Declarative input validation with JSR 303 and ExtVal

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Declarative input validationwith JSR 303 and ExtVal

BART KUMMEL

BKUMMEL@TRANSFER-SOLUTIONS.COM

3 NOVEMBER 2010

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Who am I?

Bart KummelNearly 10 years experience in software development

Of which 5 years in Java EE

Consultant @ Transfer SolutionsCompetence Manager Java EE @ Transfer SolutionsAuthor of Apache MyFaces 1.2 Web Application Development

See http://tinyurl.com/am12wad

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Don’t Repeat Yourself

Less code = less bugs

Duplicated code = duplicated bugs

Duplicated code = duplicated maintenance

Dupliacted maintenance = forgotten maintenance

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DRY violations in classic Java EE apps

Validation is programmed in Model beansBecause that’s where it belongs

Validation is repeated in View layerBecause you have to use JSF Validators

Validation is even repeated multiple times in the ViewBecause the same bean is used in multiple JSF pages

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Remove validation code from ViewLet View generate validation based on Model

Let’s fix this

How to fix it?

That’s why Bean Validation (JSR 303) was created

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JSR 303: the idea

Standardized way to express validation constraints

Any UI technology can interpret those constraints and enforce them

Non-UI technologies can also use the validation information

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JSR 303: the idea implemented

JSR 303 is part of Java EE 6The reference implementation is Hibernate Validator 4.*

See http://hibernate.org/subprojects/validator.htmlHibernate Validator 4.* can also be used in Java EE 5

A JSR 303 implementation is only the way to express the validation constraints

You don’t get UI validation logic if the UI framework doesn’t support JSR 303

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Bean Validation in Java EE 5

Add Hibernate Validator 4.* as library...and some extra libraries, provided in the Hibernate Validator package

Use JSR 303 annotations in your beans

Use MyFaces ExtVal 1.2.* to add declarative validation support to JSF 1.2

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Bean Validation in Java EE 6

No need to add a JSR 303 implementationJSR 303 is part of the Java EE 6 platform

Use JSR 303 annotations in your beansJSF 2.0 has support for JSR 303 annotations out of the box

But support is limited

You can (and should!) still use ExtVal (2.0.*) and get lots of benefits (more on that later)

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Side note: ExtVal versioning

There are three current versions of ExtVal1.1.* for JSF 1.11.2.* for JSF 1.22.0.* for JSF 2.0

The latest stable release is release 3That is: 1.1.3, 1.2.3 and 2.0.3

Lots of exciting new stuff is going into the next version

Snapshot releases of ExtVal are very high quality

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Example: classic validation code in bean

@Min(0)@Max(100000)

private int capacity;

public void setCapacity(int capacity) { if(capacity >= 0 && capacity <= 100000) { this.capacity = capacity; } else { // throw exception }

}

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Example: JSR 303 annotations

@Min(0)@Max(100000)

private int capacity;

public void setCapacity(int capacity) { this.capacity = capacity;}

Extra benefits:

– less code

– better readable

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Example: classic validation in JSF page

<h:inputText value="#{room.capacity}" > <f:validateLongRange minimum = "0" maximum = "100000" /></h:inputText>

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Example: no validation in JSF page!

<h:inputText value="#{room.capacity}" />

Benefits:

– less code

– DRY!

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Demo 1: Bean Validation basics in Java EE 6

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So why do we need ExtVal?

To use Bean Validation in Java EE 5 / JSF 1.2

To have advanced options in Java EE 6

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ExtVal on Java EE 6: advanced options

Cross validationViolation severity

i.o.w. give warnings instead of errors

More flexibility in choice of annotations to useJSR 303, JPA, ExtVal, own annotation or any combination

Customization on all levels, e.g.:Custom message resolversCustom validation strategiesCustom meta data

demos coming up!

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Configuring ExtVal

Just add the ExtVal .jar files to your project

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Demo 2: Adding the ExtVal .jar files to our project

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Cross validation

Examples of cross validationcheck if two values are equalcheck if date is before or after other datevalue is only required if other value is empty (or not)etcetera...

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Demo 3: Cross validation

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Demo 3 – Summary

@DateIs can be used for date-related cross validations

Use DateIsType.before, DateIsType.after or DateIsType.same

Other cross validation annotations:@Equals and @NotEquals for equality-based cross validation of any type@RequiredIf for conditional required fields

Use RequiredIfType.empty or RequiredIfType.not_empty

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Violation severity

Give certain validation rules a severity level of “warning”

A warning will be given to the user, but “invalid” data can be submitted

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Demo 4: Setting violation severity to “warning”

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Demo 4 – summary

Violation severity is not part of the JSR 303 standardWe use payload to add violation severity level as custom meta data

JPA also interprets JSR 303 contraints before persisting data, but does not recognise violation severity

Solution: use ExtVal annotations instead

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Customization on all levels

ExtVal is full of customization hooks

A lot of ready-made add-ons are availablesee http://os890.blogspot.com

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Demo 5: Creating a custom annotation and a custom validation strategy

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Demo 5 – summary

Technically, creating a custom annotation is not an ExtVal feature

It is just a Java feature

We need an ExtVal validation strategy to make a custom annotation workWe need to map our annotation to our validation strategy

We can create a startup listener for thisAs an alternative we can use ExtVal plugins to use alternative ways of configuration

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Summary

With annotation based valition, we can finally create DRY JSF applicationsExtVal gives us the opportunity to use annotation-based validation on Java EE 5 On Java EE 6, ExtVal gives us:

More powerful annotation-based validationMore flexibility

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More info...

I will put links to slides & demo code on my blog http://www.bartkummel.net

Chapter 10 of MyFaces 1.2 Web Application Development

http://tinyurl.com/am12wad

MyFaces ExtVal: http://myfaces.apache.org/extensions/validatorhttp://os890.blogspot.com/

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