import org.apache.cxf.frontend.ServerFactoryBean;
import org.apache.cxf.jaxrs.swagger.Swagger2Feature;
...

    Swagger2Feature feature = new Swagger2Feature();

    // customize some of the properties
    feature.setBasePath("/api");
    	
   	// add this feature to the endpoint (e.g., to ServerFactoryBean's features) 
   	ServerFactoryBean sfb = new ServerFactoryBean();
   	sfb.getFeatures().add(feature);

<web-app>
    <context-param>
        <param-name>contextParam</param-name>
        <param-value>contextParamValue</param-value>
    </context-param>
    <servlet>
        <servlet-name>CXFServlet</servlet-name>
        <display-name>CXF Servlet</display-name>
        <servlet-class>
              org.apache.cxf.jaxrs.servlet.CXFNonSpringJaxrsServlet
        </servlet-class>
        <init-param>
            <param-name>jaxrs.serviceClasses</param-name>
            <param-value>
                           org.apache.cxf.systest.jaxrs.BookStore
            </param-value>
        </init-param>
        <init-param>
            <param-name>jaxrs.features</param-name>
            <param-value>
                        org.apache.cxf.jaxrs.swagger.Swagger2Feature
                        (basePath=/somepath)
            </param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>
    
    <servlet-mapping>
        <servlet-name>CXFServlet</servlet-name>
        <url-pattern>/*</url-pattern>
    </servlet-mapping>
    
</web-app>