JSR-303 Bean Validation API

JSR-303 Bean Validation API

•
Overview
•
Concept
•
Defining Constraints
•
Validate Constraints
•
Bootstrapping
•
Integration JEE/JSF

Heiko Scherrer

Preface JSR-303

•
Specifies common validation concept for
JavaBeans™
•
For JavaEE & SE, extension of the
JavaBeans object model
•
JSR-303 addresses validation in all
layers of the application

Heiko Scherrer

Before JSR-303

DDL: CHECK(length(email)==8)
Script:if (email.length == 8) {...}

if (email.length() == 8) {...}
Person {
<f:validateLength minimum="8" /> …
@Column(length=8)
String email;
…
}

Heiko Scherrer

Without Specification

•
Several validation frameworks exist:
●
Apache Common-Validator
●
Hibernate Validator
●
JSF Validators
●
...
•
Not all frameworks for all layers
=>Duplicated error-prone code
=>Similar to JPA: A standard is needed!

Heiko Scherrer

With JSR-303

Constraint is
validated in
all layers!

Person {
…
@Min(8)
String email;
…
}

Heiko Scherrer

JSR-303 - Concept

•
The JSR-303 API guarantees a stable,
independent and extensible way to
define constraints in domain objects and
validate them
•
At least two implementations (SPI) are
currently available: Hibernate, Spring3

Heiko Scherrer

JSR-303 - Concept
Specifies responsibilities
of the implementation: Validation.buildDefaultValidatorFactory()
Exceptions, Factories...

Interesting parts
Validator definition:
Standard constraint Specifies how to
Definitions: validate data
@NotNull, @Min ...
validator.validate(myClass)

Heiko Scherrer

JSR-303 – Standard Constraints

Name Description
@NotNull must not be NULL
@AssertTrue must not be true. NULL means valid
@AssertFalse must not be false. NULL means valid
@Min must be a number whose value must be higher or equal
@Max must be a number whose value must be lower or equal
@DecimalMin same as @Min
@DecimalMax same as @Max
@Size must been between the specified boundaries (included)
@Digits must be a number within accepted range (included)
@Past must be a date in the past
@Future must be a date in the future
@Pattern must match the defined regular expression

Heiko Scherrer

JSR-303 – Constraints

•
Constraints can be defined on methods, fields,
annotations (constructors and parameters)
•
Custom constraints: @Constraint (see
sourcecode example)
•
Constraints have properties: message,
payload, groups
•
Annotated methods must follow the
JavaBeans™ specification

Heiko Scherrer

JSR-303 – Constraints II

•
Validation of two separate properties is done
within a validation method
•
A validation method is annotated with a
Constraint and must follow JavaBeans Spec.

@AssertTrue
public boolean isValid() {
…
return qty1 > qty2;
}

Heiko Scherrer

JSR-303 – Constraint example

•
Custom constraints can validate multiple fields
•
Some constraints apply to the database schema
•
Constraints can be grouped together using the groups
property
•
The message text is interpolated ({…}) and
internationalized
Custom
constraint

Grouped
together

Simple
constraint in
default group

Added a
message text

Heiko Scherrer

JSR-303 – Grouping constraints

•
Not all declared constraints Define a group:
/**
shall be validated each time * A PersistenceGroup
* validation group. This group
•
Different layers use perhaps a * is validated in the integration layer.
*/
different sequence of public interface PersistenceGroup { }
validation
•
Simple Java marker interfaces In your domain class:
(also classes) are used for @NotNull(groups = PersistenceGroup.class)
private String businessKey;
grouping
•
Group inheritance with class Validate the group:
inheritance validator.validate(obj, PersistenceGroup.class);

•
Constraints on @Constraints Bring all groups in a defined order:
allows composing them @GroupSequence(
{Default.class, WMChecks.class,
PersistenceGroup.class})
•
Sequencing is done with public interface SequencedChecks {
@GroupSequence }

Heiko Scherrer

JSR-303 - Validation

•
Similar to JPA the Bean Validation API defines
a factory to create a Validator
•
Validation is done with a Validator instance
•
Three methods at all:
● validate(T object, Class<?>... groups)
● validateProperty(T object,String pName, Class<?>... groups)
● validateValue(Class<T> clazz, String pName, Object val, Class<?>... groups)

•
The return value is an empty Set in case the
validation succeeds

Heiko Scherrer

JSR-303 – Validation (II)

•
ConstraintViolation in case of failure
•
to determine the reason why use methods like:
●
String getMessage();
●
Object getInvalidValue();
•
ValidationMessages.properties file for custom messages
•
@NotNull(message=”{org.openwms.resources.myText}”

Set<ConstraintViolation<MyClass>> c = validator.validate(obj);
assertEquals(1, c.size());

assertEquals("text defined with the constraint", c.iterator().next().getMessage());

assertEquals(2, validator.validate(obj, PersistenceGroup.class).size());

assertEquals(0, validator.validateProperty(obj, "qtyOnHand").size());

Heiko Scherrer

JSR-303 – Bootstrapping in J2SE

•
In a J2SE environment as well as JUnit test
classes the factory/validator is instanciated:
● ValidatorFactory f = Validation.buildDefaultValidatorFactory();
Validator validator = factory.getValidator();

•
The ValidatorFactory is thread-safe,
creation is an expensive operation
●
This is done in a static method in the test super
class
•
Creating the Validator is fast and can be
done in each test execution method

Heiko Scherrer

JSR-303 – Bootstrapping in JEE6

•
In an EJB container it is not allowed to call the
static build method
•
The factory and the validator are handled as
Resources
•
In an EJB container use:
● @Resource ValidatorFactory factory;
@Resource Validator validator;

•
Or JNDI to lookup both:
● initCtx.lookup("java:comp/ValidatorFactory");
initCtx.lookup("java:comp/Validator");

•
JEE5 does not implement the Bean Val. SPI!

Heiko Scherrer

JSR-303 – Activation in JEE6/JPA

•
JPA2.0 comes along with built-in validation
support with JSR-303
•
Persistence.xml defines a new element:
<validation-mode>
● AUTO: Validation is done before create/update/delete
if Validation provider is present
● CALLBACK: An exception is raised when no Validator
is present
● NONE: Bean Validation is not used at all

Heiko Scherrer

JSR-303 – Usage in JSF2.0

•
Outside JEE6 use the servlet context param:
● javax.faces.validator.beanValidator.ValidatorFactory
●
Without this param the classpath is scanned
•
Within JEE6 use annotations or access the
ServletContext. The container is responsible
to make the factory available there
•
Validation can be done programatically or
declarative
●
<h:inputText value=”#{myBean.name}”>
<f:validateBean />
</h:inputText>

Heiko Scherrer

Recommended links

•
JSR-303 final specification
•
JSR-314 JSF2.0 final specification
•
JSR-316 JEE6 final specification
•
Hibernate Validator documentation

Heiko Scherrer

JSR-303 Bean Validation API

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