How do I return status 404 from doView in Liferay/Java

One of our developers wrote a portlet that uses the doView method to render relevant content. However, we are receiving NPE's if the user goes to a page under a valid route of that portlet with no valid record.

An example is:

/<location>/<postcode>/<propertyname>

/london/w1/10-downing-street - VALID

/london/w1/sdsd-downing-streetsss - INVALID

The slug will pull the record from the db as it's unique but if it's invalid it throws an NPE on fillRenderRequestAttributes and we need it to throw a status 404.

Code

public void doView(RenderRequest renderRequest, RenderResponse renderResponse) throws IOException, PortletException {

    fillRenderRequestAttributes(renderRequest, renderResponse);
    
    if(_log.isDebugEnabled())
    {
       _log.debug("DoView");
    }
    try
    {
       super.doView(renderRequest, renderResponse);
    }
    catch(Exception e)
    {
       _log.debug("Broken");
       e.printStackTrace();
    }
    
}

I assume we need a try/catch around fillRenderRequestAttributes and in the catch we need to throw a 404? How can this be done? Any examples would be helpful.

doView is rendering a portlet's output, not a full page. Thus, it doesn't have a status code. The page is rendered elsewhere (e.g. decorated with the theme, and with any number of other portlets on the page that might still show relevant content).

In the portlet world you're not dealing with HttpServletRequest/Response pairs, but with PortletRequest/Response pairs (as seen here in the incarnation of RenderRequest/Response). Thinking in HTTP return codes is wrong: You can't even guarantee that the portlet is rendered before the response is already sent back to the browser: Once you determine that your portlet can't render appropriate output, the page might already be on its way, with status code 200. Or it might be rendered asynchronously and just injected into a page.

If the portlet can't render appropriate output in doView, you'll need to catch the exception and display a proper error message in the portlet.

Otherwise, consider implementing serveResource, where you have more control, or a REST endpoint. But note: 404 is a technical error, while you're handling a business layer error - both should be handled differently.