During plugin development time, it's possible that you need dependencies to another plugin or a spécific API. It's necessary to add dependencies, plugins et APIs, in pom.xml file plugin.
Consider plugin need the Document plugin to work. It's necessary to add dependency following in pom.xml file :
...
<dependencies>
...
<dependency>
<groupId>fr.paris.lutece.plugins</groupId>
<artifactId>plugin-document</artifactId>
<version>1.9.0</version>
<type>lutece-plugin</type>
</dependency>
...
</dependencies>
...