复选框值在错误时不会绑定到对象中？ [英] Checkbox values do not bind into object when false?

问题描述

我使用 ModelAttribute 在Spring Web应用程序中绑定对象。

一旦我注意到，布尔值A为true，如果我们取消选中A的复选框，则其值不会更新。

例如，我有一个Lesson对象，它具有属性活动=真。
在编辑课程视图中，我制作了一个复选框，将其绑定到活动。如果选中该复选框（绑定对象反映更改），事情就会正常运行，但如果我们取消选中复选框，对象课程将不会更改。

进一步的研究告诉我这是因为复选框的值可能不会被浏览器提交（这是HTML的设计）。因此，我必须使用丑陋的 request.getParameter 来检查是否设置了该值。

我刚刚通过这个问题 ，我发现asp.net mvc提供了一种更优雅的解决方法。我认为Spring必须提供类似的东西。有人知道如何做到这一点吗？

以下是我的代码：

控制器代码：

  @RequestMapping（value =/ test，method = RequestMethod.POST）
 public String processEditLesson（@Valid Lesson lesson，BindingResult bindingResult，Model model）{
 System.out.println（Lesson is active：+ lesson.isActive（））; //即使复选框未设置，仍然为true
 
 //当前解决方法
 String isActive = request.getParameter（active）; 
 if（StringUtils.isNotNullOrEmpty（isActive））{
 lesson.setActive（true）; 
} else {
 lesson.setActive（false）; 
} 
 ... 
} 
  

查看代码：

 < form id =lessonclass =EditorFormaction =$ {rc.getContextUrl（'/ test.html '）}method =post> 
 
< fieldset> 
< legend>< @ spring.message code =lesson.edit/>< / legend> 
 <@ spring.formHiddenInputlesson.id/> 
 <@ spring.formHiddenInputlesson.studio.id/> 
 
< div class =Entry> 
< label for =name>< @ spring.message code =lesson.message/>< / label> 
 <@ spring.formInputlesson.message/> 
< span class =ErrorMessage>< @spring.showErrors< br /> />< /跨度> 
< / div> 
 
< input type =checkboxname =activechecked =checked/> 
< label for =active> $ {rc.getMessage（'lesson.active'）}< / label> 
 
< input type =submitvalue =< @spring.message code ='common.update'/> /> 
< / fieldset> 
< / form> 
  

解决方案

Spring有一个内置的解决方法。

只需将这个额外的隐藏字段添加到表单中即可：

< input type =hidden value =onname =_ active/>

带有前导下划线的参数是某种标记，存在具有相同名称但没有下划线的复选框参数。

如果只有 _active = on ，Spring现在应该将 lesson.active 设置为false。 code>被提交。

I used ModelAttribute to bind object in Spring web application.

Once I notice that, in case an object has an boolean value A is true, its value will not be updated if we uncheck A's checkbox.

For example, I have a Lesson object which has the attribute "active" = true. In "Edit Lesson" view, I make a checkbox which bind into "active". Things work well if the checkbox is checked (the binding object reflect the changes), but the object lesson will not change if we un-check the checkbox.

Further study tells me that's because the checkbox value may not get submitted by browser (this is an in-design of HTML). So I have to use the ugly request.getParameter to check if the value is set.

I just come by this question, and I see that asp.net mvc provide a way to work around it more elegantly. I think Spring must provide something similarly. Does anyone know how to do that?

Following is my code:

Controller code:

    @RequestMapping(value="/test", method = RequestMethod.POST)
    public String processEditLesson(@Valid Lesson lesson, BindingResult bindingResult, Model model) {
        System.out.println("Lesson is active: " + lesson.isActive()); // still "true" even if the checkbox is unset

        // Current work-around
        String isActive = request.getParameter("active");
        if (StringUtils.isNotNullOrEmpty(isActive)) {
            lesson.setActive(true);
        } else {
            lesson.setActive(false);
        }
        ...
    }

View code:

<form id="lesson" class="EditorForm" action="${rc.getContextUrl('/test.html')}" method="post" >

    <fieldset>
        <legend><@spring.message code="lesson.edit"/></legend>
        <@spring.formHiddenInput "lesson.id" />
        <@spring.formHiddenInput "lesson.studio.id" />

        <div class="Entry">
            <label for="name"><@spring.message code="lesson.message"/></label>
            <@spring.formInput "lesson.message" />
            <span class="ErrorMessage"><@spring.showErrors "<br/>" /></span>
        </div>

        <input type="checkbox" name="active" checked="checked" />
        <label for="active">${rc.getMessage('lesson.active')}</label>

        <input type="submit" value="<@spring.message code='common.update' />" />
    </fieldset>
</form>

解决方案

Spring has a built in workaround.

Simply add this additional hidden field to the form:

<input type="hidden" value="on" name="_active"/>

The parameter with a leading underscore is some kind of marker, to indicate the existence of a checkbox parameter with the same name, but without the underscore.

Spring should now set lesson.active to false if only _active=on is submitted.

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