adding a "outdated " maven dependency from different url (repository) - pom.xml

Question

let say we would like to add this maven dependency in our POM.xml file from http://maven.jahia.org/maven2/ to a exiting POM file. What are some good(industry) practices of adding com.sun(or tools) dependency super pom ? new to maven, example or short reasonings are appreciated.
<!-- https://mvnrepository.com/artifact/com.sun/tools -->
<dependency>
<groupId>com.sun</groupId>
<artifactId>tools</artifactId>
<version>1.5.0</version>
<scope>system</scope>
</dependency>
<!-- Note: (http://maven.jahia.org/maven2/) -->
The existing POM file 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">
<parent>
<groupId>com.example</groupId>
<artifactId>example</artifactId>
<version>1.0.0</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>example-common</artifactId>
<packaging>jar</packaging>
<description>example</description>
<properties>
<example-version>7.2.0</example-version>
</properties>
<dependencies>
<dependency>
<groupId>com.example</groupId>
<artifactId>example-sdk</artifactId>
<version>${example-version}</version>
</dependency>
<dependencies>
</project>

Answer 1

This is a bit of an old question, but I had the same issue, and this worked.
Add into your project pom (also possible in maven settings if you need it for several projects), the Jahia repo.
<project>
...
<repositories>
<repository>
<id>jahia</id>
<name>jahia</name>
<url>http://maven.jahia.org/maven2/</url>
</repository>
</repositories>
...
</project>
If it's in the maven settings, then you put it inside of a profile but need to activate the profile when running maven (-Pprofilename) or via activation by default in settings.xml:
<profile>
...
<activation>
<activeByDefault>true
...
</profile>