如何从 f:selectItems 获取标签和值 [英] How to get both label and value from f:selectItems

问题描述

我正在处理一个 JSF 页面，该页面具有基于 List 的下拉列表:

I am working on a JSF page which has a dropdown based on List<SelectItem>:

<h:selectOneMenu value="#{bean.selectedItem}">
    <f:selectItems value="#{bean.availableItems}" />
</h:selectOneMenu>

我需要获取两者当前所选项目的值和标签.现在我只得到价值.我如何才能获得标签?

I need to get both the value and label of the currently selected item. Right now I only get the value. How can I get the label, too?

推荐答案

你不能.这就是 HTML 的工作原理.您知道，JSF 是一个 HTML 代码生成器.JSF 生成 HTML .HTML 元素将只发送所选 元素的 value 属性.它不会发送它的标签.

You can't. That's just how HTML works. You know, JSF is a HTML code generator. The JSF <h:selectOneMenu> generates a HTML <select><option> . The HTML <select> element will only send the value attribute of the selected <option> element. It will not send its label.

但这应该不是什么大问题.你已经知道服务器端的值和标签，在#{bean.availableItems}中.获取关联标签所需要做的就是通过值作为键来获取它.我建议把它做成一个 Map 反过来也可以在 f:selectItems 中使用.

But that shouldn't be a big issue. You namely already know both the value and label in the server side, inside the #{bean.availableItems}. All you need to do to get the associated label is to get it by the value as key. I suggest to make it a Map which in turn can also be used in f:selectItems.

基本开球示例:

public class Bean {
    private String selectedItem; // +getter +setter
    private Map<String, String> availableItems; // +getter

    public Bean() {
        availableItems = new LinkedHashMap<String, String>();
        availableItems.put("value1", "label1");
        availableItems.put("value2", "label2");
        availableItems.put("value3", "label3");
    }

    public void submit() {
        String selectedLabel = availableItems.get(selectedItem);
        // ...
    }
}

与

<h:selectOneMenu value="#{bean.selectedItem}">
    <f:selectItems value="#{bean.availableItems.entrySet()}" var="entry"
        itemValue="#{entry.key}" itemLabel="#{entry.value}" />
</h:selectOneMenu>

结果

<p>Selected label is #{bean.availableItems[bean.selectedItem]}</p>

另一种方法是将名称和值都包装在表示实体的 javabean 对象中，并通过转换器将整个对象设置为值.

An alternative is to wrap both name and value in a javabean object representing an entity and set the whole object as value, via a converter.

• 我们的selectOneMenu wiki 页面
• 如何填充选项h:selectOneMenu 从数据库?

• Our selectOneMenu wiki page
• How to populate options of h:selectOneMenu from database?

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