Custom validation with Bean Validation (JSR-303)

In my previous post on Bean Validation I explained how to use built-in constrains. When the standard constraints aren’t enough, you can develop your own.

Custom constraint

Let’s create a custom constraint and have it checked that the first character is an uppercase one.

package me.m1key.jsf.constraints;

import static java.lang.annotation.ElementType.ANNOTATION_TYPE;
import static java.lang.annotation.ElementType.CONSTRUCTOR;
import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.ElementType.PARAMETER;

import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

import javax.validation.Constraint;
import javax.validation.Payload;

@Constraint(validatedBy = FirstUpperValidator.class)
public @interface FirstUpper {
 String message() default "{me.m1key.jsf.constraints.FirstUpper.message}";

 Class<?>[] groups() default {};

 Class<? extends Payload>[] payload() default {};

  • message - the error message. You can omit curly braces and just hard code it
  • groups - this is for grouping validations (if one group fails - other groups are not checked; here we use the default group)
  • payload - additional type-safe information might be carried here

Now, we need the validator.

Custom validator

package me.m1key.jsf.constraints;

import javax.validation.ConstraintValidator;
import javax.validation.ConstraintValidatorContext;

public class FirstUpperValidator implements
     ConstraintValidator<FirstUpper, String> {

 public void initialize(FirstUpper firstUpper) {
     // See JSR 303 Section 2.4.1 for sample implementation.

 public boolean isValid(String value, ConstraintValidatorContext context) {
     if (value == null || value.length() == 0) {
         return true;
     return value.substring(0, 1)
             .equals(value.substring(0, 1).toUpperCase());

Nothing special here. Finally, the usage...

The usage

It’s identical as any other constraint.
  @Size(min = 3)
  public String getName() {
      return name;


I showed you how to write custom constraints and gave a hint about existence and purpose of groups and payloads.

Download source code for this article

Read on


  1. Replies
    1. Great Article android based projects

      Java Training in Chennai

      Project Center in Chennai

      Java Training in Chennai

      projects for cse

      The Angular Training covers a wide range of topics including Components, Angular Directives, Angular Services, Pipes, security fundamentals, Routing, and Angular programmability. The new Angular TRaining will lay the foundation you need to specialise in Single Page Application developer. Angular Training

  2. Thank you, nice job!! It helps me a lot!!!

  3. Hi, Great.. Tutorial is just awesome..It is really helpful for a newbie like me.. I am a regular follower of your blog. Really very informative post you shared here. Kindly keep blogging. If anyone wants to become a Java developer learn from Java Training in Chennai. or learn thru Java Online Training in India . Nowadays Java has tons of job opportunities on various vertical industry.