Solved

ClassCastException Error

Posted on 2003-12-03
15
297 Views
Last Modified: 2010-03-31
I get the ClassCastException for the line below:

String settingsClass = config.getInitParameter("SettingsClass");
                  
Settings settings = (Settings) Class.forName(settingsClass).newInstance(); //<-- this is where the exception error occurs

Thanks for the help!
0
Comment
Question by:ericworldz
  • 6
  • 5
  • 2
  • +1
15 Comments
 
LVL 86

Expert Comment

by:CEHJ
ID: 9867264
Split those bits up and test it.
0
 
LVL 35

Expert Comment

by:TimYates
ID: 9867283
The class defined by "settingsClass" does not extend or implement "Settings"

Try

System.out.println( settingsClass ) ;

before you do the Class.forName

I reckon it's "null"
0
 
LVL 16

Expert Comment

by:imladris
ID: 9867285
The nature of the exception indicates that the forName method is picking up a class, then newInstance is creating an instance of it, but it isn't a class of type Settings, so when it tries to cast it to a class of that type, it throws an exception.

I'm guessing that you are expecting it to be a class of type Settings. If so, perhaps you could print out the string you are getting from the getInitParameter call (System.out.println("class name: "+settingsClass);), and post the code (at least the class definition and the constructor) of the class you are trying to load.
0
Free Tool: IP Lookup

Get more info about an IP address or domain name, such as organization, abuse contacts and geolocation.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

 
LVL 16

Expert Comment

by:imladris
ID: 9867294
The three musketeers strike again  :)
0
 
LVL 35

Expert Comment

by:TimYates
ID: 9867333
:-D
0
 
LVL 86

Expert Comment

by:CEHJ
ID: 9867340
>>I reckon it's "null"

So do I
0
 

Author Comment

by:ericworldz
ID: 9867400
I try to print out the settingsClass and it's not null.
It returns settingsClass=com.goals.Site, so I guess when I try to cast it to Settings it gives me the ClassExceptionError.

Below is the code for the Settings class:
public interface Settings {
public Site getSite(Hashtable initParams) throws Exception;      
}

So what is the way to get around this?
Thanks!
0
 
LVL 35

Expert Comment

by:TimYates
ID: 9867432
package com.goals ;

public class Site implements Settings
0
 
LVL 35

Expert Comment

by:TimYates
ID: 9867433
make sure it implements "Settings" :-)
0
 
LVL 86

Expert Comment

by:CEHJ
ID: 9867466
T's always a good idea to type-check anyway

Object o = Class.forName(settingsClass).newInstance();
if (o instanceof Settings) {
     Settings s = (Settings)o;
}
0
 
LVL 35

Expert Comment

by:TimYates
ID: 9867479

else {
    log.fatal( o + " IS NOT A SETTINGS OBJECT!" ) ;
}
0
 

Author Comment

by:ericworldz
ID: 9867589
It is implementing Settings
0
 
LVL 35

Accepted Solution

by:
TimYates earned 50 total points
ID: 9867621
can you post the code for the Site class?

It's either in the wrong package, or implementing the wrong settings class or something...

Do you only have one Settings class/interface?

try putting the full classname in the cast:

com.goals.Settings settings = (com.goals.Settings)Class.forName( settingsClass ).newInstance() ;

does "Site" have an empty constructor?
0
 
LVL 86

Expert Comment

by:CEHJ
ID: 9867656
>>does "Site" have an empty constructor?

Must have, or couldn't be non-null ;-) (according to eric)
0
 
LVL 86

Expert Comment

by:CEHJ
ID: 9867748
Please, for the benefit of others, explain what the solution to the problem was eric
0

Featured Post

Free Tool: Postgres Monitoring System

A PHP and Perl based system to collect and display usage statistics from PostgreSQL databases.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
hibernate insert example 13 34
going to wrong jsp page 2 33
Java: The Public Class Main 4 32
What browser will run Java? 7 59
Java had always been an easily readable and understandable language.  Some relatively recent changes in the language seem to be changing this pretty fast, and anyone that had not seen any Java code for the last 5 years will possibly have issues unde…
Java functions are among the best things for programmers to work with as Java sites can be very easy to read and prepare. Java especially simplifies many processes in the coding industry as it helps integrate many forms of technology and different d…
Viewers learn about the “for” loop and how it works in Java. By comparing it to the while loop learned before, viewers can make the transition easily. You will learn about the formatting of the for loop as we write a program that prints even numbers…
Viewers will learn about if statements in Java and their use The if statement: The condition required to create an if statement: Variations of if statements: An example using if statements:

860 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question