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Java Forum / General / August 2006Servlets, send redirect and request scope
In a typical (MVC1) application. You have a HTML-FORM posting to servlet-A and getting request parameters/values from the request object. HTML-FORM ==> Servlet-A If I have to put a redirect in between the form and A. The request values are lost. Is there a generic way to restore those request values. I could put all the keys/values in a session object and then recollect the values in the servlet. But, I wish there was a generic way that possibly avoided using the session object. HTML-FORM ==> response?.sendRedirect ==> Servlet-A Something like response.putRequestValue... Berlin Brown wrote: > In a typical (MVC1) application. You have a HTML-FORM posting to > servlet-A and getting request parameters/values from the request [quoted text clipped - 11 lines] > > Something like response.putRequestValue... Why not use forward instead of redirect ? (that will keep request info) Arne Security reasons. It is needed to do the redirect. > Berlin Brown wrote: > > In a typical (MVC1) application. You have a HTML-FORM posting to [quoted text clipped - 18 lines] > > Arne Berlin Brown wrote: > Security reasons. It is needed to do the redirect. Then sessions or a special cookie. Arne Yea, but it isnt as clean and not generic. For example, I would have find every instance of request 'getParameters' that existed at the end servlet and replace with the session getting code. I wish there was a way to fill in values in the request object, that way I wouldnt have to change any code at all. > Berlin Brown wrote: > > Security reasons. It is needed to do the redirect. > > Then sessions or a special cookie. > > Arne > Yea, but it isnt as clean and not generic. For example, I would have > find every instance of request 'getParameters' that existed at the end > servlet and replace with the session getting code. > > I wish there was a way to fill in values in the request object, that > way I wouldnt have to change any code at all. And with a modern servlet spec, there is! You'll still have to get the new information to the new request somehow. Once it's there, though, you can set up a servlet filter that builds a wrapped ServletRequest object and adds parameters and/or request attributes. Google on servlet filters for details.  SignatureChris Smith How would I do that. I know about filters. But what about in this context. Would I use the redirect to hit a 'filter'. > > Yea, but it isnt as clean and not generic. For example, I would have > > find every instance of request 'getParameters' that existed at the end [quoted text clipped - 8 lines] > object and adds parameters and/or request attributes. Google on servlet > filters for details. > How would I do that. I know about filters. But what about in this > context. > > Would I use the redirect to hit a 'filter'. Yes. For example, you might use something like this: 1. Set a session attribute before you redirect containing the desired request attributes and parameters. 2. Install a filter that intercepts all requests. - If the session attribute doesn't exist, then just pass the request along the chain without doing anything. - If the session attribute does exist, then build a wrapped request that returns the desired attributes and parameters, and pass that along the chain. SignatureChris Smith What you are saying makes sense, except for the last part. Let me add a little bit more pseudo code (note I have some of my code in there): public class TestReconnectServlet extends BaseServlet { doPost() { String theKey = request.getParameterKey(); String theValue = request.getParameter(theKey); Object arr [] = new Object[2]; arr[0] = theKey; arr[1] = theValue; session.setValue("mysession.before.redirect", arr); response.sendRedirect(GoToFilter?); } } public class TheFilter implements Filter { public void doFilter(ServletRequest reqBasic, ServletResponse respBasic, FilterChain chain) { HttpServletRequest req = (HttpServletRequest) reqBasic; HttpServletResponse res = (HttpServletResponse) respBasic; /// Here ????????? build up the request object? String key, value = session.getValue(arr); request .setValue(key, value); ... chain.doFilter(req, res); } } Hmm, this might actually work? response.sendRedirect(GoToFilter?); When I do the redirect, it is to the GoToFilter? > > How would I do that. I know about filters. But what about in this > > context. [quoted text clipped - 14 lines] > that returns the desired attributes and parameters, and pass that > along the chain. > /// Here ????????? build up the request object? > String key, value = session.getValue(arr); > request .setValue(key, value); Check the API docs for javax.servlet.http.HttpServletRequestWrapper. You'd build a subclass of that, and pass it to FilterChain.doFilter in place of the original ServletRequest. SignatureChris Smith Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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