Java jsr 303从带注释的字段访问bean字段

Question

In my scenario I'm trying to create annotation that validates if one field is filled if another one has some kind of value.

The interface looks like this:

@Target({ElementType.FIELD, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Constraint(validatedBy = RequiredIfFieldHasValueValidator.class)
public @interface RequiredIfFieldHasValue
{
    String message() default "Required if selected";

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

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

    /*
    FieldName against which we validate
     */
    String fieldName() default "";

    /*
    Field value that indicates requirement
     */
    String fieldValue() default "";
} 

And implementation:

public class RequiredIfFieldHasValueValidator implements ConstraintValidator<RequiredIfFieldHasValue, String>
{
    private String fieldName;
    private String fieldValue;

    @Override
    public void initialize( RequiredIfFieldHasValue constraintAnnotation )
    {
        fieldName = constraintAnnotation.fieldName();
        fieldValue = constraintAnnotation.fieldValue();
        validateParameters();
    }

    @Override
    public boolean isValid( String value, ConstraintValidatorContext context )
    {
        System.out.println( "Validate against fieldname: " + fieldName + " fieldvalue: " + fieldValue );
        //
        //Validation should be here (1)
        //
        return false;
    }

    private void validateParameters()
    {
        if ( "".equals( fieldName ) || fieldName == null )
        {
            throw new IllegalArgumentException( "The fieldname cannot be null" );
        }
    }
}

And example usage:

public class Form {
    private String type;
    @RequiredIfFieldHasValue(fieldName = "type", fieldValue = "DICT")
    private String dictValue;
}

I use it in Spring MVC and validate on request like this:

public String myFormPostPost( Model model, @Valid @ModelAttribute MyForm form, indingResult result )

So my goal is: If field type has value equal to DICT, field dictValue should be required (not empty) .

My question is if I can access current bean values in Validation should be here (1) ? I know I could do annotation to whole bean, but I'd prefere it that way.

Answer 1

好吧，我想这是不可能的，所以我坚持使用带类注释的解决方案： 使用Hibernate Validator（JSR 303）进行跨字段验证