Best Practices for JSF, Gameduell 2013

JSF Best PracticesEdward Burns@edburns http://slideshare.net/edburns/Consulting Member of Staff, Oracle


Program Agenda

Review of the JSF Lifecycle

Conversion and Validation

JSF Navigation Review


The following is intended to outline our general product direction. It is intended for information purposes only, and may not be incorporated into any contract. It is not a commitment to deliver any material, code, or functionality, and should not be relied upon in making purchasing decisions. The development, release, and timing of any features or functionality described for Oracle’s products remains at the sole discretion of Oracle.


Lifecycle Review


Review: The Lifecycle Orchestrates MVCThe Baseball and Apple Pie of Web apps

• Data Conversion and Validation• Page Flow• Database integration

• I18N, L10N, A11Y• Support CSS, Markup based

layout• User Friendliness!



• The JSF Lifecycle uses some elements of the strategy design pattern– Define a family of algorithms

– Encapsulate each one

– Make them interchangeable

• For each Lifecycle phase, traverse theUIComponent hierarchy and take theappropriate action.

• Inversion of control in the extreme• Analogy with Maven: work with the framework, not against it.


Review: The Lifecycle Orchestrates MVCAdditional details added


Interacting with the Lifecycle

Phase Listeners – coarse grained

– Not aware of individual components

– act before and after each lifecycle phase

System Event– fine grained

– can be attached to an individual component instance

– act during each lifecycle phase

Phase Listeners and System Events



Similar in concept to Servlet Filter, but able to act within the JSF lifecycle

How to implement them– Provide an implementation of javax.faces.event.PhaseListener

– MethodExpression that takes a javax.faces.event.PhaseEvent

Phase Listeners


PhaseListener

public class MyPhaseListener implements PhaseListener {public PhaseId getPhaseId() {

return (PhaseId.ANY_PHASE);

}

public void afterPhase(PhaseEvent event) {

System.out.println("afterPhase(" + event.getPhaseId() + ")");

}

public void beforePhase(PhaseEvent event) {

System.out.println("beforePhase(" + event.getPhaseId() + ")");

}

}

Implementing the Interface javax.faces.event.PhaseListener


PhaseListener

For all pages: faces-config.xml

<lifecycle>

<phase-listener>standard.MyPhaseListener</phase-listener>

</lifecycle>

Per-page: <f:phaseListener> type attribute: fully qualified class name binding attribute: expression that evaluates to the instance

Declare to the Runtime


PhaseListener

FacesContext.renderResponse()– Skip to Render Response Phase

FacesContext.responseComplete()– Do no further lifecycle processing on this request.

How to impact the execution of the lifecycle



Publish/Subscribe event bus for things that happen during the JSF Lifecycle, not application specific

Inspired by Solaris Dtrace, Linux strace, truss, etc. Listeners can be registered at three scopes

– component UIComponent.subscribeToEvent()

– view UIViewRoot.subscribeToEvent()

– application Application.subscribeToEvent()

Publish is always with Application.publishEvent()

System Events


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1. Implement the listener interface

2. Register for the event– <f:event> tag

– faces-config.xml<application> <system-event-listener> <system-event-listener-class>com.foo.MyListener </system-event-listener-class> <system-event-class>javax.faces.event.PreRenderViewEvent </system-event-class> </system-event-listener></application>

System Events



How does JSF handle the concept of “value”?– Apply Request Values

unconverted string value pushed into UIComponent instances via decode() method

– Process Validations Value is converted with Converter and validated with Validator(s)

– Update Model Values Value is pushed to value expression (if any)

– Render Response Value is pulled from value expression

Type Safety for the UI



Behavior Based Interfaces– ValueHolder

Anything that displays a value

– EditableValueHolder When that value is editable by the end user.

Type Safety for the UI


ConverterStandard Converters in package javax.faces.Convert

Throw ConverterException to indicate conversion failure

Failure added as per-component FacesMessage, other components continue to be processed.

Skip to Render Response phase if one or more FacesMessage is present


Converter

public static class CustomConverter implements Converter {

public Object getAsObject(FacesContext context, UIComponent component, String value) {}

public String getAsString(FacesContext context, UIComponent component, Object value) {}

}

Implementing the interface javax.faces.convert.Converter


Converter

faces-config.xml– by id

<converter>

<converter-id>creditCardConverter</converter-id>

<converter-class>carstore.CreditCardConverter</converter-class>

</converter>

– by type <converter>

<converter-for-class>java.util.Date</converter-for-class>

<converter-class>com.mycompany.MyThirdConverter</converter-class>

</converter>



Converter

@FacesConverter annotation– value attribute is the converter id

– forClass attribute is the class converted by this converter

Important subtlety– Due to the nature of annotation scanning, a single usage of @FacesConverter may only have one or the other of value and forClass.



Associating a Converter with a UIComponent

Implicit converter, based on the type of the property referenced by the EL Expression

Explicit converter– <f:converter>

converterId attribute binding attribute

– converter attribute on a UIComponent

Subtlety with <h:selectManyListbox>– Must use <f:converter> for all types not handled by package javax.faces.convert converters

Several ways


Associating a Converter with a UIComponent

Programmatically: call ValueHolder.setConverter( )

Several ways


Validators

Throw ValidatorException to indicate validation failure

Failure added as per-component FacesMessage, other components continue to be processed.

