I would like to know what is the cleanest and best way to perform form validation of user inputs. I have seen some developers implement org.springframework.validation.Validator. A question about that: I saw it validates a class. Does the class have to be filled manually with the values from the user input, and then passed to the validator?
I am confused about the cleanest and best way to validate the user input. I know about the traditional method of using request.getParameter() and then manually checking for nulls, but I don't want to do all the validation in my Controller. Some good advice on this area will be greatly appreciated. I am not using Hibernate in this application.
With Spring MVC, there are 3 different ways to perform validation : using annotation, manually, or a mix of both. There is not a unique "cleanest and best way" to validate, but there is probably one that fits your project/problem/context better.
Let's have a User :
public class User {
private String name;
...
}
Method 1 : If you have Spring 3.x+ and simple validation to do, use javax.validation.constraints annotations (also known as JSR-303 annotations).
public class User {
#NotNull
private String name;
...
}
You will need a JSR-303 provider in your libraries, like Hibernate Validator who is the reference implementation (this library has nothing to do with databases and relational mapping, it just does validation :-).
Then in your controller you would have something like :
#RequestMapping(value="/user", method=RequestMethod.POST)
public createUser(Model model, #Valid #ModelAttribute("user") User user, BindingResult result){
if (result.hasErrors()){
// do something
}
else {
// do something else
}
}
Notice the #Valid : if the user happens to have a null name, result.hasErrors() will be true.
Method 2 : If you have complex validation (like big business validation logic, conditional validation across multiple fields, etc.), or for some reason you cannot use method 1, use manual validation. It is a good practice to separate the controller’s code from the validation logic. Don't create your validation class(es) from scratch, Spring provides a handy org.springframework.validation.Validator interface (since Spring 2).
So let's say you have
public class User {
private String name;
private Integer birthYear;
private User responsibleUser;
...
}
and you want to do some "complex" validation like : if the user's age is under 18, responsibleUser must not be null and responsibleUser's age must be over 21.
You will do something like this
public class UserValidator implements Validator {
#Override
public boolean supports(Class clazz) {
return User.class.equals(clazz);
}
#Override
public void validate(Object target, Errors errors) {
User user = (User) target;
if(user.getName() == null) {
errors.rejectValue("name", "your_error_code");
}
// do "complex" validation here
}
}
Then in your controller you would have :
#RequestMapping(value="/user", method=RequestMethod.POST)
public createUser(Model model, #ModelAttribute("user") User user, BindingResult result){
UserValidator userValidator = new UserValidator();
userValidator.validate(user, result);
if (result.hasErrors()){
// do something
}
else {
// do something else
}
}
If there are validation errors, result.hasErrors() will be true.
Note : You can also set the validator in a #InitBinder method of the controller, with "binder.setValidator(...)" (in which case a mix use of method 1 and 2 would not be possible, because you replace the default validator). Or you could instantiate it in the default constructor of the controller. Or have a #Component/#Service UserValidator that you inject (#Autowired) in your controller : very useful, because most validators are singletons + unit test mocking becomes easier + your validator could call other Spring components.
Method 3 :
Why not using a combination of both methods? Validate the simple stuff, like the "name" attribute, with annotations (it is quick to do, concise and more readable). Keep the heavy validations for validators (when it would take hours to code custom complex validation annotations, or just when it is not possible to use annotations). I did this on a former project, it worked like a charm, quick & easy.
Warning : you must not mistake validation handling for exception handling. Read this post to know when to use them.
References :
A very interesting blog post about bean validation (Original link is dead)
Another good blog post about validation (Original link is dead)
Latest Spring documentation about validation
There are two ways to validate user input: annotations and by inheriting Spring's Validator class. For simple cases, the annotations are nice. If you need complex validations (like cross-field validation, eg. "verify email address" field), or if your model is validated in multiple places in your application with different rules, or if you don't have the ability to modify your model object by placing annotations on it, Spring's inheritance-based Validator is the way to go. I'll show examples of both.
The actual validation part is the same regardless of which type of validation you're using:
RequestMapping(value="fooPage", method = RequestMethod.POST)
public String processSubmit(#Valid #ModelAttribute("foo") Foo foo, BindingResult result, ModelMap m) {
if(result.hasErrors()) {
return "fooPage";
}
...
return "successPage";
}
If you are using annotations, your Foo class might look like:
public class Foo {
#NotNull
#Size(min = 1, max = 20)
private String name;
#NotNull
#Min(1)
#Max(110)
private Integer age;
// getters, setters
}
Annotations above are javax.validation.constraints annotations. You can also use Hibernate's
org.hibernate.validator.constraints, but it doesn't look like you are using Hibernate.
