jwma's Architecture - Model Element
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Model Design

The design of the Model element has been primarily driven by the requirement to enable a true seperation of application logic and presentation based on the MVC Model 2 architecture. However, there are some additional objectives:

• provide a simple view designer's perspective:
  The View element of the architecture should be designable, without requiring the designer to be an expert (Java) programmer.
• provide a simple controller programmer's perspective:
  The Controller element of the architecture should be (rather) easy to implement, allowing the model to be integrated with different server side technologies (i.e. frameworks).
• focus on server side mail client requirements:
  The JavaMail™ API is a very well done abstract design for writing mail software in Java. While it is suitable for writing server side mail clients, it does not provide any special support for this type of deployment.

The deployed basic model construct resulting from these requirements consists of:

1. a class (possibly wrapping a related javax.mail class, employing an association)
2. a simplified "accessors-only" interface

Figure 1 shows the abstract simplified model construct (left side) and jwma's folder implementation (right side) as example.

Figure 1: Basic Model Construct

However, not everything is implemented in such a basic "one class implements one interface" construct. When more convenience can be achieved for the view designer, a class might implement two or three simplified interfaces, each of which abstracts the actual implementation (for an example, see Figure 2).

Figure 2: Real Example from jwma

The View Designer's Perspective

A set of interfaces, exposing only accessor methods (following the JavaBeans nomenclature; i.e. get and is instance operations whenever suitable), defines the contract between the view designer and the model.
Figure 3 demonstrates an example using the JwmaTrashInfo. The left side shows the UML interface documentation, the right side a possible use in a JSP/HTML based view implementation. Code elements are highlighted with blue color. Note the htmlhelper instance, which is an utility class serving the purpose of keeping a view designer's life simple.

<%-- Trash status information --%> <table width="90%">  <tr>   <td width="100%"align="right">    <% if (trash.isEmpty()) { %>     <img border="0" src="images/trash_empty.png" alt="<i18n:message key="trashbin.empty"/>">    <% } else { %>     <a href="<%= htmlhelper.getFolderDisplayAction(trash) %>">      <img border="0" src="images/trash_full.png" alt="<i18n:message key="trashbin.full"/>">     </a>    <% } %>   </td>  </tr> </table> <%-- END: Trash status information --%>

Figure 3: Example use of JwmaTrashInfo in a JSP/HTML based View

The complete set of interfaces is documented in an annotated UML class diagram. Additional documentation can be found in the development section (add link).

The Controller Programmer's Perspective

The actual implementations of the interfaces providing the view designer's perspective represent the controller programmer's perspective. Exceptions to this pattern are only the newly introduced plugin constructs (see documentation). Figure 4 presents an example class and a related piece of controller code (based on a plain servlet).

/**  * Removes a mail identity.  *  * @param session a <code>JwmaSession</code> instance.  *  * @throws JwmaException if it fails to execute properly.  */ private void doRemoveMailIdentity(JwmaSession session, String uid)     throws JwmaException {   JwmaPreferencesImpl prefs = session.getPreferences();   //remove the instance   prefs.removeMailIdentity(uid);   //save   session.savePreferences();   //redirect   session.redirect(JwmaKernel.PREFERENCES_VIEW); }//doRemoveMailIdentity

Figure 4: Example use of JwmaPreferencesImpl in a plain Servlet based Controller

The complete set of interfaces and classes of the model is documented in an annotated UML class diagram.
(Note: It takes quite some space, because I have tried my best to unclutter it...)

Additional documentation can be found in the development section.

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