I am using Spring Data JPA to model and validate my data. In this case I got a class that got both a password and confirm field:

public class RegistrationForm {

    private String password;

    private String confirm;

    // ...
}

and now I want to check if they both match. I figured out I can create a method for it using @AssertTrue:

@AssertTrue(message = "Passwords don't match")
private boolean isPasswordMatch() {
    return password.equals(confirm);
}

Now in my controller I validate this class and this method runs just fine. My problem now is that I couldn’t figure out how to display this error in my Thymeleaf template. I usually used this for fields with validation:

<span th:if="${#fields.hasErrors('username')}" th:errors="*{username}"></span>

But that doesn’t work with methods. Now I investigated a bit and found out that if I name the method something like isXXX then it is going to put a field into the Errors instance named XXX. In this case, it would be a field called passwordMatch. I could verify this using a debugger.

It doesn’t work, even though that field error exists as a ViolationFieldError like any other error. For reference I tried this:

<span th:if="${#fields.hasErrors('passwordMatch')}" th:errors="*{passwordMatch}"></span>

I simply get an error saying that the property is not readable:

Caused by: org.springframework.beans.NotReadablePropertyException: Invalid property 'passwordMatch' of bean class [me.squidxtv.tacocloud.model.RegistrationForm]: 
Bean property 'passwordMatch' is not readable or has an invalid getter method: Does the return type of the getter match the parameter type of the setter?

Note: I am currently going through “Spring in Action” 6th edition and this comes up in chapter 5 “Securing Spring” but my question isn’t related to it, because the book itself doesn’t implement validation for that class.