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< h：dataTable> 显示 Map 。我的支持bean有一个 Map 属性如下：

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页面中我正在尝试将映射属性绑定到值属性< h：dataTable> 。

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>

它给出了错误， getKey 和 getValue 不存在。我可以理解，这不是正确的方法。如何使用< h：dataTable> 提交地图？

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< h：dataTable> / code>，< p：dataTable> 等和< ui：repeat> 强>不支持迭代地图。这仅在< c：forEach> 中支持。

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 entrySet（）将不起作用 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含在集合中，这个集合中 ; h：dataTable> 可以迭代，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用户> 代替，其中用户类具有必需的属性 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>

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