With WebDataBinder, the empty value of Boolean is not Null but FALSE [SPR-17513]

[spring-issuemaster]

yoshikawaa opened SPR-17513 and commented

With WebDataBinder, why the empty value of Boolean is not Null but FALSE ?

Form backing bean

public class SampleForm {
  private Boolean finished;
  // getter and setter...
}

Request Parameter

• finished=true -> TRUE
• finished=false -> FALSE
• finished= -> Null
• _finished= -> FALSE ???

 

"_" prefixed value is converted to empty value in WebDataBinder#getEmptyValue .

 

If we use 3 pattern value (TRUE, FALSE, Null(=default)), it may becomes a problem.

Because the result are different when explicitly sending finished= and when implicit _finished= is sent.

 

Thanks.

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Affects: 4.3.20, 5.1.2

Reference URL: https://github.com/spring-projects/spring-framework/blob/v5.1.2.RELEASE/spring-web/src/main/java/org/springframework/web/bind/WebDataBinder.java#L282-L285

[spring-issuemaster]

Juergen Hoeller commented

A "_finished" field marker is explicitly meant to indicate that there was a checkbox that wasn't checked, effectively indicating false since an HTML form does not include a value parameter in such a case. No such field marker means that there actually was no such field, leading to null.

So if you'd like null for no value, then make sure that no field marker is sent along in the request.

[spring-issuemaster]

yoshikawaa commented

Thanks for your reply.

I understood this behavior is completely intentional by Spring MVC.

Depending on the requirements of the application, I will use Boolean property and marker parameter appropriately.