Now that we have described the example application that will be the basis of this chapter’s discussion, it’s time to start looking at how we can implement it using the Struts framework. Although Chapter 1 discussed the MVC pattern in the order of model, view, and then controller, it doesn’t necessarily make sense to follow that order as we explore the Struts components. In fact, it’s more logical to cover the components in the order in which the Struts framework uses them to process a request. Thus, we’ll discuss the components that make up the controller portion of the framework first.
The Struts framework is made up of approximately 300 Java classes, divided into 8 core packages (“approximately” is an appropriate term because the framework is continuously growing and being shaped). In this chapter, we’ll focus on only the top-level packages. Figure 3-4 shows the top-level packages and their dependencies within the framework.
Tip
The validator
package shown in Figure 3-4 does not represent the entire set of classes
and interfaces necessary for the Validator framework. These are only
the Struts-specific extensions necessary to use the Validator
framework with Struts.
The framework components are not arranged by what role they play in
the MVC pattern—actually, they are arranged a little
haphazardly. You might have noticed this by some of the circular
dependencies shown in Figure 3-4. This has to do
more with how fast the framework has evolved than with poor decisions
made by the designers. For example, the action
package contains classes for the controller, some that are used by
the view domain, and even a few that probably would have been better
off in the util package. While it may be confusing
at first, it’s not that hard to get accustomed to
where everything is. Table 3-1 enumerates the
top-level packages and provides brief descriptions of their purposes.
A few of these top-level packages also contain subpackages, which
will be covered in later chapters.
Table 3-1. Top-level packages in the Struts framework
|
Package name |
Description |
|---|---|
|
Contains the controller classes, the | |
|
Contains the “out-of-box”
| |
|
Includes the configuration classes that are in-memory representations of the Struts configuration file. | |
|
Contains the tag handler classes for the Struts tag libraries. | |
|
Contains the classes used by the Tiles framework. | |
|
Includes classes used for uploading and downloading files from the local filesystem, using a browser. | |
|
Contains general-purpose utility classes used by the entire framework. | |
|
Contains the Struts-specific extension classes used by Struts when
deploying the validator. The actual Validator classes and interfaces
are in the |
Now that you have a feel for the packages that are contained within the framework, it’s time to look at the layers in the Struts architecture.