Dear Spring Community,

We are pleased to announce general availability of Spring Web Flow 2. Download | Documentation

Spring Web Flow is the project in the Spring Portfolio that focuses on providing the infrastructure for building and running rich web applications. As a Spring project, Web Flow builds on the Spring Web MVC framework to provide:

• A domain-specific-language for defining reusable controller modules called flows
• An advanced controller engine for managing conversational state
• First-class support for using Ajax to construct rich user interfaces
• First-class support for using JavaServerFaces with Spring

The modules of the Web Flow 2 distribution and their relationship with the Spring Framework are illustrated below:

What's in Web Flow 2

Spring Web MVC

The Spring Web MVC framework, a module of the Spring Framework distribution, provides the foundation for developing web applications with Spring using the proven ModelViewController paradigm. Each of the modules of the Web Flow distribution builds on this foundation.

Spring Web Flow

The Web Flow module is a MVC extension that allows you to define Controllers using a domain-specific-language. This language is designed to model user interactions that require several requests into the server to complete, or may be invoked from different contexts.

Spring JavaScript

Spring JavaScript is a JavaScript abstraction framework that makes it easy to write unobtrusive JavaScript to progressively enhance a web page with behavior. The framework consists of a public JavaScript API along with an implementation that builds on the Dojo Toolkit. Spring.js aims to simplify the use of Dojo for common enterprise scenarios while retaining its full-power for advanced use cases.

Spring JavaScript can work with any server-side framework. The Web Flow 2 distribution includes convenient integration between Spring JavaScript and Spring Web MVC for processing Ajax requests.

Spring Faces

The Spring Faces module contains Spring's support for JavaServerFaces. This support allows you to use JSF as a View technology within a familiar Spring MVC and Web Flow Controller environment. With this architectural approach, you combine the benefits of the JSF UI component model with the benefits of a Web MVC architecture. Spring Faces also includes a lightweight component library built on Spring JavaScript for declaratively enabling Ajax and client-side validation behaviors in a progressive manner.

Themes of the Web Flow 2 Release

In addition to introducing the new Spring Faces and Spring Javascript modules, the Web Flow 2 release effort addresses two major themes: Integration and Simplicity.

Integration

Across each of the modules, the Web Flow 2 distribution adds a number of interesting integrations that allow you to enrich your web applications. These integrations support:

• Using Spring Security to secure your flows in a declarative manner
• Using Tiles for JSP page composition and Ajax partial-rendering
• When using JSF, using Facelets for page composition and layout
• When using JSF, using Apache Trindad and JBoss RichFaces component libraries
• Using the Dojo widget system in a progressive and unobtrusive manner; a manner that degrades gracefully if JavaScript is not available on the client

Simplicity

The flow definition language has been simplified tremendously in Web Flow 2 while becoming more powerful overall. These simplifications include:

• An appoximate 50% overall reduction in lines-of-code when comparing a version 2 flow definition with its version 1 equivalent (example: version 2 vs version 1)
• A concise syntax for invoking actions using an Expression Language (EL), with support for both the Unified EL and OGNL
• Declarative model binding and validation, with support for convention-over-configuration
• Support for reuse at both the flow and state levels using flow definition inheritance
• Enhanced modularity, allowing a flow and its dependent resources to be packaged together in a self-contained bundle

Release Notes

• Web Flow 2 requires Java 1.4 or greater and runs on all major Java EE platforms including Tomcat, Jetty, Websphere, WebLogic, and JBoss.

• Web Flow 2 requires Spring Framework 2.5.4 or greater.

• Web Flow 2 has been certified by SpringSource as "Platform Ready" and is fit to run on the SpringSource dm Server in OSGi-enabled web applications.

Getting Started

• Get started using Web Flow by downloading the release and walking through the reference applications. Supplement with the documentation as you go to familiarize yourself with the feature set.

• To get started using a build system such as Maven or Ant+Ivy, access Web Flow artifacts from the Maven Central Repository.

• To get started using Web Flow in an OSGi environment on the SpringSource Application Platform, download the platform and get Web Flow bundles from the SpringSource Enterprise Bundle Repository.

