问题描述
有人可以告诉我，我需要在< form：select> 路径属性及其用途中指定什么？实际上我需要了解下拉列表中所选项目的值是如何传递给控制器的？
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?
推荐答案
说你有一个model（例如Dog）， Dog 有各种属性：
name
age
品种
Say you have a model (Dog for example), a Dog has various attributes:
name
age
breed
如果你想制作一个简单的表格来添加/编辑一只狗，你可以使用这样的东西：
if you want to make a simple form for adding/editing a dog, you'd use something that looks like this:
<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>
如你所见，我选择了品种属性为选择，因为我不希望用户输入他想要的任何品种，我想要他从列表中选择（在这种情况下 allBreeds ，控制器将传递给视图）。
As you can see, I've chosen the breed property to be a select, because I don't want the user to type whatever breed he want, I want him to choose from a list (allBreeds in this case, which the controller will pass to the view).
在< form：select> 我用路径告诉spring必须选择绑定到 Dog 模型的品种。
In the <form:select> I've used path to tell spring that the select has to bind to the breed of the Dog model.
我还使用< form：options> 来填充选项，其中包含品种属性的所有可用选项。
I've also used <form:options> to fill the select with all the options available for the breed attribute.
< form：select> 很聪明，如果它正在处理填充的模型（即 Dog 从数据库中获取或使用默认品种值 - 它会自动从列表中选择正确选项。
The <form:select> is smart, and if it's working on a populated model (i.e a Dog fetched from the database or with default breed value) - it will automatically select the "right" option from the list.
在这种情况下，控制器看起来很相似对此：
In this case, the controller will look similar to this:
@RequestMapping(value="/saveDog")
public String saveDog(@ModelAttribute("myDog") Dog dogFromForm){
//dogFromForm.getBreed() will give you the selected breed from the <form:select
...
//do stuff
...
}
我希望我的回答能给你一个大致的想法。
I hope my answer gave you a general idea.
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