如何在Spring-MVC方法中绑定抽象类的子类? [英] How to bind a subclass of an abstract class in a Spring-MVC method?
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问题描述
在Spring-MVC控制器中给出保存"方法:
Given a "save" method in a Spring-MVC controller:
@RequestMapping(value = "/save")
public void save(@ModelAttribute(MY_KEY) final MyModel myModel) { ... }
在myModel
参数中具有作为抽象类的属性:
with a property in the myModel
parameter that is an abstract class:
public class MyModel {
public AbstractFruit fruit;
}
有什么方法可以指定请求中特定子类(例如Apple
)的使用?
Is there any way of specifying use of a particular subclass (e.g. Apple
) in the request?
推荐答案
您可以在控制器类中使用自定义的初始化绑定器方法:
You can use custom init binder method in your controller class:
// Additionally using MY_KEY as "value" parameter of this annotation
// is not working in some cases
@InitBinder
public void initBinder(WebDataBinder webDataBinder, HttpServletRequest servletRequest) {
// Probably you only want to init this when form is submitted
if (!"POST".equalsIgnoreCase(httpServletRequest.getMethod()) {
return;
}
// Filter out all request when we have nothing to do
Object nonCastedTarget = webDataBinder.getTarget();
if (nonCastedTarget == null || !(nonCastedTarget instanceof MyModel)) {
return;
}
MyModel target = (MyModel) nonCastedTarget;
if (/* some condition */) {
target.setFruit(new Apple());
} else {
target.setFruit(new Banana());
}
}
然后,Spring表单绑定机制将正确设置Apple/Banana类中的所有字段.
Spring form binding mechanism will then correctly set all fields in Apple/Banana class.
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