JunMystery Bean Validation Cheat Sheet
Introduction
This article is focused on providing clear, simple, actionable guidance for providing Java Bean Validation security functionality in your applications.
Bean validation (aka Jakarta Validation) is one of the most common ways to perform input validation in Java. It is an application layer agnostic validation spec which provides the developer with the means to define a set of validation constraints on a domain model and then perform validation of those constraints through out the various application tiers.
One advantage of this approach is that the validation constraints and the corresponding validators are only written once, thus reducing duplication of effort and ensuring uniformity:
Typical Validation
Bean Validation
Setup
The examples in this guide use Hibernate Validator.
Add Hibernate Validator to your pom.xml:
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-validator</artifactId>
<version>USE_LATEST_VERSION</version>
</dependency>
Enable bean validation support in Spring's context.xml:
<beans:beans ...
...
<mvc:annotation-driven />
...
</beans:beans>
For more info, please see the setup guide
Basics
In order to get started using Bean Validation, you must add validation constraints (@Pattern, @Digits, @Min, @Max, @Size, @Past, @Future, @CreditCardNumber, @Email, @URL, etc.) to your model and then utilize the @Valid annotation when passing your model around in various application layers.
Constraints can be applied in several places:
- Fields
- Properties
- Classes
For Bean Validation 1.1 also on:
- Parameters
- Return values
- Constructors
For the sake of simplicity all the examples below feature field constraints and all validation is triggered by the controller. Refer to the Bean Validation documentation for a full list of examples.
When it comes to error handling, the Hibernate Validator returns a BindingResult object which contains a List<ObjectError>. The examples below feature simplistic error handling, while a production ready application would have a more elaborate design that takes care of logging and error page redirection.
Predefined Constraints
@Pattern
Annotation:
@Pattern(regex=,flag=)
Data Type:
CharSequence
Use:
Checks if the annotated string matches the regular expression regex considering the given flag match. Please visit OWASP Validation Regex Repository for other useful regex's.
Reference:
Model:
import org.hibernate.validator.constraints.Pattern;
public class Article {
//Constraint: Alpha Numeric article titles only using a regular expression
@Pattern(regexp = "[a-zA-Z0-9 ]")
private String articleTitle;
public String getArticleTitle() {
return articleTitle;
}
public void setArticleTitle(String articleTitle) {
this.articleTitle = articleTitle;
}
...
}
Controller:
import javax.validation.Valid;
import com.company.app.model.Article;
@Controller
public class ArticleController {
...
@RequestMapping(value = "/postArticle", method = RequestMethod.POST)
public @ResponseBody String postArticle(@Valid Article article, BindingResult result,
HttpServletResponse response) {
if (result.hasErrors()) {
String errorMessage = "";
response.setStatus(HttpServletResponse.SC_BAD_REQUEST);
List<ObjectError> errors = result.getAllErrors();
for(ObjectError e : errors) {
errorMessage += "ERROR: " + e.getDefaultMessage();
}
return errorMessage;
} else {
return "Validation Successful";
}
}
}
@Digits
Annotation:
@Digits(integer=,fraction=)
Data Type:
BigDecimal, BigInteger, CharSequence, byte, short, int, long and the respective wrappers of the primitive types; Additionally supported by HV: any sub-type of Number
Use:
Checks whether the annotated value is a number having up to integer digits and fraction fractional digits
Reference:
Model:
import org.hibernate.validator.constraints.Digits;
public class Customer {
//Constraint: Age can only be 3 digits long or less
@Digits(integer = 3, fraction = 0)
private int age;
public String getAge() {
return age;
}
public void setAge(String age) {
this.age = age;
}
...
}
Controller:
import javax.validation.Valid;
import com.company.app.model.Customer;
@Controller
public class CustomerController {
...
@RequestMapping(value = "/registerCustomer", method = RequestMethod.POST)
public @ResponseBody String registerCustomer(@Valid Customer customer, BindingResult result,
HttpServletResponse response) {
if (result.hasErrors()) {
String errorMessage = "";
response.setStatus(HttpServletResponse.SC_BAD_REQUEST);
List<ObjectError> errors = result.getAllErrors();
for( ObjectError e : errors) {
errorMessage += "ERROR: " + e.getDefaultMessage();
}
return errorMessage;
} else {
return "Validation Successful";
}
}
}
@Size
Annotation:
@Size(min=, max=)
Data Type:
CharSequence, Collection, Map and Arrays
Use:
Checks if the annotated element's size is between min and max (inclusive)
Reference:
Model:
import org.hibernate.validator.constraints.Size;
public class Message {
//Constraint: Message must be at least 10 characters long, but less than 500
@Size(min = 10, max = 500)
private String message;
public String getMessage() {
return message;
}
public void setMessage(String message) {
this.message = message;
}
...
}
Controller:
import javax.validation.Valid;
import com.company.app.model.Message;
@Controller
public class MessageController {
...
