如何在初始化绑定器中实例化具体类? [英] How instantiate a concrete class in init binder?

问题描述

我必须将抽象类绑定到我的控制器请求处理程序方法.

I have to bind an abstract class to my controller request handler method.

在我使用@ModelAttribute带注释的方法实例化具体类之前:

Before I instantiate the concrete class with @ModelAttribute annotated method:

@ModelAttribute("obj")
public AbstractObh getObj(final HttpServletRequest request){
    return AbstractObj.getInstance(myType);     
}

但是现在我尝试在没有@ModelAttribute注释方法的情况下执行此操作，因为每次调用控制器触发器模型属性注释方法也是如此.

But now I try to do that without the @ModelAttribute annotated method, beacause every call to controller trigger model attribute annotated method too.

因此，我尝试使用 InitBinder 和自定义编辑器来获得具体的类，但这是行不通的.

So I try to get concrete class with InitBinder and a custom editor, but it doesn't work.

我的Init活页夹:

@InitBinder(value="obj")
protected void initBinder(final WebDataBinder binder) {
    binder.registerCustomEditor(AbstractObj.class, new SchedaEditor());
}

和我的帖子处理程序:

@RequestMapping(method = RequestMethod.POST)
public String create(@Valid @ModelAttribute("obj") AbstractObj obj, final BindingResult bindingResult) {
    //my handler
    }

这是我的 ObjEditor :

@Override
public void setAsText(final String text) throws IllegalArgumentException {
    try{
        if(text == null){
            setValue(new ConcreteObj());
        }else{
            setValue(objService.findById(Long.valueOf(text)));
        }

    }catch(Exception e) {
        setValue(null);
    }
}

推荐答案

@ModelAttribute只是命令对象.它不打算具有依赖于请求参数的各种实现. WebDataBinder仅影响如何将所有参数映射到命令字段. 因此，请创建一个类型为AbstractObj的简单命令对象.

@ModelAttribute is just a command object. It is not intended to have variuos implementations depending on request parameters. WebDataBinder just influences how all parameters are being mapped to command fields. So - create simple command object with field of type AbstractObj .

public class CommandObject {

    private AbstractObj type;

    public void setType(AbstractObj type) {
        this.type = type;
    }

}

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