There are a couple of mistakes.
- The factory method should be public.
- You're casting to "database" and not "Database".
Regards,
Subrahmanyam
Matthias Haberkorn wrote:
>
> Hello developers,
>
> hmm, I hope this is not a "long time discussed" problem!
> If so, please forgive me - I'm new to this mailinglist ;-)
> Ok, here is my problem:
> I have a class for accessing my database-routines with an
> instance like this:
> -------------------------
> public class Database
> {
> private static Database onlyInstance = null;
>
> /* Private no-args constructor */
> private Database() {
> init();
> }
>
> /** Private factory method (make a single instance of this
> class) */
> private static Database instance() {
> if (onlyInstance == null)
> onlyInstance = new Database();
> return onlyInstance;
> }
>
> /** Init (Connect to DB) */
> public void init()
> {
> try {....
> --------------------------
>
> ...and I have a servlet which tries to get an instance of this class:
>
> --------------------------
> public class testdb extends HttpServlet
> {
>
> /** Init the Servlet (get instance of db) */
> public void init() throws ServletException
> {
> Database database =
> (database)getServletContext().getAttribute("database");
>
> if (database == null) {
> getServletContext().setAttribute("database",
> database.instance() );
> }
> }
>
> public void doGet() {...
> --------------------------
>
> If I try to get the instance back in one of the doGet/Post-methods, I
> get a "ClassCastException" for Database. This is how I try to get the
> instance:
>
> --------------------------
> ....
> Database database =
> (Database)getServletContext().getAttribute("Database");
>
> ResultSet rs = database.getSomething(id);
> ....
> --------------------------
>
> It looks like that the getAttribute-methode doesn't give back a object
> of type Database. Or is there something complete wrong with that code ??
> (..or likely with my concept of interservlet-communication ??)
>
> I use a Linux box with the Blackdown-JDK 1.1.7v3 with a Jetty-Webserver.
> Thanks for all contributions to this question.
>
> bye
>
> MaZe
>
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--
-----------------------------------------------------------------------
Subrahmanyam A.V.B. Wipro Infotech (EC/FS)
Associate Consultant 1st Floor, Basappa Complex
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Fax: 91-80-2278597 Bangalore 560 001
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