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<td class="page-title-pattern-first-line " style="padding: 0px; border-collapse: collapse; font-family: Arial, sans-serif; font-size: 14px; padding-top: 10px"> <a href="https://issues.shibboleth.net/jira/browse/IDP" style="color: #3b73af; text-decoration: none">Identity Provider</a> / <a href="https://issues.shibboleth.net/jira/browse/IDP-753" style="color: #3b73af; text-decoration: none"><img src="cid:jira-generated-image-static-improvement-99d1303c-7aab-45d9-a829-f2ba51d67359" height="16" width="16" border="0" align="absmiddle" alt="Improvement" style="vertical-align: text-bottom" /></a> <a href="https://issues.shibboleth.net/jira/browse/IDP-753" style="color: #3b73af; text-decoration: none">IDP-753</a>
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<td style="vertical-align: top;; padding: 0px; border-collapse: collapse; padding-right: 5px; font-size: 20px; line-height: 30px; mso-line-height-rule: exactly" class="page-title-pattern-header-container"> <span class="page-title-pattern-header" style="font-family: Arial, sans-serif; padding: 0; font-size: 20px; line-height: 30px; mso-text-raise: 2px; mso-line-height-rule: exactly; vertical-align: middle"> <a href="https://issues.shibboleth.net/jira/browse/IDP-753" style="color: #3b73af; text-decoration: none">Possible use of custom SWF machinery to address config limitations</a> </span>
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<td style="padding: 0px; border-collapse: collapse; font: normal 14px/20px Arial, sans-serif; padding: 2px 0 2px 5px; vertical-align: top"> <a class="user-hover" rel="tzeller@shibboleth.net" id="email_tzeller@shibboleth.net" href="https://issues.shibboleth.net/jira/secure/ViewProfile.jspa?name=tzeller%40shibboleth.net" style="color:#3b73af;; color: #3b73af; text-decoration: none">Tom Zeller</a>
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Configuration
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Created:
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23/Jun/15 3:30 PM
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<td style="padding: 0px; border-collapse: collapse; font: normal 14px/20px Arial, sans-serif; padding: 2px 0 2px 5px; vertical-align: top"> <a class="user-hover" rel="cantor.2@osu.edu" id="email_cantor.2@osu.edu" href="https://issues.shibboleth.net/jira/secure/ViewProfile.jspa?name=cantor.2%40osu.edu" style="color:#3b73af;; color: #3b73af; text-decoration: none">Scott Cantor</a>
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<p style="margin-top:0;margin-bottom:10px;; margin: 10px 0 0 0">There are a handful of issues we've encountered with the advanced use of SWF because of limitations on its built-in configuration code.</p>
<p style="margin-top:0;margin-bottom:10px;; margin: 10px 0 0 0">The core problem has to do with supporting multiple flow registries, with or without a parent/child relationship. While you can chain registries together, SWF does not have the concept of a "top-level" search for flows while assembling flows defined in a particular registry. What this means in practical terms is that inheriting from a flow only works if both flows are defined in the same registry. This breaks a lot of pretty valuable uses for multiple registries, such as exposing base flows to users to customize on top of.</p>
<p style="margin-top:0;margin-bottom:10px;; margin: 10px 0 0 0">I believe from memory that it's also impossible for a flow to call a subflow defined in a child registry. A parent registry can have flows that call its own flows, but they cannot call their child's flows. That also makes the concept of chaining fairly pointless because it's impossible to intermingle flows at different "levels".</p>
<p style="margin-top:0;margin-bottom:10px;; margin: 10px 0 0 0">One possibility might be to manage to substitute our own Registry implementation that does bi-directional checks for flows by tracking its child (or children?) and trying the whole tree before giving up.</p>
<p style="margin-top:0;margin-bottom:10px;; margin: 10px 0 0 0">The core logic that configures the type of FlowDefinitionRegistry to use is in the org.springframework.webflow.config.FlowRegistryFactoryBean factory bean class that is used by way of the org.springframework.webflow.config.FlowRegistryBeanDefinitionParser custom Spring parser.</p>
<p style="margin-top:0;margin-bottom:10px;; margin: 10px 0 0 0">Using a single registry also has concerns, even though it fixes the whole "multiple registry" problem by avoiding it. The registry implementation created by the classes above also has a limitation in supporting only one base-path for locating flow files. That base path can be leveraged in two ways: explicit flow lookup and pattern-based lookup.</p>
<p style="margin-top:0;margin-bottom:10px;; margin: 10px 0 0 0">The actual lookup of flow files is outside the registry classes inside org.springframework.webflow.config.FlowDefinitionResourceFactory which is created by the factory bean above. In fact it's that class that has the base location injected, not the registry.</p>
<p style="margin-top:0;margin-bottom:10px;; margin: 10px 0 0 0">The problem is that collecting up multiple locations where files might live for pattern-based lookup is only possible through SWF's repurposing of the classpath* syntax Spring supports in a limited way. And that works. But if specific explicit flows are also specified by path, the lookup of those flow resources occurs by directly invoking an ApplicationContext's ResourceLoader methods, and the getResource() method on those contexts typically will NOT support classpath*.</p>
<p style="margin-top:0;margin-bottom:10px;; margin: 10px 0 0 0">Currently we're supplementing existing special classes we use for ResourceLoader functionality to understand classpath* and degenerate to "first file found", which allows this to work, mostly without major risk.</p>
<p style="margin-top:0;margin-bottom:10px;; margin: 10px 0 0 0">To fix this limitation, remove the special logic, and support walking multiple base-location expressions with different assumptions, we would also need to override the factory bean, since it's the class creating the classes that are doing all this.</p>
<p style="margin-top:0;margin-bottom:10px;; margin: 10px 0 0 0">So both issues degenerate into "do we override the factory bean?", which will obviously mean duplicating code from SWF to create our own custom version.</p>
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