This is the consolidated list of changes between Tapestry versions 5.3 and 5.4. To upgrade to 5.4, most users who are not using deprecated features will be able to just update the dependency version in their Maven POM file or Gradle build script (or download the new JAR files) and the new version will just work, although the introduction of Bootstrap CSS will require some styling adjustments for most applications not already using Bootstrap. Please read carefully below before upgrading, and also review the How to Upgrade instructions.
Incompatible APIs
JavaScriptSupport
Some existing methods of JavaScriptSupport were changed from returning void, to returning the JavaScriptSupport instance, to allow for chaining of calls. This interface is consumed by end-user code, but not generally implemented by end-user code.
Breaking Features
ClassFactory Removed
Tapestry's use of the Javassist bytecode library has been completely removed, along with many related services, such as ClassFactory, that were deprecated in 5.3. Use PlasticProxyFactory instead. Most users will not be affected by this unless they relied on Tapestry's dependency on Javassist.
ClientBehaviorSupport Functionality Removed
This service collected details about zone usage, including the client-side behavior associated with FormFragments. This interface is only kept for binary compatibility in Tapestry 5.4; the implementation no longer does anything but throw exceptions and will be removed in 5.5 or later.
FormInjector Removed
The FormInjector component was removed; it was intended for use only inside the AjaxFormLoop component (which was rewritten in 5.4 and no longer uses FormInjector). FormInjector was not widely used elsewhere, if it was used at all.
MarkupWriterFactory API Changed
The MarkupWriterFactory interface has 3 new methods, added to support the HTML5 rules for element endings. If you have any classes that implement MarkupWriterFactory (which is rare), they'll need to be modified to implement the new methods. As noted in the Javadocs, use JavaScriptSupport directly instead.
Injected Scripts at Bottom
In prior versions of Tapestry, JavaScript libraries injected into the page (via the @Import annotation, or via JavaScriptSupport), were injected into the <head> element of the HTML page, either at the end of the element, or before any existing <script> element.
With this release, the Tapestry integrates with RequireJS to dynamically load libraries. This may affect a small number of JavaScript libraries, such as Google Analytics that need to be placed at the top of the page; in those cases, the library should be added to the template of your application's main layout component, instead of relying on @Import and JavaScriptSupport.
No Redirect On Form Validation Errors
In prior releases of Tapestry, when a client-side form was submitted and there were server-side validation errors, Tapestry would perform a redirect-after-post to re-render the page; this meant that the ValidationTracker object that stores validation errors would, itself, need to persist to the new render request, causing a server-side session to be created. Starting in 5.4, the default behavior for server-side validation exceptions is to re-render the page content immediately, within the same request; this obviates the need to use a persistent field to store the tracker.
New Features
Component field visibility
In prior versions of Tapestry, all instance fields of components had to be visibility private; starting with versions 5.3.2 and 5.4, this has been relaxed. Component fields may be protected, or package private (that is, no visibility modifier). Fields that are final, or annotated with @Retain may even be public. In any case, this makes it easier for pages to work with other pages in the same package, and for subclasses to more easily access the fields (including parameter fields, or injections) provided by base classes. This feature should be used with care, as it can lead to designs that are more difficult to maintain.
JavaScript Modules
Prior releases of Tapestry primarily organized client-side logic in terms of JavaScript libraries. These libraries can be declaratively imported into the page (either during a full-page render, or during an Ajax partial page update). In addition, libraries can be combined together into stacks, which (in a production application) are combined into a single virtual asset.
The library approach is fundamentally limited in a number of ways, including namespace pollution and dealing with dependencies between libraries. Tapestry 5.4 introduces a parallel mechanism, based on RequireJS and the Asynchronous Module Definition as a way to speed up initial page load and organize client-side JavaScript in a more expressive and maintainable way.
Client-side API for invoking server-side events
Tapestry 5.4.2 adds an API which makes it easy for server-side events to be invoked from JavaScript. In the server-side, you first need to annotate the event handler methods you want exposed with the new @PublishEvent annotation. Then, in JS, all you need to do is to call the t5/core/ajax function with the server-side event name/type in the url parameter and with an options parameter containing an element property, be it null or specifying an DOM element to be used as the starting point for finding the event information. More details in the Ajax and Zones page.