Programming Jakarta Struts

Extending Model Components

Because the Struts framework doesn’t provide a great deal of components for the model layer, extensions to these components are better discussed in other Java programming books. However, there are two classes that might be placed into the category of extensible model components. They aren’t the best representations of what a model component is, but they are responsible for holding model state.

The UserContainer and ApplicationContainer Classes

I’ve mentioned the UserContainer and ApplicationContainer classes in previous chapters without defining exactly what they are. These two classes are not part of the Struts framework—I created them as part of the example Storefront application. The purpose of these classes is to store user and application-specific information in instances of these classes, rather than in the HttpSession and ServletContext objects, respectively.

One of the problems with storing data in the HttpSession is that the interface to store and retrieve data from the session object is not strongly typed. In other words, the interface for any data is:

public void setAttribute( "permissionsKey", permissions );
public Object getAttribute( "permissionsKey" );

The client must be aware of the key at which the data is stored in order to put an object into or retrieve an object from storage. Some programmers prefer a more strongly typed interface instead:

userContainer.setPermissions( permissions );
userContainer.getPermissions(  );

Here, the client ...