使用JSTL设置HTML下拉选择选项 [英] Set HTML dropdown selected option using JSTL

问题描述

在同样的上下文中，我有另一个查询

 < select multiple =multiplename =prodSKUs> 
< c：forEach items =$ {productSubCategoryList}var =productSubCategoryList> 
< option value =$ {productSubCategoryList}$ {productSubCategoryList == productSubCategoryName？ 'selected'：''}> $ {productSubCategoryList}< / option> 
< / c：forEach> 
< / select> 
  

以及请求中的相应设置就像

  for（int i = 0; i< userProductData.size（）; i ++）{
 String productSubCategoryName = userProductData.get（i）.getProductSubCategory（）; 
 System.out.println（productSubCategoryName）; 
 request.setAttribute（productSubCategoryName，productSubCategoryName）; 
 
 
 
 
 $ b $ p 
 $ b 
这里我有多个选择下拉菜单，即使我得到来自for的返回值为两个，在UI中只有一个数据会变得更亮，而不是第二个，代码中出现了什么错误？ 
 
解决方案
假设您有一个要放入组合的元素的集合$ {roles}，并且选择了元素$ {selected}，它将如下所示： 
 
 
 < select name ='role'> 
 < c：forEach items =$ {roles}var =role> 
  < / c：if> 
< / c：forEach> 
< / select> 
  
更新（下一个问题） 
 
 
您覆盖属性productSubCategoryName。在for循环的最后，最后一个productSubCategoryName。
 
 
由于表达式语言的局限性，我认为处理这个问题的最好方法是使用map ： 
 
 
 地图< String，Boolean> map = new HashMap< String，Boolean>（）; 
 for（int i = 0; i< userProductData.size（）; i ++）{
 String productSubCategoryName = userProductData.get（i）.getProductSubCategory（）; 
 System.out.println（productSubCategoryName）; 
 map.put（productSubCategoryName，true）; 
} 
 request.setAttribute（productSubCategoryMap，map）; 
  
然后在JSP中：
 < select multiple =multiplename =prodSKUs> 
< c：forEach items =$ {productSubCategoryList}var =productSubCategoryList> 
< option value =$ {productSubCategoryList}$ {not empty productSubCategoryMap [productSubCategoryList]？ 'selected'：''}> $ {productSubCategoryList}< / option> 
< / c：forEach> 
< / select> 
  
 
In the same context i have another query 
<select multiple="multiple" name="prodSKUs">
            <c:forEach items="${productSubCategoryList}" var="productSubCategoryList">
          <option value="${productSubCategoryList}"${productSubCategoryList == productSubCategoryName ? 'selected' : ''}>${productSubCategoryList}</option>
         </c:forEach>
        </select>
and the corresponding setting in request is like
for(int i=0;i<userProductData.size();i++){
    String productSubCategoryName=userProductData.get(i).getProductSubCategory();
    System.out.println(productSubCategoryName);
    request.setAttribute("productSubCategoryName",productSubCategoryName);

}
here i have multiple select drop down ,even though i get the return value from for as two ,in the UI only one data is getting higlighted not the second one,What is wrong in the code ?
解决方案
Assuming that you have a collection ${roles} of the elements to put in the combo, and ${selected} the selected element, It would go like this:
<select name='role'>
    <option value="${selected}" selected>${selected}</option>
    <c:forEach items="${roles}" var="role">
        <c:if test="${role != selected}">
            <option value="${role}">${role}</option>
        </c:if>
    </c:forEach>
</select>
UPDATE (next question)


You are overwriting the attribute "productSubCategoryName". At the end of the for loop, the last productSubCategoryName.

Because of the limitations of the expression language, I think the best way to deal with this is to use a map:
Map<String,Boolean> map = new HashMap<String,Boolean>();
for(int i=0;i<userProductData.size();i++){
    String productSubCategoryName=userProductData.get(i).getProductSubCategory();
    System.out.println(productSubCategoryName);
    map.put(productSubCategoryName, true);
}
request.setAttribute("productSubCategoryMap", map);
And then in the JSP:
<select multiple="multiple" name="prodSKUs">
    <c:forEach items="${productSubCategoryList}" var="productSubCategoryList">
        <option value="${productSubCategoryList}" ${not empty productSubCategoryMap[productSubCategoryList] ? 'selected' : ''}>${productSubCategoryList}</option>
    </c:forEach>
</select>


                        
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