Feedback requested: Redirect support in SWF

**Keith Donald** · Apr 29th, 2006, 07:12 PM

We have extended/refined the support for redirects in Spring Web Flow; feedback on these refinements are much appreciated.

1.0 introduced 3 redirect types: "conversation redirect", "flow redirect", and "external redirect".

A conversation redirect allows redirect to the *current* (most recent) view-state of a conversation, at a single conversation URL, while the conversation remains active.

A flow redirect requests that a entirely new execution of another flow be launched--used to support flow chaining and restart use cases.

A external redirect redirects to an arbitrary external URL, with support for sending a flow execution key through the redirect.

1.0 RC1 introduces a 4th type, called a "flow execution redirect". This supports redirecting to *any* previously traversed view-state of a flow execution at a unique "flow execution URL", to support post->redirect->get semantics with full support for back, forward, and refresh buttons while the conversation remains active.

In addition, the semantics of "conversation redirect" and "flow execution redirect" are a bit different now--previously application view selections made by view states were cached through the redirect; now they're reconstituted via a new FlowExecution "refresh" operation on each redirect request. Note this causes any data in request scope of the request preceding the redirect to be lost (while data in flow scope is preserved of course).

"itemlist" and "numberguess" samples demonstrate the "conversation redirect" (notice how back doesn't make any sense as the URL is stable throughout the flow, and it is best suited for a "SimpleFlowExecutionRepository").

"sellitem" demonstrates the "flowExecutionRedirect". Notice how the URL changes on each submit and back/forward/refresh are fully supported. Also note how this is is suited for a "ContinuationFlowExecutionRepository" and does not make sense with client-side storage.

Notice how post->redirect->get semantics can be configured globally for all flows (see FlowExecutor.redirectOnPause property) or on a per flow basis (see view-state redirect prefixes in "view" attribute DTD). Of course, redirection is optional, and samples like Phonebook don't do any redirects, relying on continuations + page caching to get stable navigation button behavior.

Thoughts? We should release 1.0 RC1 once we are confident these remaining redirect challenges are right.

Keith

**robmoore** · Apr 30th, 2006, 10:48 AM

Hey, Keith,

Just a question. In the description of sellitem, you mention that the "URL changes on each submit". Perhaps I'm using the wrong version of SWF (I'm on 1.0 EA) but I'm not seeing this. The URL remains consistently http://localhost:8080/swf-sellitem/p...lowId=sellitem.

Thanks,

Rob

**Keith Donald** · Apr 30th, 2006, 11:15 AM

Yes, this is new in 1.0 RC1. Try out a 4/30 or > nightly build:
http://static.springframework.org/do...pring-webflow/

**kris_lander** · May 2nd, 2006, 06:40 AM

Sounds excellent Keith and I look forward to trying it out asap.

**robmoore** · May 2nd, 2006, 10:06 AM

Hi, Keith,

I was trying to run through the sellitem example but am encountering this exception when I try to start the flow (using Jetty6.0.0beta14):

Code:

