Java spring 标签中的 <form:select path> 是做什么用的？
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What is <form:select path> in spring tag used for?
提问by Shivayan Mukherjee
Can someone please tell me what do I need to specify in <form:select>path attribute and what it's used for? actually I need to understand how the value of the selected item from the dropdown is passed onto the controller?
有人可以告诉我我需要在<form:select>path 属性中指定什么以及它的用途吗？实际上我需要了解如何将下拉列表中所选项目的值传递给控制器？
回答by Shay Elkayam
Say you have a model (Dog for example), a Doghas various attributes:
name
age
breed
假设您有一个模型（例如 Dog），aDog具有多种属性：
name
age
品种
if you want to make a simple form for adding/editing a dog, you'd use something that looks like this:
如果您想制作一个用于添加/编辑狗的简单表单，您可以使用如下所示的内容：
<form:form action="/saveDog" modelAttribute="myDog">
<form:input path="name"></form:input>
<form:input path="age"></form:input>
<form:select path="breed">
<form:options items="${allBreeds}" itemValue="breedId" itemLabel="breedName" />
</form:select>
</form:form>
As you can see, I've chosen the breedproperty to be a select, because I don't want the user to typewhatever breed he want, I want him to choose from a list(allBreedsin this case, which the controller will pass to the view).
如您所见，我选择了breed属性为 a select，因为我不希望用户输入他想要的任何品种，我希望他从列表中进行选择（allBreeds在这种情况下，控制器将传递给看法）。
In the <form:select>I've used pathto tell spring that the select has to bind to the breedof the Dogmodel.
在<form:select>我用path告诉弹簧选择具有绑定到breed了的Dog模型。
I've also used <form:options>to fill the select with all the options available for the breedattribute.
我还习惯使用<form:options>可用于该breed属性的所有选项来填充选择。
The <form:select>is smart, and if it's working on a populated model (i.e a Dogfetched from the database or with default breed value) - it will automatically select the "right" option from the list.
这<form:select>是智能的，如果它正在处理填充模型（即Dog从数据库中获取或具有默认品种值） - 它会自动从列表中选择“正确”选项。
In this case, the controller will look similar to this:
在这种情况下，控制器看起来类似于：
@RequestMapping(value="/saveDog")
public String saveDog(@ModelAttribute("myDog") Dog dogFromForm){
//dogFromForm.getBreed() will give you the selected breed from the <form:select
...
//do stuff
...
}
I hope my answer gave you a general idea.
我希望我的回答能让你有一个大致的了解。
