DMIT221
Bean Validation
with Hibernate
Validator
Learning Objectives
• Upon completion of this lesson, you will be able to:
– Use bean validation annotations
– Test bean validation annotations
Validating Data
• Common data validation tasks:
– Required field validation
– Compare validation
– Range validation (numeric range, date range, string
length range)
– Regular Expression validation (email address, phone
number, postal code)
Custom Validation
• With a layered application, validating data is a common task
that is often duplicated in each layer, proving time consuming
and error-prone
DRY Principle
• Don’t Repeat Yourself(DRY)
• “Every piece of knowledge must have a single,
unambiguous, authoritative representation within a system”
Domain Model Validation
• To avoid duplication of validation code, the validation logic
can be bundle directly into the domain model
Bean Validation Specification
(JSR 303)
• Bean Validation Specification defines a metadata model and
API for entity validation
• Bean Validation Specification API is not tied to a specific
application tier or programming model, and is available for
both server-side and client-side application programming
• Hibernate Validator is the reference implementation for the
Bean Validation Specification
• Apache Bean Validation is another implementation of the
Bean Validation Specification
Defining Constraints (1)
• Constraints are expressed via Java annotations
• Three different type of constraint annotations
1. Field-level constraints
2. Property-level constraints
3. Class-level constraints
• The type of constraint annotation is determined by the
location of the annotation
• Field-level and property-level constraints do the same thing
so use either field or property annotation within one class
but not both
Defining Constraints (2)
• Class-level constraints are used when there is a need to:
1. Inspect more than a single property of the class to
validate it
2. Evaluate the correlation between different state
variables
Example: field-level constraints
import javax.validation.constraints.*;
public class Car {
@NotNull
private String manufacturer;
@AssertTrue
private boolean isRegistered;
public Car(String manufacturer, boolean isRegistered) {
this.manufacturer = manufacturer;
this.isRegistered = isRegistered;
}
// getters and setters …
}
Example: property-level constraints
import javax.validation.constraints.*;
public class Car {
private String manufacturer;
private boolean isRegistered;
public Car(String manufacturer, boolean isRegistered) {
this.manufacturer = manufacturer;
this.isRegistered = isRegistered;
}
@NotNull
public String getManufacturer() {
return manufacturer;
}
public void setManufacturer(String manufacturer) {
this.manufacturer = manufacturer;
}
@AssertTrue
public boolean isRegistered() {
return isRegistered;
}
public void setRegistered(boolean isRegistered) {
this.isRegistered = isRegistered;
}
}
Example: class-level constraints
import javax.validation.constraints.*;
@PassengerCount
public class Car {
@NotNull
private String manufacturer;
@NotNull
@Size(min = 2, max = 14)
private String licensePlate;
@Min(2)
private int seatCount;
private List<Person> passengers;
public Car(String manufacturer, String licencePlate, int seatCount) {
this.manufacturer = manufacturer;
this.licensePlate = licencePlate;
this.seatCount = seatCount;
}
//getters and setters ...
}
Validating Constraints
1. Obtain a Validator instance
javax.validation.ValidatorFactory factory = javax.validation.V
alidation.buildDefaultValidatorFactory();
javax.validation.Validator validator = factory.getValidator();
2. Use one of the three validator methods to validate either
entire entities or just a single property of the entity
1. validate() method – use to perform validation of all
constraints of a given entity instance
2. validateProperty() method – use to perform validation
on a single named property of a given object
3. validateValue() method – use to check whether a single
property of a given class can be validated successfully, if the
property had the specified value
Example: Validator.validate() method
ValidatorFactory factory
= Validation.buildDefaultValidatorFactory();
Validator validator = factory.getValidator();
Car car = new Car(null);
Set<ConstraintViolation<Car>> constraintViolations
= validator.validate(car);
assertEquals(1, constraintViolations.size());
assertEquals("may not be null",
constraintViolations.iterator().next().getMessage());
Example: Validator.validateProperty()
method
Validator validator
= Validation.buildDefaultValidatorFactory().getValidator();
Car car = new Car(null);
Set<ConstraintViolation<Car>> constraintViolations
= validator.validateProperty(car, "manufacturer");
assertEquals(1, constraintViolations.size());
assertEquals("may not be null",
constraintViolations.iterator().next().getMessage());
Example: Validator.validateValue() method
Validator validator
= Validation.buildDefaultValidatorFactory().getValidator();
Set<ConstraintViolation<Car>> constraintViolations
= validator.validateValue(Car.class, "manufacturer", null);
assertEquals(1, constraintViolations.size());
assertEquals("may not be null",
constraintViolations.iterator().next().getMessage());
Adding Capabilities To Use
Third-Party Libraries
• To use a third-party library you can either
– Add the library files to the CLASSPATH environment
variable of the operating system
– For an Eclipse you can add the library files to the Java
Build Path project property
– For web applications you can copy the library files to
"WEB-INF/lib" directory of the web application
• The CLASSPATH environment variable tells SDK tools and
applications where to find third-party and user-defined
classes
• The Java Build Path property of a project tells Eclipse
where to find third-party and user-defined classes
Download and Install
Hibernate Validator 4.2.0.Final
1.
