How to iterate over a nested map in <c:forEach>

foreach, hashmap, jsp, jstl

Solution

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.

Problem

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?

Original source