如何在< c：forEach>中迭代嵌套的地图 [英] How to iterate over a nested map in <c:forEach>

问题描述

我在bean中有一个 Map ，如下所示：

  public class TaskListData {
 private Map< String，String []> srcMasks = new HashMap< String，String []>（）; 
 private Map< Integer，Map< String，String []>> ftqSet = new HashMap< Integer，Map< String，String []>>（）; 
 
 public void setFTQSet（Integer ftqid，String [] src，String [] masks）{
 srcMasks.put（srcDir，src）; 
 srcMasks.put（mask，masks）; 
 ftqSet.put（ftqid，srcMasks）; 
 
  

这个 ftqSet 适合在下面的数据结构：

  feedId =5，
 feedName =myFeedName，
 ftqSet = > {
 1 => {
 srcDirs = [/ path / string]，
 masks = [p.txt，q.csv] 
} 
 2 => {... 
} 
}，... 
  

在我的测试JSP文件我一直在使用< c：forEach> 来访问数据：

 < c：forEach items =＃{bean.ftqSet}var =f> 
本文不打印
 $ {f.feedId} 
< / c：forEach> 
  

但不会输出 $ {f.feedId} 。为什么会这样？我如何访问这个结构的单个元素，这样我就可以创建一个漂亮的表格了？

解决方案 Map 在 c：forEach 中给出 Map.Entry 实例，该实例又具有 getKey（） 和 getValue（） 方法。这与在普通Java中为（Entry entry：map.entrySet（））做类似。

p>

 < c：forEach items =＃{bean.map}var =entry> 
< h：outputText value =Key：＃{entry.key}，Value：＃{entry.value}/>< br /> 
< / c：forEach> 
  

如果 Map< Integer，Map< String，String [] >>< / code>< code>＃{entry.value} 返回一个 Map< String，String []> code>，所以你需要迭代它：

 < c：forEach items =＃ bean.map}var =entry> 
 < c：forEach items =＃{entry.value}var =nestedentry> 
 < / c：forEach>< br /> 
< / c：forEach> 
  

但在你的情况下，＃{nestedentry.value} 实际上是一个 String [] ，所以我们需要再次迭代它：



 < c：forEach items =＃{bean.map}var =entry> 
 < c：forEach items =＃{entry.value}var =nestedentry> 
 < c：forEach items =＃{nestedentry.value}var =nestednestedentry> 
< h：outputText value =＃{nestednestedentry}/> 
< / c：forEach>< br /> 
< / c：forEach>< br /> 
< / c：forEach> 
  

顺便说一句，这应该与 rich：dataList 。

I've a Map in a bean as follows:

public class TaskListData {
    private Map<String, String[]> srcMasks = new HashMap<String, String[]>();
    private Map<Integer, Map<String, String[]>> ftqSet = new HashMap<Integer, Map<String, String[]>>();

    public void setFTQSet(Integer ftqid, String[] src, String[] masks) {  
        srcMasks.put("srcDir", src);
        srcMasks.put("masks", masks);
        ftqSet.put(ftqid, srcMasks);
    }

This ftqSet fits in below datastructure:

feedId = "5",
feedName = "myFeedName",
ftqSet => {
            1 => {
                    srcDirs = ["/path/string"],
                    masks = ["p.txt", "q.csv"]
                 }
            2 => { ...
                 }
          }, ...

In my test JSP file I've been trying to access the data using <c:forEach>:

<c:forEach items="#{bean.ftqSet}" var="f">
    this text does not print
    ${f.feedId}
</c:forEach>

But it's not outputting ${f.feedId}. Why would this be? How would I access this structure's individual elements so I can create a nice table?

解决方案

Each iteration of Map in a c:forEach gives a Map.Entry instance which in turn has getKey() and getValue() methods. It's similar to doing for (Entry entry : map.entrySet()) in plain Java.

E.g.

<c:forEach items="#{bean.map}" var="entry">
    <h:outputText value="Key: #{entry.key}, Value: #{entry.value}" /><br />
</c:forEach>

In case of a Map<Integer, Map<String, String[]>> the #{entry.value} returns a Map<String, String[]>, so you need to iterate over it as well:

<c:forEach items="#{bean.map}" var="entry">
    <h:outputText value="Key: #{entry.key}, Values:" />
    <c:forEach items="#{entry.value}" var="nestedentry">
        <h:outputText value="Nested Key: #{nestedentry.key}, Nested Value: #{nestedentry.value}" />
    </c:forEach><br />
</c:forEach>

But in your case, the #{nestedentry.value} is actually a String[], so we need to iterate over it again:

<c:forEach items="#{bean.map}" var="entry">
    <h:outputText value="Key: #{entry.key}, Values:" />
    <c:forEach items="#{entry.value}" var="nestedentry">
        <h:outputText value="Nested Key: #{nestedentry.key}, Nested Values: " />
        <c:forEach items="#{nestedentry.value}" var="nestednestedentry">
            <h:outputText value="#{nestednestedentry}" />
        </c:forEach><br />
    </c:forEach><br />
</c:forEach>

By the way, this ought to work with rich:dataList as well.

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