Re: problem upgrading to JSTL 1.2

From:

Lew <lew@lewscanon.com>

Newsgroups:

comp.lang.java.programmer

Date:

Sun, 30 Dec 2007 11:26:43 -0500

Message-ID:

<S92dnUxeWPlbW-ranZ2dnUVZ_tijnZ2d@comcast.com>

yishayjobs@hotmail.com wrote:

The following jsp (I named it 'master.jsp') is as simple as I've
gotten it.

=====

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ page import="org.apache.struts.action.ActionMessage"%>
<%@ page import="org.apache.struts.action.ActionMessages"%>

<%! public class MyActionMessages extends ActionMessages {
        public java.util.Map getMessages() {
            return messages;
        }
}
%>

<%
    MyActionMessages actionMessages = new MyActionMessages();
         actionMessages.add("prop1", new ActionMessage("one"));
         session.setAttribute("my_action_message_item",
actionMessages.getMessages().get("prop1"));
%>
<html>
<body>
<span>this is a test: ${my_action_message_item.list}</span><br>
</body>
</html>

====

The message I get is:

org.apache.jasper.JasperException: An exception occurred processing
JSP page /views/profiler/master.jsp at line 20

...

root cause

javax.el.PropertyNotFoundException: Property 'list' not readable on
type java.util.List
    javax.el.BeanELResolver$BeanProperty.read(BeanELResolver.java:259)
    javax.el.BeanELResolver$BeanProperty.access$000(BeanELResolver.java:
209)
    javax.el.BeanELResolver.getValue(BeanELResolver.java:60)
    javax.el.CompositeELResolver.getValue(CompositeELResolver.java:53)
    org.apache.el.parser.AstValue.getValue(AstValue.java:97)
    org.apache.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:
186)

org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate(PageContextImpl.java:
923)
    org.apache.jsp.views.profiler.master_jsp._jspService(master_jsp.java:
77)

==========

This is after the upgrade (see my opening post). Before upgrade the
list is evaluated in the normal toString fasion. I get:

====

this is a test: [one[]]

The object retrieved via 'my_action_message_item' is the one from the call to

actionMessages.getMessages().get("prop1")

'actionMessages.getMessages()' is a Map, 'messages'. A raw Map.
'messages.get("prop1")' returns an Object. 'Object' does not have a method
'getList()'. Boom. But that's not the error. Somehow the system figured out
what the underlying Map types are. Let's follow that chain.

The retrieval from getMessages() is the protected 'messages' element of the
superclass, a HashMap that maps String to an ArrayList. So the result of
get("prop1") is an ArrayList<ActionMessage>.

You then call getList() on that ArrayList. But ArrayList doesn't have such a
method. Now boom.

The exception is correct behavior.

--
Lew