myMap.get(myKey) with JSTL?

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Christine Mayer - 16 Oct 2007 11:06 GMT

Hi, I need to get a map entry based on a key - how can this be done
using the JSTL?

I know I could say:
<c:forEach items="${myMap }" var="entry" >
<c:if test="${entry.key== myKey }">
</c:if>
</c:forEach>

but this seems pretty stupid to me.

Any idea how to solve this?

Thanks in advance,

Christine

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Lew - 16 Oct 2007 14:14 GMT

> Hi, I need to get a map entry based on a key - how can this be done
> using the JSTL?
[quoted text clipped - 6 lines]
>
> but this seems pretty stupid to me.

"${ myMap [myKey] }"
or
"${ myMap.myKey }"

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Lew

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Christine Mayer - 16 Oct 2007 14:42 GMT

This works:
    <c:out value="${myKey}"/> Output: E.g. 4711
    <c:out value="${myMap}"/> Output: The content of the entire object

This however does not work(empty output):
    <c:out value="${myMap['4711']}"/>
    <c:out value="${myMap[myKey]}"/>
    <c:out value="${myMap.myKey}"/>
    <c:out value="${myMap.'4711'}"/>

myMap contains a String key and a bean as value. The bean encapsulates
a list (that contains other beans again), that I later want to iterate
over. What I would like to achieve is something like:
<c:set value="${myMap[myKey]}" var="myBean"/>
    <c:forEach items="${myBean.myList}" var="row">
    <c:out value="${row.myValue1}"/>
<c:out value="${row.myValue2}"/>
    <c:out value="${row.myValue3}"/>
    </c:forEach>

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Lew - 16 Oct 2007 14:52 GMT

> This works:
> <c:out value="${myKey}"/> Output: E.g. 4711
[quoted text clipped - 10 lines]
> over. What I would like to achieve is something like:
> <c:set value="${myMap[myKey]}" var="myBean"/>

Odd. According to
<http://java.sun.com/javaee/5/docs/tutorial/doc/bnahq.html#bnahv>

> To refer to properties of a bean or an Enum instance, items of a
> collection, or attributes of an implicit object,
> you use the . or [] notation, which is similar to the notation used by ECMAScript.

...

> In contrast, an item in a Map can be accessed using a string literal key; no coercion is required:
>
> ${customer.orders["socks"]}

... and
<http://java.sun.com/javaee/5/docs/tutorial/doc/bnahq.html#bnain>

> ${departments[deptName]}
> The value of the entry named deptName in the departments map.

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Lew

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Daniel Pitts - 16 Oct 2007 20:35 GMT

> This works:
> <c:out value="${myKey}"/> Output: E.g. 4711
[quoted text clipped - 15 lines]
> <c:out value="${row.myValue3}"/>
> </c:forEach>

what about ${myMap[4711]}?
If it is a String key, make sure that myKey is also a String.
Where does myKey come from? Might it be better to have whatever
constructs your model pull the value out of the map?

It should work the way you've tried, unless there is something else
going on.

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Christine Mayer - 17 Oct 2007 13:54 GMT

Finnally, it worked out - it turned out that "A" != "a"!!!!!!! ;-)

Thx, Christine

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Lew - 17 Oct 2007 15:01 GMT

> Finnally, it worked out - it turned out that "A" != "a"!!!!!!! ;-)

Was this something that turned up in a key comparison?

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Lew

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Daniel Pitts - 17 Oct 2007 15:22 GMT

> Finnally, it worked out - it turned out that "A" != "a"!!!!!!! ;-)
>
> Thx, Christine