Alternatively, if you implement Spring's Validator, you would create a class as follows:
public class FooValidator implements Validator {
#Override
public boolean supports(Class<?> clazz) {
return Foo.class.equals(clazz);
}
#Override
public void validate(Object target, Errors errors) {
Foo foo = (Foo) target;
if(foo.getName() == null) {
errors.rejectValue("name", "name[emptyMessage]");
}
else if(foo.getName().length() < 1 || foo.getName().length() > 20){
errors.rejectValue("name", "name[invalidLength]");
}
if(foo.getAge() == null) {
errors.rejectValue("age", "age[emptyMessage]");
}
else if(foo.getAge() < 1 || foo.getAge() > 110){
errors.rejectValue("age", "age[invalidAge]");
}
}
}
If using the above validator, you also have to bind the validator to the Spring controller (not necessary if using annotations):
#InitBinder("foo")
protected void initBinder(WebDataBinder binder) {
binder.setValidator(new FooValidator());
}
Also see Spring docs.
Hope that helps.
I would like to extend nice answer of Jerome Dalbert. I found very easy to write your own annotation validators in JSR-303 way. You are not limited to have "one field" validation. You can create your own annotation on type level and have complex validation (see examples below). I prefer this way because I don't need mix different types of validation (Spring and JSR-303) like Jerome do. Also this validators are "Spring aware" so you can use #Inject/#Autowire out of box.
Example of custom object validation:
#Target({ TYPE, ANNOTATION_TYPE })
#Retention(RUNTIME)
#Constraint(validatedBy = { YourCustomObjectValidator.class })
public #interface YourCustomObjectValid {
String message() default "{YourCustomObjectValid.message}";
Class<?>[] groups() default {};
Class<? extends Payload>[] payload() default {};
}
public class YourCustomObjectValidator implements ConstraintValidator<YourCustomObjectValid, YourCustomObject> {
#Override
public void initialize(YourCustomObjectValid constraintAnnotation) { }
#Override
public boolean isValid(YourCustomObject value, ConstraintValidatorContext context) {
// Validate your complex logic
// Mark field with error
ConstraintViolationBuilder cvb = context.buildConstraintViolationWithTemplate(context.getDefaultConstraintMessageTemplate());
cvb.addNode(someField).addConstraintViolation();
return true;
}
}
#YourCustomObjectValid
public YourCustomObject {
}
Example of generic fields equality:
import static java.lang.annotation.ElementType.ANNOTATION_TYPE;
import static java.lang.annotation.ElementType.TYPE;
import static java.lang.annotation.RetentionPolicy.RUNTIME;
import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;
import javax.validation.Constraint;
import javax.validation.Payload;
#Target({ TYPE, ANNOTATION_TYPE })
#Retention(RUNTIME)
#Constraint(validatedBy = { FieldsEqualityValidator.class })
public #interface FieldsEquality {
String message() default "{FieldsEquality.message}";
Class<?>[] groups() default {};
Class<? extends Payload>[] payload() default {};
/**
* Name of the first field that will be compared.
*
* #return name
*/
String firstFieldName();
/**
* Name of the second field that will be compared.
*
* #return name
*/
String secondFieldName();
#Target({ TYPE, ANNOTATION_TYPE })
#Retention(RUNTIME)
public #interface List {
FieldsEquality[] value();
}
}
import java.lang.reflect.Field;
import javax.validation.ConstraintValidator;
import javax.validation.ConstraintValidatorContext;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.util.ReflectionUtils;
public class FieldsEqualityValidator implements ConstraintValidator<FieldsEquality, Object> {
private static final Logger log = LoggerFactory.getLogger(FieldsEqualityValidator.class);
private String firstFieldName;
private String secondFieldName;
#Override
public void initialize(FieldsEquality constraintAnnotation) {
firstFieldName = constraintAnnotation.firstFieldName();
secondFieldName = constraintAnnotation.secondFieldName();
}
#Override
public boolean isValid(Object value, ConstraintValidatorContext context) {
if (value == null)
return true;
try {
Class<?> clazz = value.getClass();
Field firstField = ReflectionUtils.findField(clazz, firstFieldName);
firstField.setAccessible(true);
Object first = firstField.get(value);
Field secondField = ReflectionUtils.findField(clazz, secondFieldName);
secondField.setAccessible(true);
Object second = secondField.get(value);
if (first != null && second != null && !first.equals(second)) {
ConstraintViolationBuilder cvb = context.buildConstraintViolationWithTemplate(context.getDefaultConstraintMessageTemplate());
cvb.addNode(firstFieldName).addConstraintViolation();
ConstraintViolationBuilder cvb = context.buildConstraintViolationWithTemplate(context.getDefaultConstraintMessageTemplate());
cvb.addNode(someField).addConstraintViolation(secondFieldName);
return false;
}
} catch (Exception e) {
log.error("Cannot validate fileds equality in '" + value + "'!", e);
return false;
}
return true;
}
}
#FieldsEquality(firstFieldName = "password", secondFieldName = "confirmPassword")
public class NewUserForm {
private String password;
private String confirmPassword;
}
If you have same error handling logic for different method handlers, then you would end up with lots of handlers with following code pattern:
if (validation.hasErrors()) {
// do error handling
}
else {
// do the actual business logic
}
Suppose you're creating RESTful services and want to return 400 Bad Request along with error messages for every validation error case. Then, the error handling part would be same for every single REST endpoint that requires validation. Repeating that very same logic in every single handler is not so DRYish!
