Using StringTrimmerEditor with Thymeleaf

Posted at — Jan 25, 2021

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Trimming whitespace is one of the little things that a developer should take care of when coding text inputs in an HTML form. Remembering to do this for each input will get tedious soon, and there is a big chance that you might forget about it sooner or later. Luckily, Spring has the StringTrimmerEditor class that allows to globally configure the trimming once.

To use this in a Spring Boot with Thymeleaf application, we can define an @ControllerAdvice annotated class like this:

import org.springframework.beans.propertyeditors.StringTrimmerEditor;
import org.springframework.web.bind.WebDataBinder;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.InitBinder;

@ControllerAdvice
public class GlobalControllerAdvice {

    @InitBinder (1)
    public void initBinder(WebDataBinder binder) {
        StringTrimmerEditor stringtrimmer = new StringTrimmerEditor(false); (2)
        binder.registerCustomEditor(String.class, stringtrimmer); (3)
    }
}

1	Methods annotated with `@InitBinder` will be called by the Spring framework to initialize the `WebDataBinder`.
2	Create a `StringTrimmerEditor` instance. The boolean flag indicates if you want to have an empty string returned as `null` (use `true`), or if an empty string should remain an empty string (use `false`).
3	Register the `StringTimmerEditor` to the binder for all fields of type `String`.

Now all excess whitespace will be trimmed automatically when the values are taken from the <input> fields and put in the form data object.

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Wim Deblauwe

Wim Deblauwe

Using StringTrimmerEditor with Thymeleaf