src/main/webapp</directory>
<filtering>true</filtering>
</resource>
</webResources>
</configuration>
</plugin>
</plugins>