Slides of my talk at the CONFESS_2011 conference in Vienna, Austria

1. Declarative input validation
with JSR 303 and ExtVal
April 13th, 2011 – Bart Kummel

2. Who am I?
● Bart Kummel
● 10 years experience
in software development
● Of which 6 years in Java EE
● Consultant @ Transfer Solutions,
Leerdam, NL
● Competence manager @
Transfer Solutions, Leerdam, NL
● Author of Apache MyFaces 1.2
Web Application Development
● See http://tinyurl.com/am12wad
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3. Photo: Salar de Uyuni, Bolivia; © 2010 by Bart Kummel 3

4. Don’t Repeat Yourself
● Less code = less bugs
● Duplicated code = duplicated bugs
● Duplicated code = duplicated maintenance
● Dupliacted maintenance = forgotten maintenance
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5. DRY violations in classic Java EE apps
● Validation is programmed in Model beans
● Because that’s where it belongs
● Validation is repeated in View layer
● Because you have to use JSF Validators
● Validation is even repeated multiple times in the View
● Because the same bean is used in multiple JSF pages
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6. Let’s fix this
● Remove validation code from View
● Let View generate validation based on Model
How to fix it?
● That’s why Bean Validation (JSR 303) was created
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7. 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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8. JSR 303: the idea implemented
● JSR 303 is part of Java EE 6
● The reference implementation is
Hibernate Validator 4.*
● See http://hibernate.org/subprojects/validator.html
● Hibernate 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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9. How to add Bean Validation to a Java EE 5 application
● 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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10. Bean Validation in Java EE 6
● No need to add a JSR 303 implementation
● JSR 303 is part of the Java EE 6 platform
● Use JSR 303 annotations in your beans
● JSF 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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11. Side note: ExtVal versioning
● There are three current versions of ExtVal
● 1.1.* for JSF 1.1
● 1.2.* for JSF 1.2
● 2.0.* for JSF 2.0
● The latest stable release is release 3
● That 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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12. Example: classic validation code in bean
private int capacity;
public void setCapacity(int capacity) {
if(capacity >= 0 && capacity <= 100000) {
this.capacity = capacity;
} else {
// throw exception
}
}
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13. Example: JSR 303 annotations
@Min(0)
@Max(100000)
private int capacity;
public void setCapacity(int capacity) {
this.capacity = capacity;
}
enefits:
Extra b
– less code
eadable
– better r
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14. Example: classic validation in JSF page
<h:inputText value="#{room.capacity}" >
<f:validateLongRange minimum = "0"
maximum = "100000" />
</h:inputText>
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15. Example: no validation in JSF page!
<h:inputText value="#{room.capacity}" />
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16. Demo 1:
Bean Validation basics in Java EE 6

17. 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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18. ExtVal on Java EE 6: advanced options
● Cross validation
● Violation severity
● i.o.w. give warnings instead of errors
● More flexibility in choice of annotations to use
● JSR 303, JPA, ExtVal, own annotation or any combination
● Customization on all levels, e.g.:
● Custom message resolvers
● Custom validation strategies demos
Custom meta data
coming
●
up!
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19. Configuring ExtVal
● Just add the ExtVal .jar files to your project
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20. Demo 2:
Adding the ExtVal .jar files to our project

21. Cross validation
● Examples of cross validation
● check if two values are equal
● check if date is before or after other date
● value is only required if other value is empty (or not)
● etcetera...
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22. Demo 3:
Cross validation

23. 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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24. 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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25. Demo 4:
Setting violation severity to “warning”

26. Demo 4 – summary
● Violation severity is not part of the JSR 303 standard
● We 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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27. Customization on all levels
● ExtVal is full of customization hooks
● A lot of ready-made add-ons are available
● see http://os890.blogspot.com
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28. Demo 5:
Creating a custom annotation and a
custom validation strategy

29. 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 work
● We need to map our annotation to our validation strategy
● We can create a startup listener for this
● As an alternative we can use ExtVal plugins to use alternative ways of
configuration
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30. Summary
● With annotation based validation, we can
finally create DRY JSF applications
● ExtVal gives us the opportunity to use
annotation-based validation on Java EE 5
● On Java EE 6, ExtVal gives us:
● More powerful annotation-based validation
● More flexibility
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31. More info...
● Workshop tomorrow: ‘Rule your model with Bean-Validation’
● 08:00 – 10:00, Room 2 – Gerhard Petracek
● 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/validator
● http://os890.blogspot.com/
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32. Questions & answers
A wise man can learn more from a
foolish question than a fool can learn
from a wise answer.
Bruce Lee
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