Spring MVC Controller,如何在清空表单值时保持BindingResult错误

Question

我有一个使用Spring MVC Controller的Web表单.该表单由Spring验证.当存在验证错误时,Spring会显示相同的表单,预填充用户输入的值以及验证错误.

出于安全原因,我不希望表单预填充用户输入的值,但我确实需要显示验证错误.

我怎样才能做到这一点？

我通过查看Spring MVC源代码并了解如何构建BINDING_RESULT_KEY来实现此行为.这是源代码.

但是,这是一个hack,它可能会停止在新版本的Spring MVC上工作.

我该如何正确实现这一目标？

package com.nespresso.ecommerce.naw.controller;

import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.validation.BeanPropertyBindingResult;
import org.springframework.validation.BindingResult;
import org.springframework.validation.Errors;
import org.springframework.validation.ObjectError;
import org.springframework.validation.FieldError;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

import javax.validation.Valid;


@Controller
@RequestMapping("/my_form")
public class MyFormController extends FrontEndController {
    final String MY_FORM_OBJECT_NAME = "myForm";
    final String BINDING_RESULT_KEY = BindingResult.MODEL_KEY_PREFIX + "myForm";

    @RequestMapping(method = RequestMethod.POST)
    public String post(@Valid @ModelAttribute("myForm") MyForm myForm, Errors errors, Model model) {
        if (errors.hasErrors()) {
            emptyMyFormWhileKeepingFormErrors(model);
            return "my_form";
        }

        return "redirect:/confirmation";
    }

    @ModelAttribute("myForm")
    public MyForm myForm() {
        return new MyForm();
    }

    private void emptyMyFormWhileKeepingFormErrors(Model model) {
        BeanPropertyBindingResult bindingResult = (BeanPropertyBindingResult) model.asMap().get(BINDING_RESULT_KEY);
        if (bindingResult == null) {
            return;
        }
        MyForm emptyForm = myForm();

        // set the empty form, so the form is not pre-filled with the previous values.
        // However, this clears the validation errors also
        model.addAttribute(MY_FORM_OBJECT_NAME, emptyForm);

        // re-attach the validation errors, and empty the rejectedValue
        BeanPropertyBindingResult updatedBindingResult = new BeanPropertyBindingResult(emptyForm, MY_FORM_OBJECT_NAME);
        for (ObjectError oe : bindingResult.getAllErrors()) {
            if (!(oe instanceof FieldError)) {
                updatedBindingResult.addError(oe);
            } else {
                FieldError fieldError = (FieldError) oe;

                String rejectedValue = null;   // that's the point, create a copy of the FieldError, emptying the rejectedValue;

                FieldError updatedFieldError = new FieldError(
                        MY_FORM_OBJECT_NAME,
                        fieldError.getField(),
                        rejectedValue,
                        fieldError.isBindingFailure(),
                        fieldError.getCodes(),
                        fieldError.getArguments(),
                        fieldError.getDefaultMessage());
                updatedBindingResult.addError(updatedFieldError);
            }
        }

        model.addAttribute(BINDING_RESULT_KEY, updatedBindingResult);
    }
}

Answer 1

编辑:添加其他解决方案

只需将新值(从新初始化的对象)复制到模型属性中,您就可以拥有一个空模型对象,同时保留以前的错误org.springframework.beans.BeanUtils:

@RequestMapping(method = RequestMethod.POST)
public String post(@Valid @ModelAttribute("myForm") MyForm myForm, Errors errors, Model model) {
    if (errors.hasErrors()) {
        MyForm emptyForm = new MyForm();
        BeanUtils.copyProperties(emptyForm, myForm);
        return "my_form";
    }

    return "redirect:/confirmation";
}

这样,您仍然可以显示以前的错误,表单为空.

还有一个警告:如果我使用<input>字段时工作正常,而不是使用<form:input>弹簧增强字段使用被拒绝的值errors.

如果您希望继续使用<form:input>字段,则必须创建另一个BindingResult对象并使用当前错误对其进行初始化,只需将拒绝的值设置为null即可.您甚至可以重置所有字段或仅重置错误字段:

@RequestMapping(value = "/form", method=RequestMethod.POST)
public String update(@Valid @ModelAttribute Form form, BindingResult result, Model model) {
    if (result.hasErrors()) {
        // uncomment line below to reset all fields - by default only offending ones are
        //form = new Form();
        BeanPropertyBindingResult result2 = new BeanPropertyBindingResult(form, result.getObjectName());
        for(ObjectError error: result.getGlobalErrors()) {
            result2.addError(error);
        }
        for (FieldError error: result.getFieldErrors()) {
            result2.addError(new FieldError(error.getObjectName(), error.getField(), null, error.isBindingFailure(), error.getCodes(), error.getArguments(), error.getDefaultMessage()));
        }
        model.addAllAttributes(result2.getModel());
        return "my_form";
    }

    return "redirect:/confirmation";
}