Validation on enum in spring request

Question

I have a request WorkerRequest in which there is an enum which has FULL_TIME , MANAGER and so on.

In WorkerRequest how can I apply the length validation on this enum?

Example: enum type should not be greater than 8 characters.

FULL_TIME valid (8 characters)

PERMANENT invalid (9 characters)

Currently if I put javax.validation.constraints.Size

  @Size(min = 0, max = 8, message = "Allowed length for workerType is 8.")
  @Enumerated(EnumType.STRING)
  private WorkerType workerType;

it throws an error :

HV000030: No validator could be found for constraint 'javax.validation.constraints.Size' validating type 'com.XX.XX.XX.WorkerType'. Check configuration for 'workerType'

Answer 1

As described in Difference between @Size, @Length and @Column(length=value)

@Size is a Bean Validation annotation that validates that the associated String has a value whose length is bounded by the minimum and maximum values.

You can only specify the the maximum required length for persisting enum value in your db. For example, if you define @Column(length = 8) instead of @Size you will see workerType VARCHAR(8) in your db definition correspondingly.

But there is a workaround for it: suppose you have

 public enum WorkerType {PERMANENT , FULL_TIME, ...}; 

1. Define a custom validation annotation:

    @Target(ElementType.FIELD) @Retention(RetentionPolicy.RUNTIME) @Constraint(validatedBy = EnumSizeLimit.class) public @interface EnumSizeLimit { String message() default "{com.example.app.EnumSizeLimit.message}"; Class<?>[] groups() default {}; Class<? extends Payload>[] payload() default {}; Class<? extends Enum<?>> targetClassType(); }

2. Implement a Validator:

    public class EnumSizeLimitValidator implements ConstraintValidator < EnumSizeLimit , String > { private Set < String > allowedValues; @SuppressWarnings({ "unchecked", "rawtypes" }) @Override public void initialize(EnumSizeLimit targetEnum) { Class << ? extends Enum > enumSelected = targetEnum.targetClassType(); allowedValues = (Set < String > ) EnumSet.allOf(enumSelected).stream().map(e - > ((Enum << ? extends Enum << ? >> ) e).name()) .collect(Collectors.toSet()); } @Override public boolean isValid(String value, ConstraintValidatorContext context) { return value == null || (value.length>=0 && value.length<=8)) ? true : false; } }

3. Define Field:

    @EnumSizeLimit (targetClassType = WorkerType.class, message = "your message" private String workerType;

Answer 2

I dont see the need of size validation. The fact of using enum in the request will oblige the serialization to map the value to one of the enum possible values. In case you fill the string json with "invalid" as worker type, spring will throw:

org.springframework.http.converter.HttpMessageNotReadableException: JSON parse error: Cannot deserialize value of type WorkerType from String "invalid": value not one of declared Enum instance names: etc.

You can catch the exception in a custom rest exception handler