One way to solve this problem is to drop the immediate BindingResult after each To-Be-Validated bean. Now, your handler would be like this:
#RequestMapping(...)
public Something doStuff(#Valid Somebean bean) {
// do the actual business logic
// Just the else part!
}
This way, if the bound bean was not valid, a MethodArgumentNotValidException will be thrown by Spring. You can define a ControllerAdvice that handles this exception with that same error handling logic:
#ControllerAdvice
public class ErrorHandlingControllerAdvice {
#ExceptionHandler(MethodArgumentNotValidException.class)
public SomeErrorBean handleValidationError(MethodArgumentNotValidException ex) {
// do error handling
// Just the if part!
}
}
You still can examine the underlying BindingResult using getBindingResult method of MethodArgumentNotValidException.
Find complete example of Spring Mvc Validation
import org.springframework.validation.Errors;
import org.springframework.validation.ValidationUtils;
import org.springframework.validation.Validator;
import com.technicalkeeda.bean.Login;
public class LoginValidator implements Validator {
public boolean supports(Class aClass) {
return Login.class.equals(aClass);
}
public void validate(Object obj, Errors errors) {
Login login = (Login) obj;
ValidationUtils.rejectIfEmptyOrWhitespace(errors, "userName",
"username.required", "Required field");
ValidationUtils.rejectIfEmptyOrWhitespace(errors, "userPassword",
"userpassword.required", "Required field");
}
}
public class LoginController extends SimpleFormController {
private LoginService loginService;
public LoginController() {
setCommandClass(Login.class);
setCommandName("login");
}
public void setLoginService(LoginService loginService) {
this.loginService = loginService;
}
#Override
protected ModelAndView onSubmit(Object command) throws Exception {
Login login = (Login) command;
loginService.add(login);
return new ModelAndView("loginsucess", "login", login);
}
}
Put this bean in your configuration class.
#Bean
public Validator localValidatorFactoryBean() {
return new LocalValidatorFactoryBean();
}
and then You can use
<T> BindingResult validate(T t) {
DataBinder binder = new DataBinder(t);
binder.setValidator(validator);
binder.validate();
return binder.getBindingResult();
}
for validating a bean manually. Then You will get all result in BindingResult and you can retrieve from there.
Validation groups
Also it is worth to mention validation for some more complex cases, when you have some "multi steps" within your business logic. In such cases we need "validation groups".
#Validated annotation was added to support "validation groups" in validated bean. This can be used in multi step forms where in the first step you need, for example, validate name and email, and in the second step you need to validate, for example, phone number.
With #Validated you first need to declare groups. Groups are declared with your custom marker interfaces.
#Validated example
Let's say we have a scenario when we have a form for user sign up. On this form we want user to provide a name and email. And after user is signed up we have another form where we suggest the user to add his some extra information, for example, email. We don't want email be provided on the first step. But it is required to provide it on the second step.
For this case, we'll declare two groups. First group would be OnCreate, and the second group would be OnUpdate :
OnCreate:
public interface OnCreate {}
OnUpdate:
public interface OnUpdate {}
Our user UserAccount class:
public class UserAccount {
// we will return this field after User is created
// and we want this field to be provided only on update
// so we can determine which user needs to be updated
#NotBlank(groups = OnUpdate.class)
private String id;
#NotBlank(groups = OnCreate.class)
private String name;
#NotBlank(groups = OnCreate.class)
private String email;
#NotBlank(groups = OnUpdate.class)
private String phone;
// standard constructors / setters / getters / toString
}
We mark the validation annotations with our groups interfaces depending on which group those validations are supposed to be related.
And finally our Controller methods:
#PostMapping(value = "/create")
public UserAccount createAccount(#Validated(OnCreate.class) #RequestBody UserAccount userAccount) {
...
}
#PatchMapping(value = "/update")
public UserAccount updateAccount(#Validated(OnUpdate.class) #RequestBody UserAccount userAccount) {
...
}
Here we specify #Validated(...) instead of #Valid and specify the validation group which should be used in different cases.
Now depending on validation group we'll perform the validations for the particular fields within different steps.
