ui:repeat 不适用于 Map [英] ui:repeat doesn't work with Map
问题描述
我有一个键/值的 Map，我在 @PostConstruct 中初始化如下:
I have a Map of key / values, which I initialize in @PostConstruct as follows:
Map<String, String> myMap;
@PostConstruct
public void init() {
myMap=new LinkedHashMap<String, String>();
myMap.put("myKey","myValue");
}
public Map<String, String> getMyMap() {
return myMap;
}
public void setMyMap(Map<String, String> myMap) {
this.myMap = myMap;
}
当我尝试使用 <ui:repeat> 迭代这个 Map 时，如下所示，并且我在 Map 的 getter 上设置了一个断点，我注意到它没有被调用，所以没有打印任何内容:
When I try to iterate over this Map with <ui:repeat> like shown bellow, and I set a break point on the getter for the Map, I notice that it is not getting called, and so nothing is printed:
<ice:panelGroup>
<ui:repeat items="#{myBean.myMap}" var="entry" varStatus="loop">
<input type="checkbox" name="myCheckBoxes" value="#{entry.value}" />
<span class="#{fn:contains(entry.value,'g') ? 'bold-style' : ''}">#{entry.key}</span>
</ui:repeat>
</ice:panelGroup>
但是当用 <c:foreach> 替换上面的代码时，一切正常，并且列表按预期打印，为什么我会出现这种行为?
But when replacing above code with <c:foreach>, everything works fine, and the list is printed as expected, any ideas why I am getting such behavior?
推荐答案
更新: JSF 2.3(自 2017 年起)支持此 开箱即用.
UPDATE: JSF 2.3 (since 2017) supports this out of the box.
遗憾的是，UIData 和 UIRepeat 不支持在 JSF 中遍历地图.
Unfortunately, UIData and UIRepeat have no support for iterating over a map in JSF.
如果这让您感到困扰(我猜是这样)，请为以下问题投票，如果可能，请发表评论以解释您对此的看法:
If this bothers you (I guess it does), please vote for the following issue and if possible leave a comment that explains how you feel about this:
http://java.net/jira/browse/JAVASERVERFACES_SPEC_PUBLIC-479
与此同时，您可以使用一些小助手代码遍历 Map:
In the mean time, you can iterate over a Map with some little helper code:
/**
* Converts a Map to a List filled with its entries. This is needed since
* very few if any JSF iteration components are able to iterate over a map.
*/
public static <T, S> List<Map.Entry<T, S>> mapToList(Map<T, S> map) {
if (map == null) {
return null;
}
List<Map.Entry<T, S>> list = new ArrayList<Map.Entry<T, S>>();
list.addAll(map.entrySet());
return list;
}
然后在 *-taglib.xml 文件中定义一个 EL 函数，如下所示:
Then define an EL function in a *-taglib.xml file like this:
<namespace>http://example.com/util</namespace>
<function>
<function-name>mapToList</function-name>
<function-class>com.example.SomeClass</function-class>
<function-signature>java.util.List mapToList(java.util.Map)</function-signature>
</function>
最后像这样在 Facelet 上使用它:
And finally use it on a Facelet like this:
<html xmlns:util="http://example.com/util">
<ui:repeat value="#{util:mapToList(someDate)}" var="entry" >
Key = #{entry.key} Value = #{entry.value} <br/>
</ui:repeat>
这篇关于ui:repeat 不适用于 Map的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