2.
•
•
Download Hibernate Validator 4.2.0.Final
From a Terminal session type:
su
unzip /home/dmit/Downloads/hibernate-validator4.2.0.Final-dist.zip –d /opt/dmit221sdk
Adding Hibernate Validator
Capabilities
• Add the following library files from the "
/opt/dmit221sdk/hibernate-validator-4.2.0.Final"
directory to the Java Build Path property of your Eclipse
project:
– hibernate-validator-4.2.0.Final.jar
– hibernate-validator-annotation-processor4.2.0.Final.jar
– lib/required/validaton-api-1.0.0.GA.jar
– lib/required/slf4j-api-1.6.1.jar
– lib/optional/log4j-1.2.16.jar
– lib/optional/slf4j-log4j12-1.6.1.jar
Bean Validation Constraints (1)
Annotation
Use
Example
@AssertFalse
The value of the field or property must be
false.
@AssertFalse
boolean isUnsupported;
@AssertTrue
The value of the field or property must be
true.
@AssertTrue
boolean isActive;
@DecimalMax
The value of the field or property must be a
decimal value less than or equal to the
number in the value element
@DecimalMax(value="99.99")
double wage;
@DecimalMin
The value of the field or property must be
greater than or equal to the number in the
value element
@DecimalMin(value="8.88")
double wage;
Bean Validation Constraints (2)
Annotatio
n
Use
Example
@Digits(
integer=,
fraction=)
The value of the field or property must be a
number within a specific range. The integer
element specifies the maximum integral digits
for the number, and the fraction element
specifies the maximum fractional digits for the
number
@Digits(integer=6,faction=2)
double price;
@Future
Date must be in the future
@Future
Date eventDate;
Bean Validation Constraints (3)
Annotation
Use
Example
@Max
The value of the field or property must be an integer
value less than or equal to the number in the value
element.
@Max(value=25)
int quantity;
@Min
The value of the field or property must be an integer
value greater than or equal to the number in the value
element.
@Min(value=5)
int quantity;
@NotNull
The value of the field or property must not be null.
@NotNull
String username;
@Null
The value of the field or property must be null.
@Null
String oldName;
Bean Validation Constraints (4)
Annotation
Use
Example
@Past
The value of the field or property must be a
date in the past.
@Past
Date birthday;
@Pattern
The value of the field or property must match
the regular expression defined in the regexp
element.
@Pattern(regexp=
"^.+@.+\\.[a-zA-Z]{2,4}$")
String emailAddress;
@Size(min=,
max=)
The size of the field or property is evaluated
and must match the specified boundaries.
@Size(min=5,max=25)
String username;
@Valid
Perform validation recursively on the
associated object.
@Valid
Category productCategory;
Hibernate Constraints Extensions
Annotation
Use
@CreditCardNumber
String passes the Luhn checksum test
@Email
String must a valid email address
@Length(min=,max=)
String length is between min and max. Hibernate
column constraint metadata added
@NotBlank
Trimmed string length must be greater than 0
@NotEmpty
String is not null and is not empty
@Range(min=,max=)
Numeric value must be between min and max
@URL(protocol=,host=,port=
)
String must be a valid URL
Review Questions
•
•
•
•
What is the main reason for using the Bean Validation?
Name the three level of constraints
Name the three methods used for validation
Which annotation is use to check for a minimum integer
value?
• Which annotation is use to check if a string matches a
regular expression pattern?
• Which annotation is use to check the number of elements in
a collection?
• Is the @Past or @Future annotation inclusive?
Resources
• Hibernate Validator Reference Guide
• JSR 303: Bean Validation
DO NOW
Exercise 13