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I have a Map in EL as ${map} and I am trying to get the value of it using a key which is by itself also an EL variable ${key} with the value "1000".
Using ${map["1000"]} works, but ${map["$key"]} does not work. What am I doing wrong and how can I get the Map value using a variable as key?
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util. HashMap. get() method of HashMap class is used to retrieve or fetch the value mapped by a particular key mentioned in the parameter. It returns NULL when the map contains no such mapping for the key.
Key value maps (KVMs) are ideal for this. A KVM is a custom collection of encrypted key/value String pairs. The following lists three broad use cases for storing data in KVMs: User session data: Data that is created and deleted by the runtime only; you cannot view or manage KVM entries outside of the runtime.
put() method of HashMap is used to insert a mapping into a map. This means we can insert a specific key and the value it is mapping to into a particular map. If an existing key is passed then the previous value gets replaced by the new value. If a new pair is passed, then the pair gets inserted as a whole.
$ is not the start of a variable name, it indicates the start of an expression. You should use ${map[key]} to access the property key in map map.
You can try it on a page with a GET parameter, using the following query string for example ?whatEver=something
<c:set var="myParam" value="whatEver"/>
whatEver: <c:out value="${param[myParam]}"/>
This will output:
whatEver: something
See: https://stackoverflow.com/tags/el/info and scroll to the section "Brace notation".
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