JSP 2.0 expression Language - Implicit Objects
This example illustrates some of the implicit objects available in the expression Lanaguage. The following implicit objects are available (not all illustrated here):

    * pageContext - the PageContext object
    * pageScope - a Map that maps page-scoped attribute names to their values
    * requestScope - a Map that maps request-scoped attribute names to their values
    * sessionScope - a Map that maps session-scoped attribute names to their values
    * applicationScope - a Map that maps application-scoped attribute names to their values
    * param - a Map that maps parameter names to a single String parameter value
    * paramValues - a Map that maps parameter names to a String[] of all values for that parameter
    * header - a Map that maps header names to a single String header value
    * headerValues - a Map that maps header names to a String[] of all values for that header
    * initParam - a Map that maps context initialization parameter names to their String parameter value
    * cookie - a Map that maps cookie names to a single Cookie object.

    Change Parameter
    foo =

    EL expression    Result ${param.foo}    <script>alert()</script></A>
    ${param["foo"]}    <script>alert()</script></A>
    ${header["host"]}     x-sons.com.ar:8080
    ${header["accept"]}    text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
    ${header["user-agent"]}    Mozilla/5.0 (Windows; U; Windows NT 6.0; es-ES; rv:1.9.1.9) Gecko/20100315 Firefox/3.5.9 (.NET CLR 3.5.30729)