Java Bean Validation (JSR303) constraints involving relationship between several bean properties

Question

Say I have the following simple java bean:

class MyBean {    private Date startDate;    private Date endDate;    //setter, getters etc... } 

Is there a mechanism in JSR 303 to create a custom validator that validates the constraint that startDate must be before endDate?

It seems to me to be a common use case, yet I cannot find any examples of this kind of multiple property relationsship constraint.

Answer 1

I can think of a few things to try.

You could create a Constraint with a target of the type itself with an appropriate validator:

@ValidateDateRange(start="startDate", end="endDate") public class MyBean { 

You could encapsulate a date range in a type and validate that:

public class DateRange {       private long start;   private long end;    public void setStart(Date start) {     this.start = start.getTime();   }    // etc. 

You could add a simple property that performs the check:

public class MyBean {   private Date startDate;   private Date endDate;    @AssertTrue public boolean isValidRange() {     // TODO: null checks     return endDate.compareTo(startDate) >= 0;   } 

Answer 2

If you're using Hibernate Validator in version 4.1 or later you can use the @ScriptAssert constraint together with a scripting or expression language to express this kind of constraint. Using JavaScript your example would look like this:

 @ScriptAssert(lang = "javascript", script = "_this.startDate.before(_this.endDate)")  public class CalendarEvent {        private Date startDate;        private Date endDate;        //...  }  

You can get an even more compact syntax by creating a custom constraint for the script language of your choice:

@JexlAssert("_.startDate < _.endDate") public class CalendarEvent {      private Date startDate;      private Date endDate;      //... }