Related
I am trying to create a UniqueName annotation as a cutomize bean validation annotation for a create project api:
#PostMapping("/users/{userId}/projects")
public ResponseEntity createNewProject(#PathVariable("userId") String userId,
#RequestBody #Valid ProjectParam projectParam) {
User projectOwner = userRepository.ofId(userId).orElseThrow(ResourceNotFoundException::new);
Project project = new Project(
IdGenerator.nextId(),
userId,
projectParam.getName(),
projectParam.getDescription()
);
...
}
#Getter
#NoArgsConstructor(access = AccessLevel.PRIVATE)
class ProjectParam {
#NotBlank
#NameConstraint
private String name;
private String description;
}
#Constraint(validatedBy = UniqueProjectNameValidator.class)
#Retention(RetentionPolicy.RUNTIME)
#Target({ ElementType.FIELD })
public #interface UniqueName {
public String message() default "already existed";
public Class<?>[] groups() default {};
public Class<? extends Payload>[] payload() default{};
}
public class UniqueProjectNameValidator implements ConstraintValidator<UniqueName, String> {
#Autowired
private ProjectQueryMapper mapper;
public void initialize(UniqueName constraint) {
}
public boolean isValid(String value, ConstraintValidatorContext context) {
// how can I get the userId info??
return mapper.findByName(userId, value) == null;
}
}
The problem is that name field just need uniqueness for user level. So I need to get the {userId} from the URL field for validation. But how can I add this into the UniqueProjectNameValidator? Or is there some better way to handle this validation? This is just a small part of a large object, the real object has many other complex validations in the request handler which make the code quite dirty.
As #Abhijeet mentioned, dynamically passing the userId property to the constraint validator is impossible. As to how to handle this validation case better, there's the clean solution and the dirty solution.
The clean solution is to extract all the business logic to a service method, and validate the ProjectParam at the service level. This way, you can add a userId property to ProjectParam, and map it from the #PathVariable onto the #RequestBody before calling the service. You then adjust UniqueProjectNameValidator to validate ProjectParams rather than Strings.
The dirty solution is to use Hibernate Validator's cross-parameter constraints (see also this link for an example). You essentially treat both of your controller method parameters as the input for your custom validator.
If I'm not wrong, what you are asking is, how can you pass your userId to your custom annotation i.e. #UniqueName so that you can access the userId to validate projectName field against existing projectNames for passed userId.
It means you are asking about is, How to pass variable/parameter dynamically to annotation which is not possible. You have to use some other approach like Interceptors or Do the validation manually.
You can refer to the following answers as well:
How to pass value to custom annotation in java?
Passing dynamic parameters to an annotation?
#Mikhail Dyakonov in this article proposed a rule of thumb to choose the best validation method using java:
JPA validation has limited functionality, but it is a great choice for the simplest constraints on entity classes if such
constraints can be mapped to DDL.
Bean Validation is a flexible, concise, declarative, reusable, and readable way to cover most of the checks that you could have in
your domain model classes. This is the best choice, in most cases,
once you don't need to run validations inside a transaction.
Validation by Contract is a Bean validation for method calls. You can use it when you need to check input and output parameters of a
method, for example, in a REST call handler.
Entity listeners although they are not as declarative as the Bean validation annotations, they are a great place to check big
object's graphs or make a check that needs to be done inside a
database transaction. For example, when you need to read some data
from the DB to make a decision, Hibernate has analogs of such
listeners.
Transaction listeners are a dangerous yet ultimate weapon that works inside the transactional context. Use it when you need to decide
at runtime what objects have to be validated or when you need to check
different types of your entities against the same validation
algorithm.
I think Entity listeners match your unique constraint validation issue, because within the Entity Listener you'll be able to access your JPA Entity before persisting/updating it and executing your check query easier.
However as #crizzis pointed me, there is a significant restriction with this approach. As stated in JPA 2 specification (JSR 317):
In general, the lifecycle method of a portable application should not
invoke EntityManager or Query operations, access other entity
instances, or modify relationships within the same persistence
context. A lifecycle callback method may modify the non-relationship
state of the entity on which it is invoked.
