Re: JSTL: getting a map's keys

Lew <>
Mon, 19 Mar 2012 12:57:42 -0700 (PDT)
On Monday, March 19, 2012 11:15:52 AM UTC-7, Chris Riesbeck wrote:

Can anyone help me figure out why the following is happening, or further
experiments I can run? (I have workarounds but I'd like to know what I'm

   - SimTable, a subclass of HashTable [sic] that defines getKeys() to call

If you mean 'java.util.Hashtable', that's a rather obsolete class. You should stick with 'java.util.HashMap'.


Joshua Bloch recommends to prefer composition over inheritance.

   - a session variable "data" which is a HashTable with "rates" set to
an instance of a SimTable

If "rates" is set to an instance of a 'HashTable', or whatever, is 'data' then a 'Map<String,Map<?,?>>'?

Why does ${rates.keys} generate nothing in these lines of JSP?

How about you follow the advice here:
and then maybe we can help you. It would make it easier for you to answer the questions I'm asking.

I think perhaps you're overthinking the session vars. Why can't your 'rates' Map go in there directly?

   <c:set var="rates" value='${data["rates"]}'/>

rates: ${rates}</p>

jstl: ${rates.keys}</p>

jsp: <%= ((edu.northwestern.ils.simulator.SimTable)
pageContext.findAttribute("rates")).getKeys() %></p>

Here's the generated HTML output:

rates: {Bill=100.0, Fred=75.0, Jane=75.0, Mary=50.0, Sam=75.0,

jstl: </p>

jsp: [Bill, Fred, Jane, Mary, Sam, Sarah]</p>

Your example code is fragmented and incomplete. Give us something we can work with, please.


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