将对象从下拉列表(.jsp)传递到控制器 [英] Pass object from Dropdown list (.jsp) to Controller

问题描述

我试图将一个对象(或只是ID)传递给我的控制器，该控制器是我从下拉列表中选择的.有2个类别: product 和 category ( product 包含一个外键，这是 category 的ID)这就是我将其加载到的方式:

I'm trying to pass an object (or just the ID) to my controller, which I select from a dropdown list. There are 2 classes: product and category (product contains a foreign key, which is the ID of category) This is how I load it into:

@RequestMapping(value="/edit", method=RequestMethod.GET)
public ModelAndView edit(@RequestParam(required=false) Long id) {
    ModelAndView mv = new ModelAndView();
    if (id == null) {
        mv.addObject(new Product());
    } else { 
        mv.addObject("product", productDao.findById(id));
    }
    mv.addObject("category", categoryDao.findAll());
    mv.setViewName("edit-product");
    return mv;
}

如您所见，我正在将对象 category 传递到我的.jsp文件中.我正在显示用户可以选择的所有类别.

As you can see, I'm passing the object category into my .jsp. There I'm displaying all the categories the user can select.

<select name="category">
<c:forEach items="${category}" var="category">
    <option name="category" value="${category.id}">${category.name}</option>
</c:forEach>
</select> 

该值应该传递给我的控制器，但我不知道如何传递它.

The value should be passed to my controller, but I don't know how to pass it.

@RequestMapping(value="/save", method=RequestMethod.POST)
public String save(Product product, Category category, Model model) {  
    product.setCategory(category); //not working, since the parameter isn't correct
    Product result = productDao.save(product);
    // set id from create
    if (product.getId() == null) {
        product.setId(result.getId());
}

推荐答案

将ID添加到您的选择中-该ID作为请求参数添加.

Add an Id to your select - the id is added as a request parameter.

<select name="category" id="categoryId">

和获取值的控制器

public String save(@RequestParam("categoryId") Long categoryId, Model model)

如果您的产品"产品具有"categoryId"字段(带有setter)，则可以仅使用产品"产品，而不能使用长" categoryId

If your Product product has categoryId field (with setter) you can use just Product product rather than Long categoryId

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