Serving binaries from a controller

[davidnewcomb]

I am trying to output jpegs from a database to the browser, but I don't know what to return from the handleRequest.
I've set the contentType and filled up the response, but when I return null I get a NPE.

Is this the right method for serving binaries? If so what am I supposed to return.

public class GetImageController implements Controller
  {
  
  private ClipCache clipcache ;
  
  /** Logger for this class and subclasses */
  protected final Log logger = LogFactory.getLog (getClass ()) ;

  public ModelAndView handleRequest (HttpServletRequest request, HttpServletResponse response)
      throws Exception
    {
    String clipIdStr = StringUtils.clean (request.getParameter ("cid")) ;
    if (clipIdStr == null)
      return null ;
    String zoneIdStr = StringUtils.clean (request.getParameter ("zid")) ;
    if (zoneIdStr == null)
      return null ;
    
    int zid = StringUtils.toInt ("zoneid", zoneIdStr) ;
    int cid = StringUtils.toInt ("clipid", clipIdStr) ;

    logger.info ("Requested clip is zoneid=" + zid + " clipid=" + cid) ;

    Clip clip = clipcache.get (zid, cid) ;
    ClipThumbnail ct = clip.getClipThumbnail() ;
    
    response.setContentType (ct.getMimeType ()) ;
    OutputStream os = response.getOutputStream () ;
    InputStream fin = ct.getContent () ;
    
    byte[] buf = new byte[4096] ;
    int count = 0 ;
    while (true)
      {
      int n = fin.read (buf) ;
      if (n == -1)
        {
        break ;
        }
      count = count + n ;
      os.write (buf, 0, n) ;
      }
    os.flush () ;
    os.close () ;
    fin.close () ;
    
    return null ;
    }
  
  }

[sandstorm]

but when I return null ...

What do you mean by this ?

If you mean this:

if (zoneIdStr == null)
      return null ;

Then u have coded the following semantics:

"If the parameters supplied are null, which is a logical error/invalid argument, then report to the Controller client that you are having processed the request manually, so that it (the client - in this case the controller servlet) not to bother resolving the views"

In any case what do you mean by "when", like in "when I return null" ?
Can u post some error messages ?

[davidnewcomb]

Thanks sandstorm,

If the parameters supplied are null, which is a logical error/invalid argument, then report to the Controller client that you are having processed the request manually, so that it (the client - in this case the controller servlet) not to bother resolving the views

really helped a lot.

As it turned out my thing was blowing up because there was a bad injection.

[sandstorm]

No problems ;]
I was thinking that too...
The problem I saw was not what u spoke of, so the problem lies elsewhere- the injection (possibly).

[davidnewcomb]

If I want to say that the document they are looking for is not available at the moment (404 or similar) how can i do that? This error message would be different to an invalid parameter message.

[Marten Deinum]

response.sendError(HttpServletResponse.SC_NOT_FOUND, "Some message indicating that something was missing");

The above should do that. You could ommit the message and use the sendError with the error code only.

Or you can throw some specific Exception and configure an HandlerExceptionResolver.