JavaServer Faces

Creating Objects Automatically as They Are Needed

With the converters in place, Example 6-4 works great, but there’s still a bit of magic left. You may be asking yourself how the reportHandler variable gets its value; it’s actually done automatically by JSF when the variable is first needed. JSF creates and configures instances of classes defined in the JSF faces-config.xml file for variables that are referenced in a value expression. Let’s take a closer look at this feature.

Example 6-5 shows the reportHandler variable declaration in the faces-config.xml file for the sample application, minus details that are not relevant for the examples in this chapter.

Example 6-5. ReportHandler declaration in faces-config.xml

<faces-config>
  ...
  <managed-bean>
    <managed-bean-name>reportHandler</managed-bean-name>
    <managed-bean-class>
      com.mycompany.expense.ReportHandler
    </managed-bean-class>
    <managed-bean-scope>session</managed-bean-scope>
    ...
  </managed-bean>
  ...
</faces-config>

The <managed-bean> element declares a variable that the application uses. The variable is mapped to a class that complies with the JavaBeans specification rules on naming conventions for accessor methods and has a public no-arguments constructor—hence, the bean reference in the element name.

All three subelements shown in Example 6-5 are mandatory: the <managed-bean-name> element declares the variable name used to refer to instances of the class; the <managed-bean-class> element declares the fully qualified class name; the ...