I got around my problem using reflection:
Context initCtx = new InitialContext();
Context envCtx = (Context) initCtx.lookup("java:comp/env");
java.lang.Object object = envCtx.lookup("userDatabase");
// This throws ClassCastException
System.out.println("Database id " + ((UserDatabase)object).getId());
// This works
java.lang.reflect.Method m = object.getClass().getMethod("getId", null);
System.out.println("Database id " + m.invoke(object, null));
But is this the best way? The comment in server.xml saying "The database
object could be accessed like this:" suggests at least that the developer
who wrote the comment expected the cast to work.
-----Original Message-----
From: Danielle Mortimer
Sent: Tuesday, November 25, 2003 11:04 AM
To: '[EMAIL PROTECTED]'
Subject: ClassCastException trying to access UserDatabase from examples web
app
I am getting a ClassCastException when I try to access the global
UserDatabase from a web app. I believe it is something to do with different
class loaders but I'm not sure how to solve it. I noticed an old post on
this same topic
http://www.mail-archive.com/[EMAIL PROTECTED]/msg88967.html but
there was no response.
Details:
1. Out of the box Tomcat 4.1.29 install. Using Sun JDK 1.4.1_03. Windows
2000.
2. Modified server.xml to remove the comments around the ResourceLink in the
examples context:
<!-- If you wanted the examples app to be able to edit the
user database, you would uncomment the following entry.
Of course, you would want to enable security on the
application as well, so this is not done by default!
The database object could be accessed like this:
Context initCtx = new InitialContext();
Context envCtx = (Context) initCtx.lookup("java:comp/env");
UserDatabase database =
(UserDatabase) envCtx.lookup("userDatabase");
-->
<ResourceLink name="userDatabase" global="UserDatabase"
type="org.apache.catalina.UserDatabase"/>
3. Created jakarta-tomcat-4.1.29\webapps\examples\test.jsp using the sample
code from server.xml:
<%@ page import="javax.naming.*" %>
<%@ page import="org.apache.catalina.UserDatabase" %>
<html>
<body>
<%
Context initCtx = new InitialContext();
Context envCtx = (Context) initCtx.lookup("java:comp/env");
java.lang.Object object = envCtx.lookup("userDatabase");
out.write( "Database id " + ((UserDatabase)object).getId());
%>
</body>
</html>
4. Copied UserDatabase.class from
jakarta-tomcat-4.1.29\server\lib\catalina.jar into
jakarta-tomcat-4.1.29\webapps\examples\WEB-INF\classes\org\apache\catalina\U
serDatabase.class so the jsp will compile.
5. Restart Tomcat.
6. Go to http://localhost:8080/examples/test.jsp, browser displays
exception:
org.apache.jasper.JasperException
at
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:2
54)
...
root cause
java.lang.ClassCastException
at org.apache.jsp.test_jsp._jspService(test_jsp.java:51)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:137)
...
Thanks in advance for any suggestions.
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