[ Servlet ] Error when I added the init() method to a servlet

[Pho Tek]

Context
IBM VAJ WTE environment
Problem
I wrote a servlet and it is working fine.
I then needed the servlet to read some
parameters and to persist them to the
application scope. The servlet compiled fine.
But when the servlet is loaded, I get this
error on my browser:
Server caught unhandled exception from servlet [FooServlet]: null
My init method looks something like this:

public void init(ServletConfig config) throws javax.servlet.ServletException {
    int pageSize = 0;
String x = config.getInitParameter("pageSize");
    if (x == null)
    throw new ServletException( this.getClass().getName() + ": no pageSize parameter was specified" );
    try{
     
    pageSize = Integer.parseInt(x);    
        if (pageSize < 1) throw new IllegalArgumentException("pageSize must be 1 or higher");
         
}catch(NumberFormatException nfe){
    throw new ServletException( this.getClass().getName() + ": pageSize parameter must be numeric" );
    }catch(IllegalArgumentException iae){
    throw new ServletException( this.getClass().getName() + ": pageSize needs to be 1 or higher" );    
    }    
    System.out.println("pageSize = " + pageSize);
    // add to the context
    ServletContext sc = config.getServletContext();
    sc.setAttribute("FAS_controller", new Integer(pageSize));
}

Can anyone help me out ?
Thanks
Pho

[Craig Jackson]

I think the problem is that if pageSize < 1 you will throw an IllegalArgumentException() at that point processing stops, the exception will not be caught by the "IllegalArgumentException" catch phrase, so the method signature of the init() method has to specify the
IllegalArgumentException in the throws clause.
Craig

[Craig Jackson]

But, I think it would be more correct if you changed the code to:

 if (pageSize < 1) throw new ServletException( this.getClass().getName() + ": pageSize needs to be 1 or higher" );

Any other suggestions.
Craig

[Anthony Villanueva]

I tried your code with Tomcat 3.2 and yes I'm getting a

javax.servlet.ServletException: PhotekServlet: (error) no pageSize parameter was specified
at PhotekServlet.init(PhotekServlet.java:13)
at javax.servlet.GenericServlet.init(GenericServlet.java:258)

(Yes, I named it after you. )
The occurs when I access it with
http://anthony:8080/myContext/servlet/PhotekServlet
but it disappears when I use
http://anthony:8080/myContext/servlet/photek
where "photek" is the servlet alias of PhotekServlet. It also works when you have an explicit servlet mapping.
-anthony

[Pho Tek]

Hey guys,
I've rewritten the init method to look like this, and it's working fine.

  
public void init(ServletConfig config) throws javax.servlet.ServletException {
    super.init(config); //1
    
    try{
        int pageSize = 0;
    String x = config.getInitParameter("pageSize");   
        pageSize = Integer.parseInt(x);    
        if (pageSize < 1) throw new Exception();
    // add to the context
        ServletContext sc = config.getServletContext();
        sc.setAttribute("FAS_pageSize", new Integer(pageSize));
        System.out.println("pageSize = " + pageSize);
         
}catch(Throwable t){
    throw new ServletException( this.getClass().getName() + ": pageSize parameter is mandatory, must be numeric and bigger than 1 in value." );
    }    
}

The changes made:
* In the line marked 1, I made a call to the superclass's init method. I read that if you're going to override the init, this is something which needs to be done. Why ? I don't know.
* I've dispensed with all the exceptions by rolling up the exceptions into one catch-all because that simplifies the code.
Pho
[ April 06, 2002: Message edited by: Pho Tek ]

[William Brogden]

In the line marked 1, I made a call to the superclass's init method. I read that if you're going to override the init, this is something which needs to be done. Why ? I don't know.

Simple, thats the only way to attach the configuration information to your servlet. If you don't do that you get mysterious null pointer exceptions later.
Your problem with different behaviour when addressing the servlet different ways is related to the information in web.xml. If you don't use the web.xml alias, the servlet does not get init-params from web.xml.
Bill