This schema defines Spring Web Flow's XML-based flow definition language.
The root "flow" element in this document defines exactly one flow definition. A flow definition is a blueprint for a carrying out a conversation with a single user.
A flow is composed of one or more states that form the steps of the flow. Each state executes a behavior when entered. What behavior is executed is a function of the state's type. Core state types include view states, action states, subflow states, decision states, and end states.
A flow definition has exactly one start state. Events that occur within states drive state transitions. ]]> A flow may also exhibit the following characteristics:

Be annotated with attributes that define descriptive properties that may affect flow execution. (See the <attribute/> element)
Be secured (See the <secured/> element)
Be a persistence context for managing persistent objects during the course of flow execution. (See the <persistence-context/> element)
Instantiate a set of instance variables when started. (See the <var/> element)
Map input provided by callers that start it (See the <input/> element)
Return output to callers that end it. (See the <output/> element)
Execute actions at start time and end time. (See the <on-start/> and <on-end/> elements)
Define transitions shared by all states. (See the <global-transitions/> element)
Handle exceptions thrown by during flow execution. (See the <exception-handler/> element)
Import one or more local bean definition files defining custom flow artifacts (such as actions, exception handlers, view factories, transition criteria, etc). (See the <bean-import/> element)

]]> The persistence context can be referenced from within this flow by the "entityManager" variable. ]]> For example

<state id="state" parent="flowId#stateId">

]]> Once paused, a view-state may be 'refreshed' by the user. A refresh causes the response to be reissued and then returns control back to the user.
A view state may be configured with one or more render-actions using the 'on-render' element. Render actions are executed immediately before the view is rendered.
A view state is a transitionable state. A view state transition is triggered by a user event. ]]> For example

<state id="state" parent="flowId#stateId">

]]> priceForm.jsp Can also be an evaluatable expression:

	${flowScope.myViewExpression}

The externalRedirect: prefix may be used to redirect to an external location, typically to interface with an external system or controller. External redirect query parameters may be specified using ${expressions} that evaluate against the request context. The supported formats for an encoded externalRedirect expression are:

	externalRedirect:
	externalRedirect:contextRelative:
	externalRedirect:serverRelative:
	externalRedirect:

For example:

	externalRedirect:/hotels/index
	externalRedirect:http://someOtherSystem?orderId=${order.id}&callbackUrl=${flowExecutionUrl}

The flowRedirect: prefix may be used to redirect to another flow:

	flowRedirect:myOtherFlow?someData=${flowScope.data}

For exotic usages, you may plug in a custom ViewFactory bean you define:

	${myCustomViewFactory}

When this attribute is not specified, the view to render will be determined by convention. The default convention is to treat the id of this view state as the view identifier. ]]> A decision state is a transitionable state. A decision state transition can be triggered by evaluating a boolean expression against the flow execution request context. To define transition expressions, use the 'if' element.
Examples:
A simple boolean expression test, using the convenient 'if' element:

    <decision-state id="requiresShipping">
	    <if test="sale.requiresShipping" then="enterShippingDetails" else="processSale"/>
    </decision-state>

]]> The form is:

	<if test="criteriaExpression" then="trueStateId" else="falseStateId"/>

]]> <if test="sale.requiresShipping" then="enterShippingDetails"/> ]]> For example

<state id="state" parent="flowId#stateId">

]]> A subflow state is a transitionable state. A transition is triggered by the subflow outcome that was reached. ]]> For example

<state id="state" parent="flowId#stateId">

]]> An end state is not transitionable; there are never transitions out of an end state. When an end-state is entered, an instance of this flow is terminated.
When this flow terminates, if it was the "root" flow the entire execution is terminated. If this flow was a subflow, its parent flow resumes. ]]> For example

<state id="state" parent="flowId#stateId">

]]> priceForm.jsp It can also be an evaluatable expression:

	${flowScope.myViewExpression}

The externalRedirect: prefix may be used to request a redirect to an external location, typically to interface with an external system or controller. External redirect query parameters may be specified using ${expressions} that evaluate against the request context. The supported formats for an encoded externalRedirect expression are:

	externalRedirect:
	externalRedirect:contextRelative:
	externalRedirect:serverRelative:
	externalRedirect:

For example:

	externalRedirect:/hotels/index
	externalRedirect:http://someOtherSystem?orderId=${order.id}

The flowRedirect: prefix may be used to redirect to another flow:

	flowRedirect:myOtherFlow?someData=${flowScope.data}

For exotic usages, you may plug in a custom ViewFactory bean you define:

	${myCustomViewFactory}

When this attribute is not specified, no final response will be issued. In this case, the caller is expected to handle this flow outcome. ]]> For example:

    <bean-import resource="orderitem-flow-beans.xml"/>

... would look for 'orderitem-flow-beans.xml' in the same directory as this document. ]]> Note: Cannot be used in conjunction with an exception based transition. ]]> <transition on="submit" to="state"/> ... which reads "on the occurrence of the 'submit' event, transition to 'state'"
Sophisticated transitional expressions are also supported when enclosed in a delimited expression:

	<transition on="${currentEvent.id == 'submit' &;amp;& flowScope.attribute == 'foo'}" to="state"/>

]]> The value of this attribute must be a fully-qualified java.lang.Exception class name (e.g. example.booking.ItineraryExpiredException). Superclasses of the configured exception class match by default. Use this attribute or the 'on' attribute, not both.
Note: Cannot be used in conjunction with a secured element. ]]> The value of this attribute may be a static state identifier (e.g. to="displayForm") or a dynamic expression (e.g. to="${flowScope.previousViewState}"). If no value is specified, this transition acts as a simple event handler and will not change the state of the flow. ]]> Note: This element configures a meta-attribute. For the attribute to be enforced, the flow execution must be observed by a SecurityFlowExecutionListener. ]]>