1.3.0 Lecture Managed Beans

8/14/2019 1.3.0 Lecture Managed Beans

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ICESOFT TECHNOLOGIES INC. www.icefaces.org

Managed Beans


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Managed Beans

JSF allows users to design a complex tree of namedPOJO Beans

Beans have a predetermined lifespan known as scope

Beans can be defined using:

Managed Bean Creation facility (faces-config.xml)

Java EE 5 annotations

Managed Beans also have a lifecycle which dependson their specified scope


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POJO Beans

Application developers have full control overapplication design

Full control gives you great flexibility in your designbut it can also expose you to common design errors


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Bean Names

Bean names uniquely identify the Bean within thecontext of the application

Follow the same naming conventions as Java classes,mixed case starting with lower case

Bean names can be defined in faces-config.xml

myBeanName org.mycompany.package.ClassName ...


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Bean Names

JSF 2 introduces the @ManagedBean annotation

Names can be specified with the name attribute@ManagedBean(name=someName)

If a name is not specified the class name is used asthe Bean name, mixed case starting with lower case

The eager attribute can be used to insure that a bean

is loaded in a non-lazy fashion@ManagedBean(name=someName, eager=true)

Note: import javax.faces.bean. ManagedBean;


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Bean Scopes

JSF 1.x originally defined four scope types:

Application

Lifespan continues as long as the web application is deployed

Session

Lifespan of the HttpSession, destroyed by session timeout ormanual invalidation

Unique to each user but share across multiple browser tabs

Request

Lifespan duration of an HTTP request received by the serverand response sent to client

No Scope

Bean isnt placed into scope

Application

Session


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Bean Scopes

JSF 2 introduces three new scopes:

View

Bean lasts the duration of the view

Page navigation or page refreshes cause the Bean to bedestroyed and reinitialized

Flash

Short conversation-style scope that exists for a single view

transition including reloads

Custom

Allows developers to implement their own custom scopebehavior


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Bean Scopes

Once a Bean is defined in the faces-config.xml or viaan Annotation it has a default of request scope

Bean scope can be defined explicitly in thefaces-config.xml

myBeanName org.mycompany.package.ClassName

application|session|view|request|flash


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Bean Scopes

How do I know which scope to use?

Try to avoid jamming all state in to the Session scope.

Start of with request scoped beans

If you need the Bean to live longer move it to view scopeand so on until you get the appropriate results

Bean scoping is a fine balance between memory usage anda rich user experience. In some instances, it can be difficultto have both


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Bean Scopes

Scopes can also be defined with annotations

@ApplicationScoped

@SessionScoped

@ViewScoped

@RequestScoped

@CustomScoped(value="#{someMap}")

@NoneScoped

Note: make sure to import:javax.faces.bean.Xscoped;


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Bean Lifecycle

JSF implementations running in a Java EE 5compliant container have access to two other

annotations: @PostConstruct

@PreDestroy

Methods on managed beans can be annotated:

@PostConstructPublic void myMethod(){ // initialization logic.}


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Bean Lifecycle

When the bean is initialized the method binding for@PostConstruct is called immediately after the Class is

initialized Convenient method for initialization data at construction

time

@PreDestroy is called just before the Bean is removed from thecontainer management

Bean scope plays an important role as to when this method iscalled

Can be handy for proactively cleaning up a memory foot printor un-registering a class from a listener


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End Presentation

1.3.0 Lecture Managed Beans

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