Why I can't get source code an documentation by using maven

I'm got RXTX library in Java Maven project in Eclipse by adding dependency in pom.xml:

<dependency>
    <groupId>org.rxtx</groupId>
    <artifactId>rxtx</artifactId>
    <version>2.1.7</version>
</dependency>   

But how to ask maven to download documentation and source code for it?

I have settings in project properties that should help me with that, but I don't see any documents and sources.

I have plugin that I hope will help me to download source code:

            <plugin>
                <artifactId>maven-source-plugin</artifactId>
                <version>2.2.1</version>
                <executions>
                    <execution>
                        <id>attach-sources</id>
                        <phase>verify</phase>
                        <goals>
                            <goal>jar-no-fork</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>

But after execution mvn verify I found that source and doc are not available:

m2e-lastUpdated.properties
11/07/2018  07:03 PM                 0 rxtx-2.1.7-javadoc.jar-not-available
11/07/2018  07:03 PM               255 rxtx-2.1.7-javadoc.jar.lastUpdated
11/07/2018  07:03 PM                 0 rxtx-2.1.7-sources.jar-not-available
11/07/2018  07:03 PM               255 rxtx-2.1.7-sources.jar.lastUpdated
11/05/2018  12:33 PM            59,464 rxtx-2.1.7.jar
11/05/2018  12:33 PM               126 rxtx-2.1.7.jar.sha1
11/05/2018  12:33 PM               841 rxtx-2.1.7.pom
11/05/2018  12:33 PM               126 rxtx-2.1.7.pom.sha1
11/05/2018  12:33 PM               192 _remote.repositories

What else I can do to get RXTX library source code?

You are correct, it seems the Maven repository doesn't contain the source code for RXTX.

You can find the source code for RXTX on GitHub.