Difference between DataBinder and ConversionService in Spring

Question

I am experiencing some confusion in the use and purpose of Spring's DataBinder and ConversionService with regards to binding web requests to model objects. This has arisen because I have recently tried to use the JSR-303 validation by adding .

Prior to this I used:

<bean
    class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">
    <property name="webBindingInitializer">
        <bean class="mypackage.GlobalWebBindingInitializer" />
    </property>
</bean>

This was good because I wanted a global DataBinder that could be used by several Controllers. Within the GlobalWebBindingInitialzer class implement several of these:

binder.registerCustomEditor(MyClass.class, new PropertyEditorSupport(MyClass.class)

However I wanted to use the @Valid annotation and so added . The side-effect of this is that the above AnnotationMethodHandlerAdapter bean is already defined as part of the annotation-driven and so my global data binder is ignored.

So now I have created this class:

public class MyClassConverter implements Converter<String, MyClass>

I am confused. If I want to use should I use conversion service rather than databinder?

Answer 1

Historically Spring's data binding was used to convert data into javabeans. It relies heavily on JavaBean PropertyEditors to do the conversion.

Spring 3.0 added new and different support for conversions and formatting. Some of the changes included a "core.convert" package and a "format" package that as per the docs "may be used as simpler alternatives to PropertyEditors."

Now, to answer your question, yes, it looks like you're on the right track. You can continue to use either, but to make a long story short in many cases you should be able to use a converter instead of a data binder.

Documentation about how to add validation is available online.