在 h:dataTable 中使用 java.util.Map [英] Using java.util.Map in h:dataTable

问题描述

我需要使用 显示 Map.我的支持 bean 有一个 Map 属性，如下所示:

I need to display Map using <h:dataTable>. My backing bean has a Map property as below:

public class Bean {

    private Map<Integer,String> map; // +getter

    @PostConstruct
    public void init() {
        map = new TreeMap<Integer,String>();
        map.put(1,"Sasi");
        map.put(2,"Pushparaju");
        map.put(3,"Venkat Raman");
        map.put(3,"Prabhakaran");
    }

}

然后在 JSF 页面中，我尝试将此 Map 属性绑定到 的 value 属性.

Then in JSF page I am trying to bind this Map property to the value attribute of <h:dataTable>.

 <h:dataTable border="1" value="#{bean.map}" var="map">
    <h:column id="column1">
        <f:facet name="header">
            <h:outputText value="UserId"></h:outputText>
        </f:facet>
        <h:outputText value="#{map.getKey}"></h:outputText>
    </h:column>
    <h:column id="column2">
        <f:facet name="header">
            <h:outputText value="Email Id"></h:outputText>
        </f:facet>
        <h:outputText value="#{map.getValue}"></h:outputText>
    </h:column>
</h:dataTable>

它给出了 getKey 和 getValue 不存在的错误.我可以理解这不是正确的方法.如何使用 呈现 Map?

It is giving en error that getKey and getValue is not present. I can understand that this is not the correct way to do it. How can I present a Map using <h:dataTable>?

推荐答案

直到即将到来的 JSF 2.3，UIData 组件如 、<p:dataTable> 等，并且 确实不支持对 Map 进行迭代.这仅在 中受支持.

Until upcoming JSF 2.3, UIData components such as <h:dataTable>, <p:dataTable>, etc and <ui:repeat> does not support iterating over a Map. This is only supported in <c:forEach>.

一种方法是将地图条目转换为数组(单独的 entrySet() 将不起作用，因为 UIData 也不支持 Set 直到即将到来的 JSF 2.3).

One way is to convert the map entries to an array (alone entrySet() won't work as UIData also doesn't support Set until upcoming JSF 2.3).

<h:dataTable value="#{bean.map.entrySet().toArray()}" var="entry">
    <h:column>#{entry.key}</h:column>
    <h:column>#{entry.value}</h:column>
</h:dataTable>

另一种方法是将地图的条目集合包装在 可以迭代的集合中，例如 ArrayList.

Another way is to wrap the map's entry set in a collection which the <h:dataTable> can iterate over, such as an ArrayList.

public class Bean {

    private Map<Integer, String> map;
    private List<Entry<Integer, String>> entries; // +getter (no setter necessary)

    @PostConstruct
    public void init() {
        map = new TreeMap<>();
        map.put(1, "Sasi");
        map.put(2, "Pushparaju");
        map.put(3, "Venkat Raman");
        map.put(4, "Prabhakaran");
        entries = new ArrayList<>(map.entrySet());
    }

    // ...
}

<h:dataTable value="#{bean.entries}" var="entry">
    <h:column>#{entry.key}</h:column>
    <h:column>#{entry.value}</h:column>
</h:dataTable>

然而，更干净、自我记录和可重用的是使用 List 代替，其中 User 类具有必要的属性 id 和 name.

However, more clean, self documenting and reusable is to use a List<User> instead wherein the User class has the necessary properties id and name.

public class Bean {

    private List<User> users; // +getter (no setter necessary)

    @PostConstruct
    public void init() {
        users = new ArrayList<>();
        users.add(new User(1, "Sasi"));
        users.add(new User(2, "Pushparaju"));
        users.add(new User(3, "Venkat Raman"));
        users.add(new User(4, "Prabhakaran"));
    }

    // ...
}

<h:dataTable value="#{bean.users}" var="user">
    <h:column>#{user.id}</h:column>
    <h:column>#{user.name}</h:column>
</h:dataTable>

这篇关于在 h:dataTable 中使用 java.util.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！