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Spring Web Flow PR4 Released

Dear Spring Community,

I’m pleased to announce the release of
Spring Web Flow Preview 4 (PR4). This release aligns Spring Web Flow
for use with Spring 1.2.2+.

This will be the last Web Flow preview release; the next release will be 1.0 RC1. To download, access: http://sourceforge.net/project/showfiles.php?group_id=73357&package_id=148517

Note: there are some incompatible changes between PR3 and PR4. This includes a root package rename from org.springframework.web.flow to org.springframework.webflow,
noting Web Flow’s status as a standalone module deserving of a
top-level package.  For a complete list of changes, access the
change log here: http://opensource.atlassian.com/confluence/spring/display/WEBFLOW/Change+Log

Special
note for WebFlow Portlet users: PR4 does not ship Portlet MVC
integration.  Portlet MVC users will need to wait for Web Flow RC1
in a few weeks when Portlet MVC has been integrated for shipment with
Spring 1.3. We apologize for any short-term inconvenience here: expect
better Portlet MVC integration + the sample app to be back in the
coming weeks.

Contained within this PR4 release are a number of new and noteworthy enhancements. Here are some of them:

State entry actions

Any
instance of any State type may be configured with an entry action that
will be executed when the state is entered.  This facilitates
generic state setup logic. For example, a ViewState could set an entry
action to execute arbitrary pre-render logic. Such pre-render logic
might load reference data to populate form drop downs.  Any number
of actions may be executed in order as part of a composite state entry
action:

<view-state id="displayCriteria" view="searchCriteria">
<entry>
<action bean="searchFormAction" method="setupForm"/>
<action bean="searchFormAction" method="setupReferenceData"/>
</entry>

<transition on="search" to="executeSearch">
<action bean="searchFormAction" method="bindAndValidate"/>
</transition>
</view-state>

TransitionableState exit actions

Any
instance of any TransitionableState type may be configured with an exit
action that will be executed when the state is exited. This facilities
generic state tear-down logic.  Multiple actions may again be
specified and they will automatically be wrapped in a CompositeAction.

<action-state id="executeSearch">
<action bean="searchAction"/>
<transition on="success" to="displayResults"/>
<exit>
<action bean="auditAction" method="logResults"/>
</exit>
</action-state>

Flow Execution Listener Criteria

Before
PR4 there was no easy way to define for a set of flow definitions which
listeners should observe launched flow executions.  The new
FlowExecutionListenerCriteria provides a pluggable strategy where the
set of applicable listeners for executions for a given Flow definition
is calculated on a per-request basis.

<bean id="flowExecutionManager"
class="org.springframework.webflow.execution.servlet.ServletFlowExecutionManager">
<property name="listenerMap">
<map>
<entry value="*">
<key>
<list>
<bean class="example.Listener1"/>
<bean class="example.Listener2"/>
</list>
</key>
</entry>

<entry value="sampleFlowA">
<key>
<list>
<bean class="example.Listener3"/>
</list>
</key>
</entry>
</map>
</property>

</bean>

The
above Spring configuration attaches Listener 1 and 2 to executions of
all flows (*), while Listener 3 is only attached to "sampleFlowA".

Greatly enhanced expression language support

One
of the real strengths in this release is the continued progress with
the new Spring data binding module.  Contained within
spring-binding is an expression parsing and evaluation abstraction
seamlessly integrated with a robust type conversion facility. 
These two in combination allow for arbitrary strings representing one
or more expressions like “Announcement: ${org} ${product} ${release} is
out!” to be consumed and converted to evaluateable expressions
utilizing any expression language, with OGNL being the default. 
Spring Web Flow leverages this machinery in several places including
redirect expressions, transition expressions, and attribute mapping
expressions:

  1. For redirect expressions that evaluate against the request context, for example:
    redirect:/${sourceEvent.parameters.url}?attribute1=${flowScope.foo}&attribute
    2=${requestScope.bar}"
  2. For transition expressions that drive dynamic state transition decisions:
    <transition on="${result == ‘success’ && ${flowScope.selectedItinerary.price} > 500.0" to="requireCreditCheck"/>
  3. For attribute mapping expressions that map attributes between two sources:
    <subflow-state id="browseDetails" flow="detailFlow">
    <attribute-mapper>
    <input value="${sourceEvent.parameters.id}" as="someBean.id" from="string" to="long"/>
    </attribute-mapper>

    </subflow-state>

Enhanced attribute-mapper type-conversion support

The
”from” and “to” attributes of input and output mapping elements can be
used to specify type conversion rules.  So the definition:

<input value="${sourceEvent.parameters.id}" as="someBean.id" from="string" to="long"/>

says:

Convert the value of ${sourceEvent.parameters.id} from a string to a long and set the long result at someBean.id.

Session-based TransactionSynchronizer strategy

A
new TransactionSynchronizer that manages a transaction token in
HTTP-session scoped storage is new for PR4.  It is ideal for
working with flows that are leveraging continuations and need to
prevent duplicate application transactions from occurring.

New convenience action implementations

The
webflow.action package now sports several new action implementations
including: CompositeAction, DelegatingAction, and GuardedAction.

JMX-enabled flow execution statistics

The
sellitem sample now demonstrates the capability to collect global
statistics on all Web Flows using the JMX management protocol, and
monitor those statistics using any JMX client like the JDK 1.5
JConsole.  Future web flow releases will enhance this capability
to allow for management and monitoring on a per flow execution basis.

Simplified and improved Struts integration

Struts
1.x integration has been greatly simplified with PR4 and aligned with
Spring 1.2.2’s introduction of the SpringBindingActionForm.  There
is no longer a need for a special FlowActionMapping as all
webflow-specific configuration is now managed by Spring.  See the
birthdate sample application for a concrete example.

Other:

Improved javadoc, error messages, and logging

Much improved build system with “one-step” sample application build/deployment

Erwin
and I must thank Colin Sampaleanu for putting together one heck of a
build system to manage the overall development and release
process.  You will find when you download PR4 that building and
deploying the sample applications, as well as any component of Spring
Web Flow (such as the project itself or the binding module) to be
simple and easy, with careful, automatic jar file management. 
This “common-build” system is Ant 1.6.x based and leverages Ivy for jar
dependency management

These are just some of the new
features of this release.  For a full list of changes, see
http://opensource.atlassian.com/confluence/spring/display/WEBFLOW/Change+Log

As always, we very much value your feedback.  Expect Web
Flow 1.0 RC1 by the end of July with Portlet MVC and JSF integration.

Cheers,

Keith Donald
Erwin Vervaet

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