Whether you try this approach, first you'll need an ApplicationContextAware implementation for getting current EntityManager instance. It's an old Spring Framework trick, maybe You're already using it.
import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Component;
#Component
public final class BeanUtil implements ApplicationContextAware {
private static ApplicationContext CONTEXT;
#Override
public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
CONTEXT = applicationContext;
}
public static <T> T getBean(Class<T> beanClass) {
return CONTEXT.getBean(beanClass);
}
}
This is my Entity Listener
#Slf4j
public class GatewaUniqueIpv4sListener {
#PrePersist
void onPrePersist(Gateway gateway) {
try {
EntityManager entityManager = BeanUtil.getBean(EntityManager.class);
Gateway entity = entityManager
.createQuery("SELECT g FROM Gateway g WHERE g.ipv4 = :ipv4", Gateway.class)
.setParameter("ipv4", gateway.getIpv4())
.getSingleResult();
// Already exists a Gateway with the same Ipv4 in the Database or the PersistenceContext
throw new IllegalArgumentException("Can't be to gateways with the same Ip address " + gateway.getIpv4());
} catch (NoResultException ex) {
log.debug(ex.getMessage(), ex);
}
}
}
Finally, I added this annotation to my Entity Class #EntityListeners(GatewaUniqueIpv4sListener.class)
You can find the complete working code here gateways-java
A clean and simple approach could be check validations in which you need to access the database within your transactional services. Even you could use the Specification, Strategy, and Chain of Responsibility patterns in order to implement a better solution.
I believe you can do what you're asking, but you might need to generalize your approach just a bit.
As others have mentioned, you can not pass two attributes into a validator, but, if you changed your validator to be class level validator instead of a field level validator, it can work.
Here is a validator we created that makes sure that two fields are the same value when submitted. Think of the password and confirm password use case that you often see websites, or email and confirm email use case.
Of course, in your particular case, you'll need to pass in the user's id and the name of the project that they are trying to create.
Annotation:
import javax.validation.Constraint;
import javax.validation.Payload;
import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;
import static java.lang.annotation.ElementType.ANNOTATION_TYPE;
import static java.lang.annotation.ElementType.TYPE;
import static java.lang.annotation.RetentionPolicy.RUNTIME;
/**
* Taken from:
* http://stackoverflow.com/questions/1972933/cross-field-validation-with-hibernate-validator-jsr-303
* <p/>
* Validation annotation to validate that 2 fields have the same value.
* An array of fields and their matching confirmation fields can be supplied.
* <p/>
* Example, compare 1 pair of fields:
*
* #FieldMatch(first = "password", second = "confirmPassword", message = "The password fields must match")
* <p/>
* Example, compare more than 1 pair of fields:
* #FieldMatch.List({
* #FieldMatch(first = "password", second = "confirmPassword", message = "The password fields must match"),
* #FieldMatch(first = "email", second = "confirmEmail", message = "The email fields must match")})
*/
#Target({TYPE, ANNOTATION_TYPE})
#Retention(RUNTIME)
#Constraint(validatedBy = FieldMatchValidator.class)
#Documented
public #interface FieldMatch {
String message() default "{constraints.fieldmatch}";
Class<?>[] groups() default {};
Class<? extends Payload>[] payload() default {};
/**
* #return The first field
*/
String first();
/**
* #return The second field
*/
String second();
/**
* Defines several <code>#FieldMatch</code> annotations on the same element
*
* #see FieldMatch
*/
#Target({TYPE, ANNOTATION_TYPE})
#Retention(RUNTIME)
#Documented
#interface List {
FieldMatch[] value();
}
}
The Validator:
import org.apache.commons.beanutils.BeanUtils;
import javax.validation.ConstraintValidator;
import javax.validation.ConstraintValidatorContext;
/**
* Taken from:
* http://stackoverflow.com/questions/1972933/cross-field-validation-with-hibernate-validator-jsr-303
*/
public class FieldMatchValidator implements ConstraintValidator<FieldMatch, Object> {
private String firstFieldName;
private String secondFieldName;
#Override
public void initialize(FieldMatch constraintAnnotation) {
firstFieldName = constraintAnnotation.first();
secondFieldName = constraintAnnotation.second();
}
#Override
public boolean isValid(Object value, ConstraintValidatorContext context) {
try {
Object firstObj = BeanUtils.getProperty(value, firstFieldName);
Object secondObj = BeanUtils.getProperty(value, secondFieldName);
return firstObj == null && secondObj == null || firstObj != null && firstObj.equals(secondObj);
} catch (Exception ignore) {
// ignore
}
return true;
}
}
Then here our command object:
import org.hibernate.validator.constraints.Length;
import org.hibernate.validator.constraints.NotBlank;
import javax.validation.GroupSequence;
#GroupSequence({Required.class, Type.class, Data.class, Persistence.class, ChangePasswordCommand.class})
#FieldMatch(groups = Data.class, first = "password", second = "confirmNewPassword", message = "The New Password and Confirm New Password fields must match.")
public class ChangePasswordCommand {
#NotBlank(groups = Required.class, message = "New Password is required.")
#Length(groups = Data.class, min = 6, message = "New Password must be at least 6 characters in length.")
private String password;
#NotBlank(groups = Required.class, message = "Confirm New Password is required.")
private String confirmNewPassword;
...
}
I just started using the #NotNull annotation with Java 8 and getting some unexpected results.
