The Java EE 5 Tutorial (PDF) - Oracle Software Downloads

JavaBeans Components
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JavaBeans Component Design Conventions
JavaBeans component design conventions govern the properties of the class and govern the
public methods that give access to the properties.
A JavaBeans component property can be:
■ Read/write, read-only, or write-only
■ Simple, which means it contains a single value, or indexed, which means it represents an
array of values
A property does not have to be implemented by an instance variable. It must simply be
accessible using public methods that conform to the following conventions:
■ For each readable property, the bean must have a method of the form:
PropertyClass getProperty() { ... }
■ For each writable property, the bean must have a method of the form:
setProperty(PropertyClass pc) { ... }
In addition to the property methods, a JavaBeans component must define a constructor that
takes no parameters.
The Duke’s Bookstore application JSP pages bookstore.jsp, bookdetails.jsp, catalog.jsp,
and showcart.jsp, all located at
tut-install/javaeetutorial5/examples/web/bookstore2/web, use the
tut-install/javaeetutorial5/examples/web/bookstore2/src/java/com/sun/bookstore2/database/Book
JavaBeans component.
BookDB provides a JavaBeans component front end to the access object BookDBAO. The JSP pages
showcart.jsp and cashier.jsp access the bean
tut-install/javaeetutorial5/examples/web/bookstore/src/com/sun/bookstore/cart/ShoppingCart.ja
which represents a user’s shopping cart.
The BookDB bean has two writable properties, bookId and database, and three readable
properties: bookDetails, numberOfBooks, and books. These latter properties do not correspond
to any instance variables but rather are a function of the bookId and database properties.
package database;
public class BookDB {
private String bookId = "0";
private BookDBAO database = null;
public BookDB () {
}
public void setBookId(String bookId) {
this.bookId = bookId;
}
The Java EE 5Tutorial • June 2010