Re: Why is Java lying?

From:
Thomas Fritsch <i.dont.like.spam@invalid.com>
Newsgroups:
comp.lang.java.programmer
Date:
Tue, 28 Nov 2006 17:12:41 GMT
Message-ID:
<newscache$4hag9j$xe9$1@news.ops.de>
laredotornado@zipmail.com wrote:

I'm trying to compile a very simple JSP page on Tomcat 5.5, JDK 1.5

<%@ page import="java.util.*" %>
<%
   Object v = new String("b");
   session.setAttribute("a", v);

   Enumeration e = session.getAttributeNames();
   while (e.hasMoreElements()) {
       String attr = (String) e.nextElement();
       String v1 = session.getAttribute(attr);
       String v2 = session.getValue(attr);

I suspect the JSP compiler complains about the line above, because
HttpSession.getValue is declared as
    public Object getValue(String name)
but not as
    public String getValue(String name)
See
<http://java.sun.com/j2ee/1.4/docs/api/javax/servlet/http/HttpSession.html>.

       out.println("attr: " + attr + " v1:" + v1 + " v2:" + v2);
   } // while
%>

but I'm getting this compile error:

An error occurred at line: 2 in the jsp file: /session_vars.jsp
Generated servlet error:
Type mismatch: cannot convert from Object to String

An error occurred at line: 2 in the jsp file: /session_vars.jsp
Generated servlet error:
Type mismatch: cannot convert from Object to String

    org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:512)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:377)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:802)

First off, the line number is incorrect (line 2 is "<%") but more
importantly, I thought String extended Object.

Don't ask me why the compiler says "line: 2", although it actually seems
to be line 10.

Any thoughts? - Dave


--
Thomas

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