Skip to Render Response phase if one or more FacesMessage is present

Standard Validators in package javax.faces.validator


Validators

public class CustomValidator1 implements Validator {

public void validate(FacesContext context, UIComponent component, Object value) throws ValidatorException {

}

}

Why the checked exception?– Validation is a business level concern, make it more explicit

Implementing the interface javax.faces.validator.Validator


ValidatorsTip

When programming custom Validators and Converters, program defensively.

Check inbound arguments for null. Avoid throwing non-expected exceptions


Validators

faces-config.xml<validator>

<validator-id>CreditCardValidator</validator-id>

<validator-class>com.foo.CreditCardValidator</validator-class>

</validator>

@FacesValidator annotation– value attribute is the id

– isDefault is boolean

Declaring a Validator to the runtime


Validators

Context parameter javax.faces.INTERPRET_EMPTY_STRING_SUBMITTED_VALUES_AS_NULL

– true: if the incoming value is the empty string, will automatically call UIInput.setSubmittedValue(null)

– false or not set: Allow the empty string to pass through

Empty String Considerations


Validators

Added to all EditableValueHolder instances in every page Declared in faces-config.xml<application>

<default-validators>

<validator-id>MyValidator</validator-id>

</default-validators>

<application/>

Empty <default-validators/> causes the list to be cleared Declared with @FacesValidator annotation isDefault attribute

Default Validator


Validators

The javax.faces.validate.BeanValidator validator is the default default Validator

It is the gateway to JSR-303 Bean Validation Validates the JavaBeans property referenced by the component Validation expressed as “constraint” annotation on the property Property vs whole bean validation

Bean Validator


ValidatorsBean Validator Standard Constraints

@NotNull(groups = Order.class)

@Size(min = 1, message = "{validator.notEmpty}", groups = Order.class)

@CreditCard(groups = Order.class)

public String getCreditCard() {

return creditCard;

}


Bean Validator

1. Annotate your annotation@Documented@Constraint(validatedBy = CreditCardConstraintValidator.class)@Target({ElementType.METHOD, ElementType.FIELD})@Retention(RetentionPolicy.RUNTIME)public @interface CreditCard {// message string should be {constraint.creditCard}String message() default "{validator.creditCard}”;//CreditCardVendor vendor default ANY;Class<?>[] groups() default {};Class<? extends Payload>[] payload() default {};}

Making your own constraints


Bean Validator

2. Implement your constraintpublic class CreditCardConstraintValidatorimplements ConstraintValidator<CreditCard, String> {private Pattern basicSyntaxPattern;public void initialize(CreditCard parameters) { basicSyntaxPattern = Pattern.compile("^[0-9\\ \\-]*$");}public boolean isValid(String value, ConstraintValidatorContext ctxt) {if (value == null || value.length() == 0) {return true;}if (!basicSyntaxPattern.matcher(value).matches()) { return false;} return luhnCheck(stripNonDigits(value));}}

Making your own constraints


Bean Validator

Context paramjavax.faces.validator.DISABLE_BEAN_VALIDATOR set to true

Disabling Bean Validator


Bean Validator

Basic Bean Validator Version 1.1 Method

and Parameter Validation

DEMOs


Bean Validator

Groups

Validates all but this one

Validates these only

Groups

Exposed to JSF via <f:validateBean validationGroups=“”>


Associating a Validator with a UIComponent

Nest validator tag inside component Programmatically, call EditableValueHolder.addValidator( )

Several ways


JSF Navigation Review


How to Declare Navigation

Explicit Navigation– Declared via XML rules in faces-

config.xml file

Implicit Navigation– Relies on filename of pages

– No need for rules in faces-config.xml


Explicit Navigation

Designed to be well suited to developer tools, hence syntax is verbose

“action” is returned from all ActionSource components

– Explicitly hard coded in the page

– Returned via a Value Expression


Implicit Navigation

from-view-id is the current view If there exists a page that is equivalent to the value of the current

action, the navigation is performed.

A reaction to all that verbosity


How Navigation Is Performed

JSF 1.0– All navigation was POSTback based

form does HTTP POST server does RequestDispatcher.forward() sends back new page, from old URL ABUSE OF HTTP!

JSF 2.0– Adds POST REDIRECT GET

POST vs GET


Further Navigation Enhancements

JSF 1.0– All navigation was POSTback based

form does HTTP POST server does RequestDispatcher.forward() sends back new page, from old URL ABUSE OF HTTP!

JSF 2.0– Adds POST REDIRECT GET

JSF 2.2 Faces Flows


What’s in a Flow? Flow Nodes

Further Navigation Enhancements JSF 2.2 Faces Flows


PDF 7.5.1

Further Navigation Enhancements JSF 2.2 Faces Flows


Questions?

Ed Burns@edburns


The preceding is intended to outline our general product direction. It is intended for information purposes only, and may not be incorporated into any contract.It is not a commitment to deliver any material, code, or functionality, and should not be relied upon in making purchasing decisions. The development, release, and timing of any features or functionality described for Oracle’s products remains at the sole discretion of Oracle.

Best Practices for JSF, Gameduell 2013

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