I'd like to make Java Bean Validation constraints configurable by Spring, possibly by using properties. An example:
class Pizza {
@MaxGramsOfCheese(max = "${application.pizza.cheese.max-grams}")
int gramsOfCheese;
}
I haven't been able to get this to work or find much documentation about this.
Is something like this even possible? I know that messages are configurable in a Validationmessages.properties file, so I'm hoping something similar is possible for constraint values.
For any custom validation, you need to implement a custom validator by implementing the ConstraintValidator interface, and then provide that custom validator to the custom validation annotation that you create.
The custom validator:
public class MaxGramsOfCheeseValidator implements ConstraintValidator<MaxGramsOfCheese, Integer> {
@Value("${application.pizza.cheese.max-grams}")
protected int maxValue;
@Override
public void initialize(MaxGramsOfCheese constraintAnnotation) {
}
@Override
public boolean isValid(Integer value, ConstraintValidatorContext context) {
return value != null && value <= maxValue;
}
}
The custom validation annotation:
@Documented
@Constraint(validatedBy = {MaxGramsOfCheeseValidator.class})
@Target({ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
public @interface MaxGramsOfCheese {
String message() default "Some issue here"; //message to be returned on validation failure
Class<?>[] groups() default {};
Class<? extends Payload>[] payload() default {};
}
Using the custom validation annotation:
class Pizza {
@MaxGramsOfCheese
int gramsOfCheese;
}
Note that if you want the value for the annotation to be accessed from the properties file, you'll have to provide that in the custom validator as shown.
In addition to @Madhu Bhat you can configure your ConstraintValidator class to read properties from Spring's Environment.
public class MaxGramsOfCheeseValidator implements ConstraintValidator<MaxGramsOfCheese, Integer> {
@Autowired
private Environment env;
private int max;
public void initialize(MaxGramsOfCheese constraintAnnotation) {
this.max = Integer.valueOf(env.resolvePlaceholders(constraintAnnotation.max()));
}
@Override
public boolean isValid(Integer value, ConstraintValidatorContext context) {
return value != null && value <= this.max;
}
}
Thus you can use @MaxGramsOfCheese annotation on different fields with different parameters which may be more appropriate in your case.
class Pizza {
@MaxGramsOfCheese(max = "${application.pizza.cheddar.max-grams}")
int gramsOfCheddar;
@MaxGramsOfCheese(max = "${application.pizza.mozerella.max-grams}")
int gramsOfMozerella;
}
