[TAP5-901] Generics return wrong type when subclassing page

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 5.1.0.4
• Fix Version/s: 5.4
• Labels: generics patch
• Assignee: Unassigned
• Reporter: Mike Leonardo
• Created: 20/Oct/09 18:33
• Updated: 20/Aug/14 10:36
• Resolved: 20/Aug/14 08:25

Description

I have a custom library that has the following classes:

{{{
public abstract class AbstractViewPage<T extends StaticPage<T, V>, V extends StaticPageVersion> {
private static final Pattern ID = Pattern.compile("^
d+$");

@InjectDao(StaticPage.class) private Dao<T> dao;
@Inject private Response response;

private T page;

void onActivate(String key) throws IOException {
if (ID.matcher(key).matches())
page = dao.get(Long.parseLong(key));
else

{ page = dao.get(eq("name", key)); }

if (page != null && page.getLive() == null)
page = null;

if (page == null)
response.sendError(404, "Page not found");
}

public T getPage()

{ return page; }

public void setPage(T page)

{ this.page = page; }

/** Returns the versioned content to display. */
public V getContent()

{ if (page == null) return null; return page.getLive(); }

}
}}}

{{{
/** Displays a static page */
@Public
public class Page extends AbstractViewPage<IFPStaticPage, IFPStaticPageVersion> {

@Inject private IAuth auth;
@Inject private HttpServletRequest request;
@Inject private HttpServletResponse response;

Object onActivate()

{ IFPStaticPage page = getPage(); if (page != null && page.isRestricted() && auth.getAccount(request, response) == null) return "start"; return null; }

public boolean isTopLevel()

{ return getPage() == getPage().getSectionPage(); }

void onEndElementFromBreadcrumb(Element e)

{ if ("a".equals(e.getName())) e.getContainer().raw("  ›  "); }

}
}}}

As you can see, based on generics the method "getContent" should return a IFPStaticPageVersion.
This works fine when I use this Page.class directly.

Recently I wanted to extend this Page.class to add a few features specific to one project. When I extended this class (no template so that it would use the Page.class template) I ended up getting an error on the subclass. The error occurred because getContent returned a completely different class instead of IFPStaticPageVersion.

I work around I found to fix this is to override the getContent method so that it explicitly defines the return type. But I had to do this in both Page.class and the subclass (Page2.class). Here's my addition to both classes:

{{{

@Override
public IFPStaticPageVersion getContent()

{ return super.getContent(); }

}}}

Obviously I shouldn't have to do this to get the correct class back (especially not to both Page.class AND Page2.class.