I have a method like this:
public List<Found> findStuff(#NotNull List<Searching> searchingList) {
... code here ...
}
I wrote a JUnit test passing in the null value for the argument searchingList. I was expecting some type of error to happen but it went through as though the annotation was not there. Is this expected behavior? From what I understood, this was to allow you to skip writing the boilerplate null check code.
An explanation of what exactly #NotNull is supposed to do would be greatly appreciated.
#Nullable and #NotNull do nothing on their own. They are supposed to act as Documentation tools.
The #Nullable Annotation reminds you about the necessity to introduce an NPE check when:
Calling methods that can return null.
Dereferencing variables (fields, local variables, parameters) that can be null.
The #NotNull Annotation is, actually, an explicit contract declaring the following:
A method should not return null.
A variable (like fields, local variables, and parameters) cannot should not hold null value.
For example, instead of writing:
/**
* #param aX should not be null
*/
public void setX(final Object aX ) {
// some code
}
You can use:
public void setX(#NotNull final Object aX ) {
// some code
}
Additionally, #NotNull is often checked by ConstraintValidators (eg. in spring and hibernate).
The #NotNull annotation doesn't do any validation on its own because the annotation definition does not provide any ConstraintValidator type reference.
For more info see:
Bean validation
NotNull.java
Constraint.java
ConstraintValidator.java
As mentioned above #NotNull does nothing on its own. A good way of using #NotNull would be using it with Objects.requireNonNull
public class Foo {
private final Bar bar;
public Foo(#NotNull Bar bar) {
this.bar = Objects.requireNonNull(bar, "bar must not be null");
}
}
To make #NonNull active you need Lombok:
https://projectlombok.org/features/NonNull
import lombok.NonNull;
Follow: Which #NotNull Java annotation should I use?
If you are using Spring, you can force validation by annotating the class with #Validated:
import org.springframework.validation.annotation.Validated;
More info available here:
Javax #NotNull annotation usage
You could also use #NonNull from projectlombok (lombok.NonNull)
SO #NotNull just is a tag...If you want to validate it, then you must use something like hibernate validator jsr 303
ValidatorFactory validatorFactory = Validation.buildDefaultValidatorFactory();
Validator validator = validatorFactory.getValidator();
Set<ConstraintViolation<List<Searching>> violations = validator.validate(searchingList);
I do this to create my own validation annotation and validator:
ValidCardType.java(annotation to put on methods/fields)
#Constraint(validatedBy = {CardTypeValidator.class})
#Documented
#Target( { ElementType.ANNOTATION_TYPE, ElementType.METHOD, ElementType.FIELD })
#Retention(RetentionPolicy.RUNTIME)
public #interface ValidCardType {
String message() default "Incorrect card type, should be among: \"MasterCard\" | \"Visa\"";
Class<?>[] groups() default {};
Class<? extends Payload>[] payload() default {};
}
And, the validator to trigger the check:
CardTypeValidator.java:
public class CardTypeValidator implements ConstraintValidator<ValidCardType, String> {
private static final String[] ALL_CARD_TYPES = {"MasterCard", "Visa"};
#Override
public void initialize(ValidCardType status) {
}
public boolean isValid(String value, ConstraintValidatorContext context) {
return (Arrays.asList(ALL_CARD_TYPES).contains(value));
}
}
You can do something very similar to check #NotNull.
To test your method validation in a test, you have to wrap it a proxy in the #Before method.
#Before
public void setUp() {
this.classAutowiredWithFindStuffMethod = MethodValidationProxyFactory.createProxy(this.classAutowiredWithFindStuffMethod);
}
With MethodValidationProxyFactory as :
import org.springframework.context.support.StaticApplicationContext;
import org.springframework.validation.beanvalidation.MethodValidationPostProcessor;
public class MethodValidationProxyFactory {
private static final StaticApplicationContext ctx = new StaticApplicationContext();
static {
MethodValidationPostProcessor processor = new MethodValidationPostProcessor();
processor.afterPropertiesSet(); // init advisor
ctx.getBeanFactory()
.addBeanPostProcessor(processor);
}
#SuppressWarnings("unchecked")
public static <T> T createProxy(T instance) {
return (T) ctx.getAutowireCapableBeanFactory()
.applyBeanPostProcessorsAfterInitialization(instance, instance.getClass()
.getName());
}
}
And then, add your test :
#Test
public void findingNullStuff() {
assertThatExceptionOfType(ConstraintViolationException.class).isThrownBy(() -> this.classAutowiredWithFindStuffMethod.findStuff(null));
}
I resolved it with
#JsonSetter(nulls = Nulls.AS_EMPTY)
#NotBlank
public String myString;
Request Json:
{
myString=null
}
Response:
error must not be blank
I have implemented a custom annotation #Password to perform validation on an argument of my method setPassword(). The annotation is defined like this:
// Password.java
import java.lang.annotation.*;
import static java.lang.annotation.ElementType.*;
import static java.lang.annotation.RetentionPolicy.*;
import javax.validation.*;
#Target({METHOD, FIELD, PARAMETER, ANNOTATION_TYPE})
#Retention(RUNTIME)
#Constraint(validatedBy = PasswordValidator.class)
#Documented
public #interface Password {
String message() default PasswordValidator.message;
Class<?>[] groups() default {};
Class<? extends Payload>[] payload() default {};
}
And the current implementation of the validator is this:
// PasswordValidator.java
package utils;
import javax.validation.ConstraintValidator;
import javax.validation.ConstraintValidatorContext;
public class PasswordValidator implements ConstraintValidator<Password, String> {
/* Default error message */
final static public String message = "error.invalid.password";
/**
* Validator init
* Can be used to initialize the validation based on parameters
* passed to the annotation.