2006-05-02 10:01:07,521 DEBUG [org.springframework.webflow.executor.support.FlowRequestHandler] - <Request initiated by [ServletExternalContext@290e1513 requestParameterMap = map['_flowId' -> 'sellitem']]>
:WARN:  EXCEPTION
org.springframework.web.util.NestedServletException: Request processing failed; nested exception is java.lang.ArrayIndexOutOfBoundsException: 0
Caused by: java.lang.ArrayIndexOutOfBoundsException: 0
        at org.springframework.webflow.ParameterMap.get(ParameterMap.java:144)
        at org.springframework.webflow.ParameterMap.get(ParameterMap.java:128)
        at org.springframework.webflow.executor.support.FlowExecutorArgumentExtractor.extractFlowExecutionKey(FlowExecutorArgumentExtractor.java:267)
        at org.springframework.webflow.executor.support.FlowRequestHandler.handleFlowRequest(FlowRequestHandler.java:100)
        at org.springframework.webflow.executor.mvc.FlowController.handleRequestInternal(FlowController.java:198)
        at org.springframework.web.servlet.mvc.AbstractController.handleRequest(AbstractController.java:153)
        at org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter.handle(SimpleControllerHandlerAdapter.java:45)
        at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:796)
        at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:727)
        at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:396)
        at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:350)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:747)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:860)
        at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:423)
        at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:350)
        at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:221)
        at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:539)
        at org.mortbay.jetty.Server.handle(Server.java:341)
        at org.mortbay.jetty.Server.handle(Server.java:311)
        at org.mortbay.jetty.HttpConnection.doHandler(HttpConnection.java:355)
        at org.mortbay.jetty.HttpConnection.access$1500(HttpConnection.java:38)
        at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:598)
        at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:487)
        at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:196)
        at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:293)
        at org.mortbay.jetty.nio.SelectChannelConnector$HttpEndPoint.run(SelectChannelConnector.java:710)
        at org.mortbay.thread.BoundedThreadPool$PoolThread.run(BoundedThreadPool.java:412)
:WARN:  Nested in org.springframework.web.util.NestedServletException: Request processing failed; nested exception is java.lang.ArrayIndexOutOfBoundsException: 0:
java.lang.ArrayIndexOutOfBoundsException: 0
        at org.springframework.webflow.ParameterMap.get(ParameterMap.java:144)
        at org.springframework.webflow.ParameterMap.get(ParameterMap.java:128)
        at org.springframework.webflow.executor.support.FlowExecutorArgumentExtractor.extractFlowExecutionKey(FlowExecutorArgumentExtractor.java:267)
        at org.springframework.webflow.executor.support.FlowRequestHandler.handleFlowRequest(FlowRequestHandler.java:100)
        at org.springframework.webflow.executor.mvc.FlowController.handleRequestInternal(FlowController.java:198)
        at org.springframework.web.servlet.mvc.AbstractController.handleRequest(AbstractController.java:153)
        at org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter.handle(SimpleControllerHandlerAdapter.java:45)
        at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:796)
        at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:727)
        at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:396)
        at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:350)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:747)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:860)
        at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:423)
        at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:350)
        at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:221)
        at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:539)
        at org.mortbay.jetty.Server.handle(Server.java:341)
        at org.mortbay.jetty.Server.handle(Server.java:311)
        at org.mortbay.jetty.HttpConnection.doHandler(HttpConnection.java:355)
        at org.mortbay.jetty.HttpConnection.access$1500(HttpConnection.java:38)
        at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:598)
        at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:487)
        at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:196)
        at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:293)
        at org.mortbay.jetty.nio.SelectChannelConnector$HttpEndPoint.run(SelectChannelConnector.java:710)
        at org.mortbay.thread.BoundedThreadPool$PoolThread.run(BoundedThreadPool.java:412)
:WARN:  /swf-sellitem/pos.htm:
java.lang.ArrayIndexOutOfBoundsException: 0
        at org.springframework.webflow.ParameterMap.get(ParameterMap.java:144)
        at org.springframework.webflow.ParameterMap.get(ParameterMap.java:128)
        at org.springframework.webflow.executor.support.FlowExecutorArgumentExtractor.extractFlowExecutionKey(FlowExecutorArgumentExtractor.java:267)
        at org.springframework.webflow.executor.support.FlowRequestHandler.handleFlowRequest(FlowRequestHandler.java:100)
        at org.springframework.webflow.executor.mvc.FlowController.handleRequestInternal(FlowController.java:198)
        at org.springframework.web.servlet.mvc.AbstractController.handleRequest(AbstractController.java:153)
        at org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter.handle(SimpleControllerHandlerAdapter.java:45)
        at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:796)
        at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:727)
        at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:396)
        at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:350)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:747)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:860)
        at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:423)
        at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:350)
        at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:221)
        at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:539)
        at org.mortbay.jetty.Server.handle(Server.java:341)
        at org.mortbay.jetty.Server.handle(Server.java:311)
        at org.mortbay.jetty.HttpConnection.doHandler(HttpConnection.java:355)
        at org.mortbay.jetty.HttpConnection.access$1500(HttpConnection.java:38)
        at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:598)
        at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:487)
        at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:196)
        at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:293)
        at org.mortbay.jetty.nio.SelectChannelConnector$HttpEndPoint.run(SelectChannelConnector.java:710)
        at org.mortbay.thread.BoundedThreadPool$PoolThread.run(BoundedThreadPool.java:412)
...

I'll try running under Tomcat next, but just thought you'd like to know.

Rob

**Keith Donald** · May 2nd, 2006, 10:38 AM

What version?

**Keith Donald** · May 2nd, 2006, 10:38 AM

What version of SWF?

**robmoore** · May 2nd, 2006, 10:39 AM

Last night's build.

**Keith Donald** · May 2nd, 2006, 10:48 AM

That is a bug. Will fix promptly and add a test case.

Keith

**Keith Donald** · May 2nd, 2006, 11:53 AM

Fixed. Good catch; I'm not sure why this showed up in Jetty just now, as the bug has been there. It's resolved now.

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