Programming Jakarta Struts, 2nd Edition [Electronic resources] نسخه متنی

8.3 Using JavaBeans with Struts Tags

In many cases,
you'll use the tags from the various tag libraries
in conjunction with JavaBeans. The JavaBeans may be ActionForms,
whose properties correspond to input fields in the HTML form. In
other cases, however, the beans will be ordinary value objects from
the model layer. These beans can be in any scope: page, request,
session, or application.

There are three ways to access the
properties of a JavaBean:

• Accessing simple properties

• Accessing nested properties

• Accessing indexed properties

8.3.1 Accessing Simple Properties

Accessing simple bean properties works similarly
to the JSP <jsp:getProperty> action. A
reference to a property named
"firstName" is converted into a
method call to getFirstName() or
setFirstName(value),
using the standard JavaBeans specification naming conventions for
bean properties.

Struts uses the Java introspection APIs to identify the names of the
actual property getter and setter methods, so your beans can provide
customized method names through the use of a
BeanInfo class. See the
JavaBeans
specification, available at http://java.sun.com/products/javabeans, for
more information.

8.3.2 Accessing Nested Properties

Nested references are used to access
a property through a hierarchy of property names separated by periods
(.), similar to the way that nested properties are accessed in
JavaScript. For example, the following property reference:

property="user.address.city"

is translated into the equivalent Java expression:

getUser( ).getAddress( ).getCity( )

If a nested reference is used in a setter (such as when an input form
is processed), the property setter is called on the last property in
the chain. For the above property reference, the equivalent Java
expression would be:

getUser( ).getAddress( ).setCity(value)

Nested properties are very convenient to use with custom tags. They
almost always are used with the property attributes of the supported
tags.

8.3.3 Accessing Indexed Properties

Subscripts can be used to access
individual elements of properties whose values are actually arrays,
or whose underlying JavaBeans offer indexed getter and setter
methods. For example, the following property reference:

property="address[2]"

is translated into the equivalent Java expression:

getAddress(2);

while the same property reference in a setter would call the
equivalent of:

setAddress(2, address)

As you can see from these examples, the subscripts used in indexed
references are zero-relative (that is, the first element in an array
is address[0]), just as is true in the Java language.