[Springframework-developer] [ANN] - Spring Web Flow PR4 Released

[Keith D. <ke...@in...>]

Dear Spring Community,

I'm pleased to announce the release of Spring Web Flow Preview 4 (PR4).
This release aligns Spring Web Flow with Spring 1.2.2+, as Spring 1.2.2
introduced changes that broke compatibility with previous preview releases.

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
<http://sourceforge.net/project/showfiles.php?group_id=73357&package_id=1485
17> &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.  Bottom line, 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.

An example of configuring an entry action from a XML-based webflow
definition follows:

<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>

Any number of actions may be executed in order as part of a composite state
entry action.

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.

<action-state id="executeSearch">

      <action bean="searchAction"/>

      <transition on="success" to="displayResults"/>

      <exit>

            <action bean="auditAction" method="logResults"/>      

      </exit>

</action-state>

 

Multiple actions may again be specified-they will automatically be wrapped
in a CompositeAction.

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 a given Flow definition is calculated on a
per-request basis.  For example:

<bean id="flowExecutionManager"
class="org.springframework.webflow.execution.servlet.ServletFlowExecutionMan
ager">

      <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:

1.	For redirect expressions that evaluate against the request context,
for example:

redirect:/${sourceEvent.parameters.url}?attribute=${flowScope.foo}&attribute
2=${requestScope.bar}"

2.	For transition expressions that drive dynamic state transition
decisions:

      <transition on="${result == 'success' &&
${flowScope.selectedItinerary.price} &gt; 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

As shown in #3 above, 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 1.1 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