Add those lines to your web.xml:
  <!-- GisViewer Servlets -->
  <servlet>
    <servlet-name>GisViewerService</servlet-name>
    <servlet-class>org.gcube.portlets.user.gcubegisviewer.server.GCubeGisViewerServletImpl</servlet-class>
  </servlet>
  
  <servlet-mapping>
    <servlet-name>GisViewerService</servlet-name>
    <url-pattern>/<YOUR APPLICATION NAME>/GisViewerService</url-pattern>
  </servlet-mapping>
  
  <!-- Workspace Light Tree servlet -->
  <servlet>
    <servlet-name>WorkspaceLightService</servlet-name>
    <servlet-class>org.gcube.portlets.user.workspace.lighttree.server.WorkspaceServiceImpl</servlet-class>
  </servlet>

  <servlet-mapping>
    <servlet-name>WorkspaceLightService</servlet-name>
    <url-pattern>/<YOUR APPLICATION NAME>/WorkspaceLightService</url-pattern>
  </servlet-mapping>