Additional Community Resources

• Read the interview with Keith Donald and Jeremy Grelle of SpringSource describing what's new in the Web Flow 2 distribution in more detail

• Watch the Ajaxian.com interview where the release and Spring JavaScript are discussed with Dion Almaer.

• Get involved with the Web Flow 2 community on the Spring Community Forums

• Explore Spring Web reference applications on-line. The Spring Travel application showcases the integrated Web Flow 2 feature set and is included in the distribution. The SpringSource Enterprise Bundle Repository is a real-world application in production built on Spring 2.5 and Spring Web Flow 2.0.

• If you are an existing Web Flow 1 user, review the migration guide to help in upgrading to Web Flow 2. The WebFlowUpgrader tool automates the conversion of your flows to the version 2 syntax

• Submit bug reports and requests for enhancement using the Web Flow issue tracker

• Track updates to the Web Flow source repository with Fisheye

• Checkout the Web Flow source code from the Spring Project SVN Repository

• Watch for upcoming articles on Web Flow 2 by subscribing to springframework.org

InfoQ has a discussion thread summarizing the reactions to the announcement of the SpringSource Application Plaform. Michael Burke asked a great question on that thread which can be paraphrased as "forgetting the hype surrounding OSGi, what benefits can I expect to see if I port an application currently packaged as an EAR to OSGi bundles?".

I started answering this question on the InfoQ thread, but my answer was growing too long for a comment so instead I'll address it here.

The question is a good one. The main difference you will see in an OSGi-based application versus a traditional JEE EAR-based application is improved modularity. So the question becomes, does this improved modularity bring me any benefits, and if so what are they? The book "Design Rules, The Power of Modularity" gives a very thorough treatment of the question. It's great background but I get that feeling that Michael may be looking for something a little less theoretical than what you'll find in that book…

One of the main advantages of the SpringSource Application Platform is its ability to provision dependencies on an as-needed basis. The benefits of this are two-fold: it ensures that the Platform's memory footprint is as small as possible and it allows applications to be deployed without encapsulating all of their dependencies in a monolithic deployment unit, e.g. a WAR file. To take advantage of these capabilities you will require an understanding of the Platform's provisioning repository and this blog intends to provide just that.

Where is the provisioning repository and how does it work?

• ext contains external dependencies that are provided with the Platform but are not part of the Platform itself.
• subsystems contains all of the subsystems that comprise the Platform.
• usr is initially empty and is intended to contain user-added dependencies, i.e. anything upon which your applications depend that is not already provided by the Platform.

Runtime provisioning

When a deployed application is started by the Platform its…

It's been great to hear so much discussion on the SpringSource Application Platform, online and on the floor here at JavaOne. One of the most insightful comments is from WebSphere transaction architect Ian Robinson:

Does any of this affect WebSphere? Well, nothing has changed in the core Spring framework. Regardless of what the future holds for the SpringSource Application Platform, the core Spring framework project remains complimentary to WebSphere. Like fish and chips.

The SpringSource Application Platform is constructed from OSGi bundles and supports applications which are also constructed from OSGi bundles. The Platform supports the standard features of OSGi, but it also supports some additional manifest headers. Several people have asked Why did SpringSource add proprietary headers? and What are the semantics of the new headers?, so this post explains the background motivation and the semantics of Import-Library and Import-Bundle.

Standard OSGi Bundle Support

So OSGi savvy developers can use the Platform as a standard OSGi container and benefit from Platform features such as:

• the ability to deploy bundles using the Admin Console or by dropping bundles in the Platform's pickup directory,
• diagnostics such as resolution failure diagnosis, application specific trace, and automatic deadlock detection,
• strong integration with Spring and Spring Dynamic Modules, for developers who want to use these frameworks, and
• automatic provisioning of dependencies from a repository.

Additional Requirements of Enterprise Applications

Well, some steps in the process are relatively easy, especially if good software engineering practices have been followed and the code has been organised into service, domain, and infrastructure components. These components can be converted into bundles and the dependencies between them expressed using standard OSGi Import-Package and Export-Package headers in META-INF/MANIFEST.MF.

