For accessing dynamic value from hash map you can use brace notation []
.
${someMap[dynamicKey]}
For example, consider @Som's answer map
Map<String, String> countryMap = new HashMap<String, String>();
countryMap.put("United States", "Washington DC");
countryMap.put("India", "Delhi");
countryMap.put("Germany", "Berlin");
countryMap.put("France", "Paris");
countryMap.put("Italy", "Rome");
request.setAttribute("countryMap", countryMap);
JSP
Set key
<c:set var="keyName" value="India" />
pass the dynamic key
${countryMap[keyName]}
Or directly
${countryMap['United States']}
See also