@RequestMapping(value="/sendMessage", method=RequestMethod.POST)
public @ResponseBody String sendMessage(@Valid Message message, BindingResult result,
HttpServletResponse response){
if(result.hasErrors()){
String errorMessage = "";
response.setStatus(HttpServletResponse.SC_BAD_REQUEST);
List<ObjectError> errors = result.getAllErrors();
for( ObjectError e : errors){
errorMessage+= "ERROR: " + e.getDefaultMessage();
}
return errorMessage;
}
else{
return "Validation Successful";
}
}
}
@Past / @Future
Annotation:
@Past, @Future
Data Type:
java.util.Date, java.util.Calendar, java.time.chrono.ChronoZonedDateTime, java.time.Instant, java.time.OffsetDateTime
Use:
Checks whether the annotated date is in the past / future
Reference:
Model:
import org.hibernate.validator.constraints.Past;
import org.hibernate.validator.constraints.Future;
public class DoctorVisit {
//Constraint: Birthdate must be in the past
@Past
private Date birthDate;
public Date getBirthDate() {
return birthDate;
}
public void setBirthDate(Date birthDate) {
this.birthDate = birthDate;
}
//Constraint: Schedule visit date must be in the future
@Future
private String scheduledVisitDate;
public String getScheduledVisitDate() {
return scheduledVisitDate;
}
public void setScheduledVisitDate(String scheduledVisitDate) {
this.scheduledVisitDate = scheduledVisitDate;
}
...
}
Controller:
import javax.validation.Valid;
import com.company.app.model.DoctorVisit;
@Controller
public class DoctorVisitController {
...
@RequestMapping(value="/scheduleVisit", method=RequestMethod.POST)
public @ResponseBody String scheduleVisit(@Valid DoctorVisit doctorvisit, BindingResult result,
HttpServletResponse response){
if(result.hasErrors()){
String errorMessage = "";
response.setStatus(HttpServletResponse.SC_BAD_REQUEST);
List<ObjectError> errors = result.getAllErrors();
for( ObjectError e : errors){
errorMessage+= "ERROR: " + e.getDefaultMessage();
}
return errorMessage;
}
else{
return "Validation Successful";
}
}
}
Combining Constraints
Validation annotations can be combined in any suitable way. For instance, to specify a valid reviewRating value between 1 and 5, specify the validation like this :
Annotation:
@Min(value=), @Max(value=)
Data Type:
BigDecimal, BigInteger, byte, short, int, long and the respective wrappers of the primitive types; Additionally supported by HV: any sub-type of CharSequence (the numeric value represented by the character sequence is evaluated), any sub-type of Number
Use:
Checks whether the annotated value is higher/lower than or equal to the specified minimum
Reference:
Model:
import org.hibernate.validator.constraints.Min;
import org.hibernate.validator.constraints.Max;
public class Review {
//Constraint: Review rating must be between 1 and 5
@Min(1)
@Max(5)
private int reviewRating;
public int getReviewRating() {
return reviewRating;
}
public void setReviewRating(int reviewRating) {
this.reviewRating = reviewRating;
}
...
}
Controller:
import javax.validation.Valid;
import com.company.app.model.ReviewRating;
@Controller
public class ReviewController {
...
@RequestMapping(value="/postReview", method=RequestMethod.POST)
public @ResponseBody String postReview(@Valid Review review, BindingResult result,
HttpServletResponse response){
if(result.hasErrors()){
String errorMessage = "";
response.setStatus(HttpServletResponse.SC_BAD_REQUEST);
List<ObjectError> errors = result.getAllErrors();
for( ObjectError e : errors){
errorMessage+= "ERROR: " + e.getDefaultMessage();
}
return errorMessage;
}
else{
return "Validation Successful";
}
}
}
Cascading Constraints
Validating one bean is a good start, but often, beans are nested or in a complete graph of beans. To validate that graph in one go, apply cascading validation with @Valid
Additional Constraints
In addition to providing the complete set of JSR303 constraints, Hibernate Validator also defines some additional constraints for convenience:
@CreditCardNumber@EAN@Email@Length@Range@ScriptAssert@URL
Take a look at this list for the complete list.
Note that @SafeHtml, a previously valid constraint, has been deprecated according to the Hibernate Validator 6.1.0.Final and 6.0.18.Final release blogpost. Please refrain from using the @SafeHtml constraint.
Custom Constraints
One of the most powerful features of bean validation is the ability to define your own constraints that go beyond the simple validation offered by built-in constraints.
Creating custom constraints is beyond the scope of this guide. Please see this documentation.
Error Messages
It is possible to specify a message ID with the validation annotation, so that error messages are customized :
@Pattern(regexp = "[a-zA-Z0-9 ]", message="article.title.error")
private String articleTitle;
Spring MVC will then look up a message with ID article.title.error in a defined MessageSource. More on this documentation.