The Spring form macros contains macros to display global or field specific error messages:

<form action="handlerUri" method="post">
  <label for="email">Email:</label>
    <@spring.bind path="nameOfForm.email"/>
    <@spring.formInput path="nameOfForm.email"/>
    <@spring.showErrors "<br>", "notification error"/>

  <label for="emailRepeat">Repeat Email:</label>
    <@spring.bind path="nameOfForm.emailRepeat"/>
    <@spring.formInput path="nameOfForm.emailRepeat"/>
    <@spring.showErrors "<br>", "notification error"/>

  <input type="submit" value="Subscribe"/>
</form>

See showErrors macro documentation.