JavaBeat Sample Question

[deepa raj]

Given the deployment descriptor for a Web Application is

<web-app version="2.4">

    <servlet>
        <servlet-name>InitParamsServlet</servlet-name>
        <servlet-class>scwcd14.chap02.InitParamsServlet</servlet-class>
    </servlet>
 

    <servlet-mapping>
        <servlet-name>InitParamsServlet</servlet-name>
        <url-pattern>/InitParamsServlet</url-pattern>
        
        <init-param>
            <param-name>name</param-name>
            <param-value>javabeat</param-value>
        </init-param>
 
    </servlet-mapping>
 
</web-app>

What will be the output of the following Servlet?

package scwcd14.chap02;
 
import java.io.*;
import java.net.*;
 
import javax.servlet.*;
import javax.servlet.http.*;
 
public class InitParamsServlet extends HttpServlet {
    
    public void init(){
        
        ServletConfig config = getServletConfig();
        System.out.println(config.getInitParameter("name"));
        System.out.println(config.getInitParameter("no-name"));
    }  
    ...
}

1. The Servlet will output 'javabeat null' in the Server Console.
2. The Servlet will fail to load as the init param property 'no-name' is not mentioned in the deployment descriptor.
3. A NullPointerException will be raised as calling getServletConfig() in the init() method will return a null reference. 

[sudhakar karnati]

Answer is 1. The Servlet will output 'javabeat null' in the Server Console.

Thanks & Regards,
Sudhakar Karnati

[Ramesh Ponnada]

init-param tag is part of <servlet> not <servlet-mapping>

So, above code will print 2 nulls.

[Jan Sterk]

Originally posted by Ramesh Ponnada:
init-param tag is part of <servlet> not <servlet-mapping>

So, above code will print 2 nulls.

Good point!!

[sudhakar karnati]

Answer is 1. The Servlet will output 'javabeat null' in the Server Console.

I ran the above example in Netbeans.and its extra features made me this mistake.

Thanks
Sudhakar

[Savyatha Reddy]

so, is the above code gives an output of "javabeat null" OR "null null"

[Prasad Tamirisa]

so, is the above code gives an output of "javabeat null" OR "null null"

Its very clear. The Answer is null null

[Srividhya Kiran]

Hello

I think we get a compile time error by declaring <init-param> as a subelement of <servlet-mapping>. I am using eclipse and it gives me a error if I give <init-param> under <servlet-mapping> element.

Srividhya

[Ramesh Ponnada]

IDEs like eclipse, netbeans can have schema validation enabled.
Because init-param is not a part of servlet-mapping it schema validation fails and eclipse reports it as a error in the problems view.
(one can disable the validations in the eclipse preferences)


Also, if you have XML-Validation turned on in the container(I am taking about Tomcat, I don't know how to do it in others) web application won't start/load.
[ August 11, 2008: Message edited by: Ramesh Ponnada ]