How to iterate an ArrayList inside a HashMap using JSTL?

java jsp map arraylist jstl

62,644

Solution 1

You can use JSTL <c:forEach> tag to iterate over arrays, collections and maps.

In case of arrays and collections, every iteration the var will give you just the currently iterated item right away.

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>

<c:forEach items="${collectionOrArray}" var="item">
    Item = ${item}<br>
</c:forEach>

In case of maps, every iteration the var will give you a Map.Entry object which in turn has getKey() and getValue() methods.

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>

<c:forEach items="${map}" var="entry">
    Key = ${entry.key}, value = ${entry.value}<br>
</c:forEach>

In your particular case, the ${entry.value} is actually a List, thus you need to iterate over it as well:

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>

<c:forEach items="${map}" var="entry">
    Key = ${entry.key}, values = 
    <c:forEach items="${entry.value}" var="item" varStatus="loop">
        ${item} ${!loop.last ? ', ' : ''}
    </c:forEach><br>
</c:forEach>

The varStatus is there just for convenience ;)

To understand better what's all going on here, here's a plain Java translation:

for (Entry<String, List<Object>> entry : map.entrySet()) {
    out.print("Key = " + entry.getKey() + ", values = ");
    for (Iterator<Object> iter = entry.getValue().iterator(); iter.hasNext();) {
        Object item = iter.next();
        out.print(item + (iter.hasNext() ? ", " : ""));
    }
    out.println();
}

Solution 2

Did you try something like this?

<c:forEach var='item' items='${map}'>
    <c:forEach var='arrayItem' items='${item.value}' />
      ...
    </c:forEach>
</c:forEach>

Solution 3

you haven't closed c tag.try out this

 <c:forEach items="${logMap}" var="entry">
        Key = ${entry.key}, values = 
        <c:forEach items="${entry.value}" var="item" varStatus="loop">
            ${item} ${!loop.last ? ', ' : ''}
        </c:forEach><br>
    </c:forEach>

62,644

Author by

Rakesh Juyal

Actively seeking new opportunities.

Updated on January 11, 2020

Comments

Rakesh Juyal over 4 years
I have a map like this,
```
Map<Integer,ArrayList<Object>> myMap = new LinkedHashMap<Integer,ArrayList<Object>>();
```
Now I have to iterate this Map and then the ArrayList inside the map. How can I do this using JSTL?
Powerlord over 14 years

And of course, you might want to output ${item.key} between the two foreach statements.
Rakesh Juyal over 14 years

i like the way u used '${!loop.last ? ', ' : ''}' :D
BalusC over 14 years

You can find more methods here: java.sun.com/products/jsp/jstl/1.1/docs/api/javax/servlet/js‌p/… The ${loop.index}, ${loop.first} and ${loop.last} are most useful here.
Dzung Nguyen over 12 years

yay ! Thanks for this post. This matches exactly my case which uses map.value as a list :)
MrRaymondLee over 10 years

<c:forEach> should be terminated by </c:forEach>
Edward J Beckett over 10 years

Elvis has left the building ?:
Admin about 10 years

@BalusC I also have similar question here on the JSTL stuff. See if you can help me out.. Any help will be appreciated.