Afterthat i worked without this Error: No source files and no packages been specified error.
<body>
<%@taglib uri='../WEB-INF/core-jstl.tld' prefix='core-jstl' %>
<font size='5'>Request Parameters: </font>
<p><core-jstl:showMap map='${param}'/></p>
<font size='5'>Request Headers:</font>
<p><core-jstl:showMap map='${header}'/></p>
<font size='5'>Cookies:</font>
<p><core-jstl:showMap map='${cookie}'/></p>
</body>
SEVERE: Servlet.service() for servlet jsp threw exception
javax.servlet.jsp.JspException: An error occurred while evaluating custom action attribute "map" with value "org.apache.commons.el.ImplicitObjects$5@1b34126": Attempt to convert String "org.apache.commons.el.ImplicitObjects$5@1b34126" to type "java.util.Map", but there is no PropertyEditor for that type (null)
at org.apache.taglibs.standard.lang.jstl.Evaluator.evaluate(Evaluator.java:109)
at org.apache.taglibs.standard.lang.jstl.Evaluator.evaluate(Evaluator.java:129)
at org.apache.taglibs.standard.lang.support.ExpressionEvaluatorManager.evaluate(ExpressionEvaluatorManager.java:75)
at code.tag.ShowMapAction.doStartTag(ShowMapAction.java:24)