A more difficult step is expressing dependencies on enterprise frameworks such as Spring and Hibernate. It is entirely possible to express these dependencies using standard OSGi Import-Package and Require-Bundle headers, and this is exactly what you should do if your aim is to create OSGi bundles which will run in other OSGi containers, but this approach has some hidden costs.

Firstly, the developer has to decide precisely which packages comprise a given framework. It isn't sufficient merely to import the packages the application code uses, as several enterprise frameworks weave further dependencies into the bytecode of the application when the application is loaded. The developer has to discover, probably by trial and error, which additional implementation packages to import to ensure correct behaviour of the woven application.

Then there is the chore of migrating from one version of a framework to the next where the precise set of packages comprising the framework has changed. The additional packages required for weaving are typically not defined by a public contract and so are subject to change.

Additionally, the resultant package imports don't properly capture the design intent, which makes maintaining or extending the application more difficult in the future.

We really don't want to impose these burdens on our users, so we created some additional SpringSource Application Platform specific manifest headers, Import-Library and Import-Bundle, as convenient ways of expressing dependencies on enterprise frameworks. As you'll see below, these headers are really just syntactic sugar which are expressed in terms of standard OSGi package imports.

Import-Library

    Import-Library: <librarySymbolicName>;version=<versionRange>

If you are unfamiliar with OSGi version range notation, by far the most commonly used forms are minimum version ranges such as 2, meaning version 2 or later, and half-open ranges such as [2.2.1,2.2.2), meaning any version between 2.2.1 inclusive and 2.2.2 exclusive. If version=<versionRange> is omitted, together with the semicolon delimiter of course, then the default range includes all versions.

For each library import, the Platform selects the library with the given symbolic name and the highest version in the given version range available in the Platform's repository. The Platform then replaces the library import with a set of package imports which match all the packages exported by the bundles of the library. The Platform detects the situation where a bundle imports two or more libraries which export a common package, issues an appropriate log message, and fails to install the importing bundle.

So, for example, the following header imports some version of the Spring Framework library between 2.5.4 inclusive and 2.5.5 exclusive:

    Import-Library: org.springframework.spring;version="[2.5.4,2.5.5)"

Optional Library Import

    Import-Library: <librarySymbolicName>;version=<versionRange>;resolution:=optional

If resolution is not specified, or is specified as mandatory, the bundle containing the import library header will fail to install if there is no library with the given symbolic name and a version in the given range. But if resolution:=optional is specified, the library import will be ignored if no suitable library is available.

So, for example, the following header imports some version of the Spring Framework library from 2.5 onwards, but is ignored if no suitable library is available:

    Import-Library: org.springframework.spring;version="2.5";resolution:=optional

Importing More than One Library

    Import-Library: org.foo.p;version="[1,2)",org.bar.q;version="[2,3)"

Import-Bundle

As you would expect, for each imported bundle, the Platform selects the bundle with the given symbolic name and the highest version in the given version range available in the Platform's repository. The Platform then replaces the bundle import with a set of package imports matching the packages exported by the bundle.

So, for example, the following header imports the Hibernate Object-Relational Mapper bundle:

    Import-Bundle: com.springsource.org.hibernate;version="[3.2.6,3.2.7)"

Why not Overload Require-Bundle?

Well, we wanted Require-Bundle to retain its standard semantics, including the ability to marry together pieces of a split package. But we wanted Import-Library and Import-Bundle to have the same underlying semantics as Import-Package which avoid the complexities of split packages.

We also anticipate that, as the Platform evolves over time, we'll need to add further directives to Import-Library and Import-Bundle which would not be appropriate to add to Require-Bundle.

What Next?

For users who want to take advantage of the Platform's headers, but who need to produce bundles which will run on other OSGi containers, we plan to produce a tool which will replace the Import-Library and Import-Bundle…

Dear Spring community,
We are pleased to announce that Spring Batch 1.0.1.RELEASE has been released!

Downloads | Site | Changelog

This release focuses on bug-fixes and improvements in documentation.

