How to add anchor in Wicket's setResponsePage(

Question

We need to redirect users that access a certain url to a Wicket page and scroll to a anchor in the page. E.g., the users link directly to http://.../target/url/123. Afterwards, the 123 id is looked up from database. Subsequently, the user will be redirected to a different page based on if the entity was found or not.

After the entity has been fetched the user should be redirected to http://.../another/url/123#element123. How can we achieve this with Wicket? The page should also be accessible without the anchor, and preferably, the solution should be generic.

One solution I came up with is to override the PageParametersEncoder logic to append #anchor to url when the PageParameters contains an entry named anchor. However, this means that I also need to extend the Url class with my own to append the anchor.

public class ExtendedEncoder extends PageParametersEncoder {

    public static final String ANCHOR = "anchor";

    @Override
    public Url encodePageParameters(PageParameters pageParameters) {
        Url fromSuper = super.encodePageParameters(pageParameters.remove(ANCHOR));
        return new ExtendedUrl(fromSuper,
                pageParameters.get(ANCHOR).toOptionalString());

    }
}

public class ExtendedUrl extends Url {
        private String anchor;

        private ExtendedUrl(Url url, String anchor) {
            super(url);
            this.anchor = anchor;
        }

        @Override
        public String toString(StringMode mode, Charset charset) {
            return super.toString(mode, charset)
                   + anchor == null ? "" : "#" + anchor;
        }
    }
}

Are there any other solutions for the problem?

Answer 1

The following code renders a javascript snippet into the html of your target page that upon page load will focus the page on the anchor specified in the url.

@Override
public void renderHead(IHeaderResponse response) {
    super.renderHead(response);
    long anchor = getRequest().getQueryParameters().getParameterValue("anchor").toLong(0);
    if (anchor > 0) {
        response.render(new OnLoadHeaderItem("location.href='#anchor" + anchor + "';"));
        anchor = 0;
    }
}

btw, this is for wicket 6. You can do similar stuff though in 1.5 and previous versions.

Answer 2

you could ask for the URL of the page and then redirect

String fullUrl = RequestCycle.get().getUrlRenderer()
    .renderFullUrl(Url.parse((String) urlFor(RedirectPage.class,parameters)));
setResponsePage(new RedirectPage(fullUrl+"#anchor"));