ServiceManager.getService for ProjectService creation gives null value

I have written a ProjectService class as below:

public static class ProjectService {
    private HorBugTable bugsTable;

    public HorBugTable getHoBugTable() {
        return bugsTable;
    }

    void setHorBugTable(HorBugTable bugsTable) {
        this.bugsTable = bugsTable;
    }
}

I registered the class in XML the following way:

<extensions defaultExtensionNs="com.intellij">
    <toolWindow id="Video" secondary="false" icon="/icons/video6x16.svg" anchor="bottom"
                factoryClass="factory.DebuggerFactory"/>

    <projectService serviceInterface="factory.DebuggerFactory.ProjectService"
                    serviceImplementation="factory.DebuggerFactory.ProjectService" />
</extensions>

I get a null pointer exception when I instantiate this class with the following (I also see getService is depreciated but ComponentManager.getServices() shows compile error.) What am I doing wrong?

ProjectService projectService =  ServiceManager.getService(project, ProjectService.class);
projectService.setHorBugTable(bugsTable);