Multiple users, closed connections

Question

Hi,
I have been building this web application for some time now, and it's going through testing right now. This project has pretty much been a foray into the world of Java/JSP/JDBC/JNDI/etc, considering I've been learning as I go. But - the second the test group actually started using the application, they got random errors. According to the logs, connection closed errors.
The scenario looks something like this (according to the logs):
Client A opens a page
Client B opens a page
Client B finishes faster and connection closes
Client A gets SQLException: Connection is closed.
It's as if there is only one connection (..is there? Truth be told, I'm not exactly sure). I was thinking that it may be a race condition, something to do with threads (although I don't use threads myself, I was just guessing Tomcat might have something to do with this) or something to do with Tomcat's cache, but it's hard to start poking around without knowing what I should poke. I'm betting my money on the all-time favourite - PEBKAC.
Anyway, the application has a "base" JSP, which in turn loads other classes if necessary.
The JSP contains:
/* 8< 8< 8< 8< 8< 8< */
db=new DBconnection("jdbc/mydb");
/* 8< 8< 8< 8< 8< 8< */
db.Close();Configuration file:
<Resource name="jdbc/mydb" auth="Container" type="javax.sql.DataSource"/>
<ResourceParams name="jdbc/mydb">
</ResourceParams>
/* 8< 8< 8< 8< 8< 8< */
<parameter>
<name>driverClassName</name>
<value>com.mysql.jdbc.Driver</value>
</parameter>
<parameter>
<name>url</name>
<value>jdbc:mysql://localhost:3306/mydb?autoReconnect=true</value >
</parameter>The DBconnection class outline:
public final class DBconnection {
  private Connection con;
  public DBconnection(String resource) {
    this.con=null;
    try {
      Context initContext = new InitialContext();
      Context envContext = (Context)initContext.lookup("java:/comp/env");
      DataSource ds = (DataSource)envContext.lookup(resource);
      this.con = ds.getConnection();                
    catch(SQLException ex) { /* blahblah */ }
    catch(Exception ex) { /* blahblah */ }
    if (this.con==null) { /* blahblah */ }
  /* Update, Query and other methods */
  public void Close() {
    if (this.con!=null) {
      try { this.con.close(); }
      catch(Exception ex) { /* blahblah */ }
}I tried searching Google and this forum, but I couldn't find anything close to this. I greatly appreciate any advice.

Answer 1

Hi, thanks for the reply.
I don't know what the MVC model is, since I am new to JSP and servlets. I do not use servlets as such,
although I believe that the 'snippets' of java code used within the JSP pages are known as Java servlets?
Due to the fact that i only use JSP, this would mean that I can't extend servlets from a controller
servlet. I would be able to implement your idea in Java, but I'm not sure about JSP. Sorry if I am
missing your point, perhaps I misunderstood. Could I have a controller JSP file which accesses the
database using abstract methods, and then passes the results back to the other JSP files??
If you require I can give you more details on my implementation.
Thanks again for the prompt reply,
Craig.