Use validators

Create a validator

• Create a class implement Validator interface
• Override supports and validate method
  • supports: check if a specific instance of a class can be validate from this validator'
  • validate: define the rules
• EX:

    @Override
    public boolean supports(Class<?> clazz) {
        return Account.class.equals(clazz);
    }

    @Override
    public void validate(Object target, Errors errors) {
        Account account = (Account) target;
        String regex = "^(?=.*[0-9])(?=.*[a-z])(?=.*[A-Z])(?=.*[@#$%^&+=])(?=\\S+$).{8,}$";
        Pattern p = Pattern.compile(regex);
        Matcher m = p.matcher(account.getPass());
        if(!m.matches()){
            errors.rejectValue("pass","account.pass", "The password must contain at least one lower case letter, one upper case letter, one digit and one of these special characters ~!@#$%^&*()_+");
        }
    }

• On that example the validation class support for Account class.
• The validate method validate for the password.

Indicate the controller use the validator

• Init a binder
• Add the validator to it
• When use @InitBinder the other validation will be Ignore (hibernate validation annotation, javax validation annotation....)

@InitBinder
public void initBinder(WebDataBinder binder) {
    binder.addValidators(new MyValidator());
}

• if you have more than 1 Validator class in binder the and when you use @Valid the binder will find in list to get the validation class that support for the model class.

Check valid a model attribute

• Import validation-api library
• Use @Valid annotation before @ModelAttribute parameter and add Errors as parameter

public String saveModel(@Valid @ModelAttribute MyModel myModel, Errors errors) {
    if (!erros.hasErrors()){
        // validated!
    } else {
        // not validated!
    }
}

Use Hibernate validators

• Import hibernate-validator library
• Use annotations as:
  • Field-level constraints

  @NotNull
  private String manufacturer;
  

  • Property-level constraints

  @NotNull
  public String getManufacturer() {
      return manufacturer;
  }
  

  • Class-level constraints

  @ValidPassengerCount
  public class Car { ... }
  

Hibernate Validator 5.x is the reference implementation Bean Validation 1.1

Annotations list

Annotation	Description
@AssertFalse	The annotated element must be a Boolean type and be false.
@AssertTrue	The annotated element must be a Boolean type and be true.
@DecimalMax	The annotated element must be a number whose value is less than or equal to a given BigDecimalString value.
@DecimalMin	The annotated element must be a number whose value is greater than or equal to a given BigDecimalString value.
@Digits	The annotated element must be a number whose value has a specified number of digits.
@Future	The value of the annotated element must be a date in the future.
@Max	The annotated element must be a number whose value is less than or equal to a given value.
@Min	The annotated element must be a number whose value is greater than or equal to a given value.
@NotNull	The value of the annotated element must not be null.
@Null	The value of the annotated element must be null.
@Past	The value of the annotated element must be a date in the past.
@Pattern	The value of the annotated element must match a given regular expression.
@Size	The value of the annotated element must be either a String, a collection, or an array whose length fits within the given range.

Note:

The Hibernate Validation Annotation not work:

If the hibernate validation annotation not work you must add the com.faster.xml:classmate and org.jboss.logging » jboss-logging libraries to your project because the hibernate validation is compiled dependencies on com.faster.xml:classmate, javax.validation » validation-api and org.jboss.logging » jboss-logging.

Making the validation object and validation annotation work together:

• Don't use @InitBindder
• Create the validation object and user validate() function.

@RequestMapping(value = "/register/", method = RequestMethod.POST)
public String register(@Valid @ModelAttribute("account") Account account, BindingResult result, HttpServletRequest request, SessionStatus status) {
        new AccountValidator().validate(account, result); //use with validate annotation
        if(result.hasErrors()){
            return "account/register";
        }

• The BindingResult result parameter must follow the @Valid | @Validated parameter

@RequestMapping(value = "/register/", method = RequestMethod.POST)
public String register(@Valid @ModelAttribute("account") Account account, BindingResult result,...)