Spring @ModelAttribute和翻译请求参数绑定名称

Question

I'm working on converting a legacy project to Spring (trying to adjust little as possible for now) and I'm running into a small issue with mapping/translating legacy parameters to a model attribute object. I may be completely wrong in thinking about this problem but it appears to me that to translate a parameter to a specific model attribute setter is to pass in the request parameter through a method for creating a model attribute and manually call the correct setter:

@ModelAttribute("form")
public MyForm createMyForm(@RequestParameter("legacy-param") legacy) {
    MyForm myForm = new MyForm();
    myForm.setNewParam(legacy);
    return myForm;
}

I don't necessarily want to change the request parameter name yet since some javascript and JSPs are depending on it being named that way but is there any way to do something like this? Or is there a different way to map/translate request parameters to model attributes?

public class MyForm {
    @ParameterName("legacy-param")
    private String newParam;

    public void setNewParam(String value) { ... }

    public String getNewParam() { ... }
}

@Controller
public class MyController {

    @RequestMapping("/a/url")
    public String myMethod(@ModelAttribute("form") MyForm myForm, BindingResult result) { ... }
}

Answer 1

The way you've written that model attribute method is indeed odd. I'm not entirely clear what you're actually trying to do.Assuming there are many parameters, you're going to end up with an awful lot of instances of MyForm in your ModelMap. A more 'normal' way to create model attribute would be like this:

@ModelAttribute("legacyParamNotCamel")
public MyForm createMyForm(@RequestParameter("legacy-param-not-camel") String legacy) {
    return legacy;
}

Then in the JSP you can refer to it directly in expression language. eg,

<c:out value="${legacyParamNotCamel}"/>

If you want to put them onto a form backing object, you need to do it all in a single method that creates the object, not make new copies of it in each method. (assuming your form has more than a single parameter associated with it.)

-- It seems like what you're really trying to do though is translate the parameter names in the request before the web data binder gets ahold of it, so that you can bind oddly named parameters onto a java bean? For that you'll need to use an interceptor that translates the names before the binding process begins, or make your own subclass of the databinder than can take a property name translation map.

Answer 2

You placed the @ModelAttribute at the Method Level but the intention seems to be more of a formBackingObject hence we should be dealing at the Method Parameter Level

There's a difference.

I put up an explanation here on my blog along examples at Spring 3 MVC: Using @ModelAttribute in Your JSPs at http://krams915.blogspot.com/2010/12/spring-3-mvc-using-modelattribute-in.html