This chapter shows you how to upgrade existing Web Flow 1 application to Web Flow 2. The core concepts behind the flow definition language have not changed between Web Flow 1 and 2. However, some of the element and attribute names have changed. These changes allow for the language to be both more concise and expressive. A complete list of mapping changes is available as an appendix. An automated tool is available to aid in the conversion of existing 1.x flows to the new 2.x style. The tool will convert all the old tag names to their new equivalents, if needed. While the tool will make a best effort attempt at conversion, there is not a one-to-one mapping for all version 1 concepts. If the tool was unable to convert a portion of the flow, it will be marked with a WARNING comment in the resulting flow. The conversion tool requires spring-webflow.jar, spring-core.jar and an XSLT 1.0 engine. Saxon 6.5.5 is recommended. The tool can be run from the command line with the following command. Required libraries must be available on the classpath. The source must be a single flow to convert. The resulting converted flow will be sent to standard output. java org.springframework.webflow.upgrade.WebFlowUpgrader flow-to-upgrade.xml Bean actions have been deprecated in favor of EL based evaluate expressions. The EL expression is able to accept method parameters directly, so there is no longer a need for the argument tag. A side effect of this change is that method arguments must be of the correct type before invoking the action. Inline flows are no longer supported. The contents of the inline flow must be moved into a new top-level flow. The inline flow's content has been converted for your convenience. Output mappings can no longer add an item to a collection. Only assignment is supported. The var bean attribute is no longer needed. All spring beans can be resolved via EL. The var element will place all variable into flow scope. Conversation scope was previously allowed. EL expressions are used heavily throughout the flow definition language. Many of the attributes that appear to be plain text are actually interpreted as EL. The standard EL delimiters (either ${} or #{}) are not necessary and will often cause an exception if they are included. EL delimiters should be removed where necessary by the updater tool. In Web Flow 1 there were two options available for configuring Web Flow, one using standard spring bean XML and the other using the webflow-config-1.0 schema. The schema configuration option simplifies the configuration process by keeping long internal class names hidden and enabling contextual auto-complete. The schema configuration option is the only way to configure Web Flow 2. The FactoryBean bean XML configuration method used in Web Flow 1 is no longer supported. The schema configuration method should be used instead. In particular beans defining FlowExecutorFactoryBean and XmlFlowRegistryFactoryBean should be updated. Continue reading Web Flow Schema Configuration for details. The webflow-config configuration schema has also changed slightly from version 1 to 2. The simplest way to update your application is modify the version of the schema to 2.0 then fix any errors in a schema aware XML editor. The most common change is add 'flow-' to the beginning of the elements defined by the schema. ]]> The flow executor is the core Web Flow configuration element. This element replaces previous FlowExecutorFactoryBean bean definitions. ]]> Flow execution listeners are also defined in the flow executor. Listeners are defined using standard bean definitions and added by reference. ]]> The flow-registry contains a set of flow-locations. Every flow definition used by Web Flow must be added to the registry. This element replaces previous XmlFlowRegistryFactoryBean bean definitions. ]]> The package name for flow controllers has changed from org.springframework.webflow.executor.mvc.FlowController and is now org.springframework.webflow.mvc.servlet.FlowController for Servlet MVC requests. The portlet flow controller org.springframework.webflow.executor.mvc.PortletFlowController has been replaced by a flow handler adapter available at org.springframework.webflow.mvc.portlet.FlowHandlerAdapter. They will need to be updated in the bean definitions. The default URL handler has changed in Web Flow 2. The flow identifier is now derived from the URL rather then passed explicitly. In order to maintain comparability with existing views and URL structures a WebFlow1FlowUrlHandler is available. ]]> Web Flow 2 by default will both select and render views. View were previously selected by Web Flow 1 and then rendered by an external view resolver. In order for version 1 flows to work in Web Flow 2 the default view resolver must be overridden. A common use case is to use Apache Tiles for view resolution. The following configuration will replace the default view resolver with a Tiles view resolver. The tilesViewResolver in this example can be replaced with any other view resolver. ... ]]> Web Flow 1 required Spring MVC based flows to manually call FormAction methods, notably: setupForm, bindAndValidate to process form views. Web Flow 2 now provides automatic model setup and binding using the model attribute for view-states. Please see the Binding to a Model section for details. Web Flow 1 used OGNL exclusively for expressions within the flow definitions. Web Flow 2 adds support for Unified EL. United EL is used when it is available, OGNL will continue to be used when a Unified EL implementation is not available. Please see the Expression Language chapter for details. Flash scope in Web Flow 1 lived across the current request and into the next request. This was conceptually similar to Web Flow 2's view scope concept, but the semantics were not as well defined. In Web Flow 2, flash scope is cleared after every view render. This makes flashScope semantics in Web Flow consistent with other web frameworks. Web Flow 2 offers significantly improved integration with JavaServerFaces. Please see the JSF Integration chapter for details. External redirects in Web Flow 1 were always considered context relative. In Web Flow 2, if the redirect URL begins with a slash, it is considered servlet-relative instead of context-relative. URLs without a leading slash are still context relative.