6. Use Dynamic Forms
In the Struts framework, ActionForm objects are used to capture HTML form data sent along with the request and also to provide data that can be used to help render the dynamic views. They are essentially JavaBean classes that extend from the Struts ActionForm class and have the option of overriding a couple of default methods.
This feature is a big time saver, as it helps to facilitate automatic presentation-layer validation. The only downside to ActionForms has been the need to create multiple ActionForm classes to hold the data for the various HTML forms. For example, if you have one page for the details of a user registration and another page for user preferences, you typically would need two separate ActionForm classes. One of the nicest features of Struts 1.1 is the notion of dynamic ActionForms.
Dynamic ActionForms, which are implemented by the
DynaActionForm class and
various subclasses, allow you to configure an ActionForm completely through the Struts
configuration file; there's no longer a real need to create actual concrete ActionForm
classes in your application. In the Struts configuration file, you can configure a
DynaActionForm for your application by adding a
<form-bean> element and setting the type to be the fully-qualified class name of the
DynaActionForm or one of its subclasses. The following example creates a dynamic ActionForm called
logonForm that contains
two instance variables:
<form-bean name="logonForm" type="org.apache.struts.action.DynaActionForm"> <form-property name="username" type="java.lang.String"/> <form-property name="password" type="java.lang.String"/> </form-bean>
This dynamic ActionForm can be used within Action classes and JSPs in the same way
that a regular ActionForm is used, with one small difference. With normal ActionForm
objects, we would provide get and set methods to get and set the data. In the example
above, we would have to provide a
setUsername() method and also a set for the
Because we are using a
DynaActionForm (which stores the variables in a Map), we need
to use the
set(name) method on the
DynaActionForm class, where the argument is the name of the instance variable we are trying to access. For example, if we
wanted to access the
username value from a
DynaActionForm, the code would look like this:
String username = (String)form.get("username");
Since the values are stored in a Map, we must cast the Object returned from the
There are several useful subclasses of the
DynaActionForm. The most important of these
is arguably the
DynaValidatorForm. This dynamic ActionForm is used with the Validator
to provide automatic validation using the common Validator package. This is another
nice feature that allows you to specify validation rules outside of the application source.
Combining these two features is a very attractive incentive for developers.
7. Use Visual Tools
Since the release of 1.0, there have been several Visual tools created to help create, modify and maintain the Struts configuration file. The configuration file itself is based on XML and for any medium to large-sized application, can grow to be unwieldy. To better manage this file once it has grown beyond what is considered easy-on-the-eyes, you might try using one of the GUI tools developed for this purpose. There are several commercial and open source tools available. Table 1 lists several of the tools available and URLs where you can find out more information.
Table 1. Struts GUI tools
|Easy Struts||Open Source||http://easystruts.sourceforge.net/|
|Struts Builder||Open Source||http://sourceforge.net/projects/rivernorth/|
For a more complete list of Struts GUIs (both free and commercial), visit the Struts resource page.
Chuck Cavaness is a graduate from Georgia Tech with degrees in computer engineering and computer science. He has built Java-based enterprise systems in the healthcare, banking, and B2B sectors. He is also the author of two O'Reilly books, Programming Jakarta Struts and Jakarta Struts Pocket Reference.
O'Reilly & Associates will soon release (November 2002) Programming Jakarta Struts.
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