Sling Models request object

Hi All,

I want to use the SlingHttpServletRequest request object in another sling model.

For ex.-

@Getter
@Model(adaptables = {Resource.class,SlingHttpServletRequest.class}, adapters = Header.class,
        defaultInjectionStrategy = DefaultInjectionStrategy.OPTIONAL)
public class Header{
    @SlingObject
    Resource componentResource;
    @SlingObject
    SlingHttpServletRequest servletrequest;
    @ValueMapValue
    private String fileLarge;
    @ChildResource(name = "b2cnavigationItem")
    private List<navigation> b2cnavigationItem;
}


@Model(adaptables = {Resource.class,SlingHttpServletRequest.class}, adapters = navigation.class,
        defaultInjectionStrategy = DefaultInjectionStrategy.OPTIONAL)
public class navigation{
    @SlingObject
    Resource resource;
    @OSGiService
    SlingHttpServletRequest request;
    @ValueMapValue
    String domain;
    @Getter
    @ValueMapValue
    private String navigationText;
    @Getter
    @ValueMapValue
    private String navigationLink;
    @ValueMapValue
    private String expFragPath;
}

Above is the code, Now  I want to use the request object in "navigation" class. but I am getting Null.

However, I am getting request object in Header Class. but not getting in navigation class.

Can anyone help me here? I want to append the Request Url host in the expFragPath variable.