*/
public void initialize(Password constraintAnnotation) {
System.out.println("in initialize()");
}
public boolean isValid(String string, ConstraintValidatorContext constraintValidatorContext) {
System.out.println("in isValid()");
return false;
}
}
Note that in the current implementation isValid() always returns false. The reason will be apparent shortly.
My usage of the validator is in a class User. For brevity I won't post the whole source here, but the relevant parts are:
package models;
import utils.Password;
// other imports omitted
#Entity
#Table(name = "users", schema="public")
public class User {
#Required
private String password;
...
public void setPassword(#Password String clearPassword) {
try {
this.password = HashHelper.createPassword(clearPassword);
} catch (AppException e) {
e.printStackTrace();
}
}
...
}
The basic idea is that I use the User class to store a hashed password for a user, but before setting the hashed password, I (would like to) run validation on the unhashed password (i.e. clearPassword).
The problem I am having is that this validation is not taking place. In the current implementation, it should (according to my understanding) always throw a ConstraintViolationException because isValid() always returns false, but this is not the case.
I have checked that the annotation is being attached to the method argument by calling (in another part of the application) something along the lines of:
Method method = user.getClass().getMethod("setPassword", new Class[] { String.class });
Annotation[][] parameterAnnotations = method.getParameterAnnotations();
System.out.println(method.getName() + ": " + parameterAnnotations[0][0]);
which produces the following output:
setPassword:#utils.Password(message=error.invalid.password, payload=[], groups=[])
So this tells me the annotation is being applied to the method argument. But I can't understand why I'm not getting the ConstraintViolationException when I actually call the method. I also never see the output "in initialize()" or "in isValid()" that I added to these methods as a check to see if they're being fired.
As another test, I also added the #Password annotation to the member variable password in User.class. This causes the ConstraintViolationException to be thrown as expected, e.g. when I try to persist a User object.
Can anyone shed light as to why the annotation on the method argument is not working properly? Thanks in advance!
I think you are missing this declaration in your Password annotation:
ConstraintTarget validationAppliesTo() default ConstraintTarget.IMPLICIT;
From the docs:
validationAppliesTo is used at constraint declaration time to clarify what the constraint targets (i.e. the annotated element, the method return value or the method parameters).
The element validationAppliesTo must only be present for constraints that are both generic and cross-parameter, it is mandatory in this situation. A ConstraintDefinitionException is raised if these rules are violated.
The type of the validationAppliesTo parameter is ConstraintTarget. The default value must be ConstraintTarget.IMPLICIT.
It won't get validated because hibernate validator validates on user object not on the method setPassword. In case you want to throw that exception, you have to get the ExecutableValidator instance, call validateParameters method and then throw the ConstraintViolationException by yourself.
I am writing code that has explicit call to Bean Validation (JSR-303) something like this:
public class Example {
#DecimalMin(value = "0")
private static final String ANNOTATED = "";
public void isPossitiveNumber(String str){
ValidatorFactory factory =
Validation.buildDefaultValidatorFactory();
ConstraintValidator<DecimalMin, String>
validator =
factory.getConstraintValidatorFactory().getInstance(
DecimalMinValidatorForString.class);
validator.initialize(
ReflectionUtils.findField(getClass(), "ANNOTATED")
.getAnnotation(
DecimalMin.class));
boolean isValid = validator.isValid(str, null);
return isValid;
}
}
Note the line boolean isValid = validator.isValid(str, null);
I transfer null for ConstraintValidatorContext because I found no way to obtain/construct it. In this particular case, this if fine, because there is no use of the ConstraintValidatorContext internally, but it is obvious a hack. How should I get ConstraintValidatorContext?
