Redirect from HTTP filter does not work

[eclipse-rap]

Redirect from HTTP filter does not work

[mknauer]

Thanks, RAP 3.18, or to be more precise, RAP <3.21 reflects my theory, because with 3.21 M1 we changed the implementation from XHR to fetch in order to support such use cases.

I'll discuss this with @ifurnadjiev next week before building our M2.

[ablochberger]

RAP version used: 3.18

[ifurnadjiev]

Please try the latest stable build 3.21 M1 from our download page [1] and let us know if it's working for you.

[1] https://www.eclipse.org/rap/downloads/

[ablochberger]

I've tested with target platform https://download.eclipse.org/rt/rap/3.21/M1-20220415-1308/

The redirect with sendResponse now seems to do nothing (no error message)
The redirect from the filter class now shows the message: The application terminated unexpectedly with the following details:

Error: SyntaxError: JSON.parse: unexpected end of data at line 1 column 1 of the JSON data

  Stack: _handleSuccess@http://localhost:8080/rwt-resources/3210/rap-client.js:230:3729
setSuccessHandler/this._success@http://localhost:8080/rwt-resources/3210/rap-client.js:98:784
_sendWithFetch/

[ifurnadjiev]

Try:

public class RedirectFilter implements Filter {
  @Override
  public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
      throws IOException, ServletException {
    HttpServletRequest r = (HttpServletRequest) request;
    HttpSession session = r.getSession();
    String url = (String) session.getAttribute("redirect");
    Display display = (Display) session.getAttribute("display");
    if (display != null && url != null) {
      session.removeAttribute("redirect");
      session.removeAttribute("display");
      ProtocolMessageWriter messageWriter = new ProtocolMessageWriter();
      messageWriter.appendHead("redirect", url);
      messageWriter.createMessage().toJson().writeTo( response.getWriter() );
    } else {
      chain.doFilter(request, response);
    }
  }
}

[ifurnadjiev]

In your example response.sendRedirect(url) is not working because of CORS.

[ablochberger]

Thanks Ivan, the method with the ProtocolMessageWriter is working fine. But it does not work in the UI thread. Something like this works in any circumstance:

    public static void redirect( ServletResponse response, String url )
        throws IOException
    {
        if( Display.getCurrent() == null )
        {
            ProtocolMessageWriter messageWriter = new ProtocolMessageWriter();
            messageWriter.appendHead( "redirect", url );
            messageWriter.createMessage()
                .toJson()
                .writeTo( response.getWriter() );
        }
        else
        {
            ContextProvider.getProtocolWriter()
                .appendHead( "redirect", url );
        }
    }

[ablochberger]

The above code also works in RAP 3.18

[ablochberger]

But still there is one problem, when RAP is not yet loaded, the redirect does not work, because there is no script yet to execute the redirect. In this case I need to redirect with HttpServletRespone.sendRedirect

There are this three situations:

1. RAP not yet loaded, filter must redirect with HttpServletRespone.sendRedirect
2. RAP loaded, code in UI-Thread must redirect with ContextProvider
3. RAP loaded, code in non UI-Thread must redirect with ProtocolMessageWriter

I can detect 2 and 3, but not 1. Is there a way to tell, that RAP has not yet loaded on the client from a server side filter?
In the first case, a redirect with ProtocolMessageWriter would then only show the JSON in the browser

[ablochberger]

In this example, the first redirect then fails (Redirect.to contains the code from above):

    @Override
    public void doFilter( ServletRequest request, ServletResponse response,
        FilterChain chain ) throws IOException, ServletException
    {
        HttpServletRequest r = (HttpServletRequest)request;
        HttpSession session = r.getSession();
        Boolean first = (Boolean)session.getAttribute( "first" );
        if( first == null )
        {
            session.setAttribute( "first", true );
            Redirect.to( response, "http://some-auth-server:8080" );
        }
        else
        {
            String url = (String)session.getAttribute( "redirect" );
            if( url != null )
            {
                session.removeAttribute( "redirect" );

                Redirect.to( response, url );
            }
            else
                chain.doFilter( request, response );
        }
    }

Resulting with the page showing
{"head":{"redirect":"http://some-auth-server:8080"},"operations":[]}

[ifurnadjiev]

Usually the first request is a GET request, the other (after UI session is initialized) are POST. You could try to build something around it. Please note that ServerPush requests are also GET requests and you have to recognize them by "servicehandler" property.

[ablochberger]

So I can use HttpServletResponse.sendRedirect on GET requests that do not have the parameter servicehandler set.
The GET criteria works in my sample, I'll fix my redirect in my actual code (that uses ServerPushes) next then. Thanks for the heads up for the server push, I would have certainly missed that