Since we released the SpringSource Application Platform last Wednesday, numerous developers have downloaded the 1.0.0 beta and started taking the Platform for a test drive. As a result, people have begun asking, "How can I deploy my apps on the Platform, and what kind of deployment and packaging options do I have?" Moreover, developers are eagerly requesting to see working samples. In response, the S2AP team will be releasing several sample applications over the coming weeks demonstrating these features and more, but before you get your hands on these samples, I'd like to give you a high-level…

Dear Spring community,

I'm pleased to announce that Spring Web Services 1.5.1 has been released!

Downloads | Site | Changelog | Announcement

This is the first bug fix and enhancement release in the Spring-WS 1.5 series. It fixes all bugs reported since 1.5.0 and introduces various enhancements throughout the framework:

• Introduced a Spring JMS MessageConverter that uses OXM marshallers
• Introduced a Spring MVC View that uses OXM marshallers
• Fixed WS-Security signatures when using WSS4J in combination with SAAJ messages
• Support for timeouts on HTTP transports
• Support for Castor 1.2, see note below
• Airline sample now uses Spring Security

and more. Please see the changelog for details.

Please note that - due to a backwards compatibility issue - the CastorMarshaller now requires Castor 1.2 or higher.

Cheers,

Arjen Poutsma
Spring Web Services Lead

A lot of people have been asking what exactly the SpringSource Application Platform does for Spring applications to make them run well under OSGi, over and above what you can get out of the box with OSGi and Spring Dynamic Modules. Adrian’s post yesterday highlighted some of the general issues, now lets look at a few of the details.

The three most challenging aspects of running Spring applications on OSGi are:

• Load-time weaving
• Classpath scanning
• Thread context classloader management

The remaining, but less interesting, issues include: JSP support, TLD scanning, annotation matching and resource lookups. Overall, there was a decent-sized set of issues that needed to be solved to make applications deploy smoothly.

Load-time weaving

Load-time weaving was one of the most problematic features to support in a robust manner. At the basic level, it requires hooking into the Equinox ClassLoader so that standard ClassFileTransformers can be attached and used during the defineClass calls. On top of this, many uses of LTW require access to a throwaway ClassLoader that can be used to inspect types to decide what needs to happen during the weave, without affecting the real ClassLoader.

This base level of support was actually reasonably simple to achieve. The difficulty comes in when weaving is driven by classes in one bundle, but classes in another bundle need to be woven. This is pretty common in enterprise applications where one bundle contains domain entities and another contains types that use a JPA EntityManager. The Platform takes care of this complexity by ensuring that all bundles in an application can be woven with the appropriate ClassFileTransformers.

When you start propagating weaving across to other bundles, you really need to know when to stop. If you simply apply weaving to all bundles, then applications will interfere with each other. The Platform prevents this from happening by explicitly scoping weaving so that it applies only to modules in the application.

Another issue with LTW is that it complicates refresh. When a bundle is refreshed, OSGi will refresh all the bundles that depend on it. This means that, in the example I gave above, refreshing the domain bundle will cause the EntityManager bundle to be refreshed. However, refreshing the EntityManager does not refresh the domain bundle, meaning that weaving is possibly out of sync. The Platform handles this by propagating refresh to other bundles that are affected by weaving.

Classpath scanning

With classpath scanning, the main issue is that Equinox doesn’t expose standard jar: and file: resources. The Platform puts an adapter in the middle so that libraries see the resource protocols that they expect. This has a nice side-effect of making a lot of third-party libraries work - it’s not just a fix for classpath scanning.

Thread context classloader management

Many third-party libraries use the thread context ClassLoader to access application types and resources. Each bundle in OSGi has it’s own ClassLoader, so therefore, only one bundle can be exposed as the thread context ClassLoader at any time. This means that if a third-party library needs to see types that are distributed across multiple bundles, it isn’t going to work as expected.

The Platform fixes this by creating a ClassLoader that imports all the exported packages of every module in your application. This ClassLoader is then exposed as the thread context ClassLoader, enabling third-party libraries to see all the exported types in your application.

This is just a small cross-section of the issues that are addressed by the Platform but hopefully it gives you an idea of what the Platform means for Spring Framework users.