ADDED
I was asked to provide use-cases. So, for example, I am writting custom validator and I want to reuse exisiting validations. Or I am writting plane Java code as desribed above and I want to reuse exisiting validation.
I recently had exactly the same issue as the OP. However contrary to the accepted answer it is possible to write Unit tests that include the ConstraintValidationContext. This excellent link explains how to do it, http://farenda.com/java/bean-validation-unit-testing/
Basically you need to use the ValidatorFactory to obtain a Validator interface, then call validate(c) on that interface, where the parameter c is an instance of the class containing the bean validation annotations. A code example is clearer, code sample taken from the above link.
public class Player {
// name have to be 3 chars:
#Size(min = 3, max = 3)
private String name;
// possible score in game:
#Min(0) #Max(100)
private int score;
public Player(String name, int score) {
this.name = name;
this.score = score;
}
// just for logs
#Override
public String toString() {
return "Player{name='" + name + '\'' + ", score=" + score + '}';
}
}
public class PlayerValidationTest {
private static ValidatorFactory validatorFactory;
private static Validator validator;
#BeforeClass
public static void createValidator() {
validatorFactory = Validation.buildDefaultValidatorFactory();
validator = validatorFactory.getValidator();
}
#AfterClass
public static void close() {
validatorFactory.close();
}
#Test
public void shouldDetectInvalidName() {
//given too short name:
Player player = new Player("a", 44);
//when:
Set<ConstraintViolation<Player>> violations
= validator.validate(player);
//then:
assertEquals(violations.size(), 1);
}
}
The simple answer is you cannot. ConstraintValidatorContext is an interface and there is no Bean Validation API to get an instance like this. You could write your own implementation, but to implement it properly you would have to re-implement a lot of functionality of a Bean Validation provider. Look for example at the Hibernate Validator specific implementation - https://github.com/hibernate/hibernate-validator/blob/master/engine/src/main/java/org/hibernate/validator/internal/engine/constraintvalidation/ConstraintValidatorContextImpl.java
That said, I believe your attempt of reuse is misguided. This is not in the indent of Bean Validation and you are ending up with non portable and hard to maintain code. If you want to reuse existing constraints have a look at constraint composition, for example #NotEmpty reusing #NotNull and #Size
#Documented
#Constraint(validatedBy = { })
#Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
#Retention(RUNTIME)
#ReportAsSingleViolation
#NotNull
#Size(min = 1)
public #interface NotEmpty {
String message() default "{org.hibernate.validator.constraints.NotEmpty.message}";
Class<?>[] groups() default { };
Class<? extends Payload>[] payload() default { };
/**
* Defines several {#code #NotEmpty} annotations on the same element.
*/
#Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
#Retention(RUNTIME)
#Documented
public #interface List {
NotEmpty[] value();
}
}
You should declare a group for the constraints you validate in that case. Then you can call the normal validation for that group. See sections 2.1.1.2 and section 3.4 of the spec for group definitions and their semantics. For validating the group, you then just need to call Validator.validate(T Object, Class<?>... groups). There is no need to mess around with the ConstraintValidatorContext in this case.
I'm trying to create a simple custom validator for my project, and I can't seem to find a way of getting seam to validate things conditionally.
Here's what I've got:
A helper/backing bean (that is NOT an entity)
#RequiredIfSelected
public class AdSiteHelper {
private Date start;
private Date end;
private boolean selected;
/* getters and setters implied */
}
What I need is for "start" and "end" to be required if and only if selected is true.
I tried creating a custom validator at the TYPE target, but seam doesn't seem to want to pick it up and validate it. (Maybe because it's not an entity?)
here's the general idea of my custom annotation for starters:
#ValidatorClass(RequiredIfSelectedValidator.class)
#Target(ElementType.TYPE)
#Retention(RetentionPolicy.RUNTIME)
public #interface RequiredIfSelected {
String message();
}
public class RequiredIfSelectedValidator implements Validator<RequiredIfSelected>, Serializable {
public boolean isValid(Object value) {
AdSiteHelper ash = (AdSiteHelper) value;
return !ash.isSelected() || (ash.getStart() && ash.getEnd());
}
public void initialize(RequiredIfSelected parameters) { }
}
I had a similar problem covered by this post. If your Bean holding these values is always the same then you could just load the current instance of it into your Validator with
//Assuming you have the #Name annotation populated on your Bean and a Scope of CONVERSATION or higher
AdSiteHelper helper = (AdSiteHelper)Component.getInstance("adSiteHelper");
Also as you're using Seam your validators don't need to be so complex. You don't need an interface and it can be as simple as
#Name("requiredIfSelectedValidator")
#Validator
public class RequiredIfSelectedValidator implements javax.faces.validator.Validator {
public void validate(FacesContext context, UIComponent component, Object value) throws ValidatorException {
//do stuff
}
}