Components
Components are the core elements that you will be creating in OA. Essentially, components include EJB components, Servlets, Filters, Events, JSP pages, JavaBean components, the major struts components, plus other items like XML files, HTML files, JSP custom tags, properties files and Java interfaces. Pretty much all developmental aspects of a J2EE application. Each component is made up of elements. The elements available to you will depend on the type of component you are developing. For example, a JavaBean component can have elements that are attributes, component connectors, constructors and methods. So the process of development is really the process of creating(or importing) components and adding elements.
Adding a new element will bring up a dialog where you will enter the necessary information for the type of element you are creating. For example, if you are creating an attribute for a JavaBean component, you will need to name your attribute, you can assign a default value and so forth. A right-click menu on your element will allow you to view the implementation, or the code, then tab back and forth between the two as necessary. As you add new elements, they will appear as sub-items under your component.
One of the cool things to see is the output window down below as you are developing. This will give you important messages to alert you to potential mistakes in your components. For example, in the screen capture you will see the message Servlet myServlet should implement doPost or doGet. Very helpful.
Assemblies
Once you have completed some of your application, inevitably you will want to deploy it for testing on your application server. OA simplifies the process of creating JAR, WAR and EAR files through the assemblies feature(View the assemblies screen capture). To create a WAR file, for example, you select the Assemblies tab in the ObjectAssembler section of the Explorer frame. Then under Web applications, select the application server where you want to deploy your application. This will bring up a dialog that includes the primary information to include in your web.xml deployment descriptor. As with other items edited in OA, you can also edit the descriptor manually and the Output Window will highlight potential errors. Your set, build then deploy.
J2EE Patterns and PCML
A review of OA wouldn't be complete without a discussion of J2EE patterns and PCML (Pattern and Component Markup Language). PCML is an OA unique (as of today) XML-based abstraction of patterns. It is precisely this aspect of OA that makes it stand out, not just as a mid-level development environment, but even in comparison to the enterprise level development environments of much larger software development companies.
In short, you edit patterns as you would other elements using the Patterns tab in the ObjectAssembler section of the Explorer window. Once you have selected a pattern, as you may expect, OA will give you messages in the Output Window explaining whether your application elements match the given pattern, along with suggestions as to what you might do to make them compliant.
You can see, especially given that you can create your own patterns, how powerful this tool can be to ensure consistent coding that conform to best practices, as well as saving development time by enforcing the use of patterns.
Using ObjectAssembler with Struts
One last item that should be mentioned is OA's support of Jakarta Struts. Struts is an open source project managed through Apache's Jakarta program (Jakarta is the J2EE portion of the larger Apache project). Struts was created to simplify development and enforce the MVC, or Model-View-Controller pattern. MVC separates the view interface, from the business logic model and controller(which handles input and output as well as security and such). Essentially, Struts is a framework that has evolved over the years to become a quite robust engine that can greatly shorten development time of fairly complex J2EE applications.
OA includes components and assemblies that are specific to Struts. This allows developers to fully capitalize on the Struts framework from within OA's visual interface. Creating Struts Actions, ActionForms and Plug-ins are as easy as creating JSP pages and JavaBeans components.
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