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Arun Gupta is a technology enthusiast, a passionate runner, and a community guy who works for Sun Microsystems.

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Friday October 17, 2008

TOTD #49: Converting a JSF 1.2 application to JSF 2.0 - @ManagedBean

This is a follow up to TOTD #48 which showed how to convert a JSF 1.2 application to use new features of JSF 2.0. In this blog, we'll talk about a new annotation added to the JSF 2.0 specification - @ManagedBean.

@ManagedBean is a new annotation in the JSF 2.0 specification. The javadocs (bundled with the nightly) clearly defines the purpose of this annotation:

The presence of this annotation on a class automatically registers the class with the runtime as a managed bean class. Classes must be scanned for the presence of this annotation at application startup, before any requests have been serviced.

Essentially this is an alternative to <managed-bean> fragment in "faces-config.xml". This annotation injects a class in the runtime as a managed bean and then can be used accordingly.

Using this annotation, the following "faces-config.xml" fragment from our application:

<managed-bean>
        <managed-bean-name>cities</managed-bean-name>
        <managed-bean-class>server.Cities</managed-bean-class>
        <managed-bean-scope>request</managed-bean-scope>
    </managed-bean>
    <managed-bean>
        <managed-bean-name>dbUtil</managed-bean-name>
        <managed-bean-class>server.DatabaseUtil</managed-bean-class>
        <managed-bean-scope>request</managed-bean-scope>
        <managed-property>
            <property-name>cities</property-name>
            <value>#{cities}</value>
        </managed-property>
    </managed-bean>

is simplified to

@Entity
@Table(name = "cities")
@ManagedBean(name="cities", scope="request")
@NamedQueries({@NamedQuery(...)})
public class Cities implements Serializable {

and

@ManagedBean(name="dbUtil", scope="request")
public class DatabaseUtil {

@ManagedProperty(value="#{cities}")
private Cities cities;

The specification defines that managed bean declaration in "faces-config.xml" overrides the annotation.

A worthy addition to this annotation is "eager" attribute. Specifying this attribute on the annotation as @ManagedProperty(..., eager="true") allows the class to be instantiated when the application is started. In JSF 1.2 land, developers write their own ServletContextListeners to perform this kind of task. And this can of course be specified in "faces-config.xml" as <managed-bean eager="true">.

Section 11.5.1 of JSF 2.0 EDR2 specification defines several similar annotations that can be used to simplify "faces-config.xml".

Have you tried your JSF 1.2 app on Mojarra 2.0 ? Drop a comment on this blog if you have.

File JSF related bugs here using "2.0.0 EDR1" version and ask your questions on webtier@glassfish.dev.java.net.

Please leave suggestions on other TOTD (Tip Of The Day) that you'd like to see. An archive of all the tips is available here.

Technorati: totd javaserverfaces glassfish mojarra netbeans

Posted by Arun Gupta in web2.0 | Comments[10]