@InitBinder

Customizing WebDataBinder initialization 
To customize request parameter binding with PropertyEditors, etc. via Spring's WebDataBinder, you can either use @InitBinder-annotated methods within your controller or externalize your configuration by providing a custom WebBindingInitializer. 

Customizing data binding with @InitBinder 
Annotating controller methods with @InitBinder allows you to configure web data binding directly within your controller class. @InitBinder identifies methods which initialize the WebDataBinder which will be used for populating command and form object arguments of annotated handler methods. 
Such init-binder methods support all arguments that @RequestMapping supports, except for command/form objects and corresponding validation result objects. Init-binder methods must not have a return value. Thus, they are usually declared as void. Typical arguments include WebDataBinder in combination with WebRequest or java.util.Locale, allowing code to register context-specific editors. 
The following example demonstrates the use of @InitBinder for configuring a CustomDateEditor for all java.util.Date form properties. 

Java代碼   

1. @Controller  
2. public class MyFormController {  
3.   
4.     @InitBinder  
5.     public void initBinder(WebDataBinder binder) {  
6.         SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");  
7.         dateFormat.setLenient(false);  
8.         binder.registerCustomEditor(Date.class, new CustomDateEditor(dateFormat, false));  
9.     }  
10.   
11.     // ...  
12. }  

WebDataBinder是用來綁定請求參數到指定的屬性編輯器，可以繼承WebBindingInitializer來實現一個全部controller共享的dataBiner 

Java代碼   

1. @Component  
2. public class CommonBindingInitializer implements WebBindingInitializer {  
3.   
4.     public void initBinder(WebDataBinder binder, WebRequest request) {  
5.         SimpleDateFormat dateFormat = new SimpleDateFormat(ERPUtil.ISO_DATE_MASK);  
6.         dateFormat.setLenient(false);  
7.         binder.registerCustomEditor(Date.class, new CustomDateEditor(dateFormat, true));  
8.         binder.registerCustomEditor(String.class, new StringTrimmerEditor(false));  
9.     }  
10. }  

也可以在某個單獨的contorller里定義一個dataBinder，使用@InitBinder注解就可以實現 

PS：WebDataBinder是用來綁定請求參數到指定的屬性編輯器.由於前台傳到controller里的值是String類型的，當往Model里Set這個值的時候，如果set的這個屬性是個對象，Spring就會去找到對應的EDITOR進行轉換，然后再SET進去