The XSnapshot sample application illustrates how to use XSnapshot in a typical multi-tier Java web application, and specifically, how to apply it for data binding between ActionForms and the persistent domain model using Hibernate. This document describes the architecture of the sample application and how to build/run it.
build/ (produced by Ant, wiped by "ant clean") src/ (Java source; package net.sf.xsnapshot.sample) jsp/ (JSPs and XML descriptors)
The "business" subpackage contains the service layer. This is where the business logic of the application is performed. If the application is distributed, this is the layer that will be accessed remotely as a web service.
The business layer is fairly simple, and most of the methods are just database CRUD operations and call Hibernate directly. In more complex applications, you could move the dependency on persistence to a layer of DAO objects.
The "data" subpackage contains the domain model objects. These objects contain XDoclet tags for both Hibernate and XSnapshot.
The "presentation" subpackage contains presentation layer classes. All of the Struts form beans and actions go here.
"customType" contains some data structures and BeanUtils converters.
The control flow is:
This application demonstrates using XSnapshot to generate ActionForms with
data bindings to an underlying POJO domain model. The data binding is
declared with the XSnapshot tags, by defining a "form" snapshot that
ActionForm (or ValidatorActionForm, etc.)
This autogenerated class might be extended, to add a constructor to initialize nested objects (to ensure they aren't null), or to optionally add a validate/reset method. So the actual form bean class referenced from struts-config.xml may be a subclass of the generated class.
Of particular interest is date handling. Some of our objects have Date properties, which cannot be copied into the form bean verbatim the same way Strings are. Instead, we replace the Date property with a
DateInputModel, which in turn has three of its own properties (year, month, day). The HTML form in the JSP uses the dotted-introspection notation to set these nested properties (e.g.,
<html:select property="dateOfBirth.month">). Then, when the Action that processes this form uses XSnapshot to convert the form bean snapshot back to the POJO model, a converter (declared in the @xsnapshot.property tag) will be invoked to convert DateInputModel into a Date.