Spring 3.x way to trim all text fields

[Madkinder]

My goal is to trim leading and trailing whitespaces from all the input and textarea fields during form binding. I also need to be able to tweak this behavior (i.e. disable trimming for some particular field).

I've googled a lot and searched this forum and the only solution I ended up with is registering StringTrimmerEditor property editor in FormController.

But I'm worried about these concerns:

1. FormController class hierarchy is deprecated since Spring 3.0 in favor of annotated controllers
2. Spring 3.0 introduced type conversion which aims to substitute property editors

I guess this could be dealt with ApplicationConversionService (that ROO installs as of version 1.1.1) by I'm not sure.

So the questions are as follows:

• Can I achieve my goal w/o using PropertyEditors?
• Has FormattingConversionServiceFactory something to do with my problem?
• Is there any trimming formatter provided with Spring-MVC out of the box to replace StringTrimmerEditor?

[Osvaldas Grigas]

These are all valid questions, and I spent quite some time recently looking for easy solution to this "string trimming" issue, with no promising results.

I believe there's no elegant way of doing it, at least not in Spring 3.0. The best I could find involves the following steps:

1. Drop <mvc:annotation-driven/> namespace configuration.
2. Manually setup all the required Spring MVC infrastructure beans: FormattingConversionServiceFactoryBean, LocalValidatorFactoryBean, DefaultAnnotationHandlerMapping, AnnotationMethodHandlerAdapter, various types of HttpMessageConverter beans, etc.
3. Among all these infrastructure beans there will be a ConfigurableWebBindingInitializer. It has a property called "propertyEditorRegistrar" - pass it an instance of custom implementation of PropertyEditorRegistrar interface that registers StringTrimmerEditor:

public class StringTrimmerEditorRegistrar implements PropertyEditorRegistrar {

    public void registerCustomEditors(PropertyEditorRegistry registry) {
        registry.registerCustomEditor(String.class, new StringTrimmerEditor(" \t\r\n\f", true));
    }
}

All this setup seems like a lot of work for something as trivial as string trimming, and it is ugly as hell. So if you're reading this post and you know a better solution, you're more than welcome to share.

[Madkinder]

Thanks for your reply, Osvaldas.

Dropping <mvc:annotation-driven/> seems to be quite a load of work Moreover eventually I will end up with a property editor anyway, though as you know I'm trying to not to use property editors and move towards conversion service infrastructure. Thus this approach won't save me... unfortunately.

I guess I would need to debug through the whole process of binding and conversion to understand how it is done and how to wedge into this process properly. I will post here as soon as I have any progress.

[Osvaldas Grigas]

I just discovered an arguably cleaner solution to this. You can make all your controllers inherit from abstract superclass that initializes the DataBinder:

public abstract class BaseController {

    @InitBinder
    public void initBinder(WebDataBinder binder) {
        binder.registerCustomEditor(String.class, new StringTrimmerEditor(" \t\r\n\f", true));
    }
}

[Madkinder]

This solution still uses PropertyEditor while I want to use Conversion Service instead.