It looks to me like you're bypassing the connection pool and messing
up the way it handles connections. You've only shown a snippet of
code, so I have a couple of questions:
1. After dconn is returned from getConnection, how and when does it get closed?
2. Does the exception happen every time getConnection is called, or
does it maybe succeed on the first call and fail during the second?
When you get a connection from the connection pool, you're supposed to
close it *after* you use it. At
that time the underlying "real" connection is *not* closed, it's just
returned to the pool. That's the point of the connection pool, it
keeps a set of connections open to reduce overhead. Here you're
closing the PoolableConnection immediately, before it's used, which is
wrong.
Here's what I think happens. (This is partly guesswork.)
- DatabaseController.getConnection gets a PoolableConnection, extracts
the underlying real connection (dconn), then returns the
PoolableConnection to the pool.
- The caller of DatabaseController.getConnection uses the real
connection and then closes it.
- Now the pool contains a PoolableConnection whose underlying
connection is closed - This shouldn't happen!
- DatabaseController.getConnection is called a second time, and
returns the same PoolableConnection as before (because it's back in
the pool).
- conn.close() fails this time because the underlying connection was
closed prematurely.
Normally you'd never call getInnermostDelegate, you'd just use the
PoolableConnection returned by DataSource.getConnection and close it
when you're done. Is there a reason that you can't do that?
--
Len
On Feb 18, 2008 11:05 AM, Petter Olofsson <[EMAIL PROTECTED]> wrote:
> Hello tomcat users!
>
> I have a problem using the connection pool in Tomcat. The function
> getConnection() throws the following error message:
>
> [Error message]
> When trying to get a Connection an SQLExcpetion occurred:
> java.sql.SQLException: Already closed.
> at
> org.apache.tomcat.dbcp.dbcp.PoolableConnection.close(PoolableConnection.java:84)
> at
> org.apache.tomcat.dbcp.dbcp.PoolingDataSource$PoolGuardConnectionWrapper.close(PoolingDataSource.java:181)
> at
> org.metria.kiruna.profs.eniro.db.DatabaseController.getConnection(DatabaseController.java:136)
>
> [DatabaseController.java]
> protected Connection getConnection(){
> try{
> Context initContext = new InitialContext();
> Context envContext = (Context)initContext.lookup("java:comp/env");
> DataSource ods = (DataSource) envContext.lookup("jdbc/yyy");
>
> Connection conn = ods.getConnection();
>
> Connection dconn = ((DelegatingConnection)
> conn).getInnermostDelegate();
>
> // if( conn != null && !conn.isClosed() ) // Line 135
> conn.close(); // Line 136
>
> return dconn;
> }catch( SQLException sqle ){
> System.err.println("When trying to get a Connection an
> SQLExcpetion occured.");
> sqle.printStackTrace();
> }catch( NamingException ne ){
> System.err.println("When trying to get a Connection an
> NamingException occured.");
> System.err.println(ne);
> }
> return null;
> }
>
> [Context.xml]
> <Resource accessToUnderlyingConnectionAllowed="true"
> auth="Container"
> driverClassName="oracle.jdbc.OracleDriver"
> maxActive="30"
> maxIdle="10"
> maxWait="1000"
> name="jdbc/yyy"
> username="xxx"
> password="xxx"
> type="javax.sql.DataSource"
> url="jdbc:oracle:thin:@drone:1521:top" />
>
> If the outer connection is left open ( line 135, 136 is deleted) then
> all connections are used until "maxActive" connections are created.
>
> The program uses Tomcat 5.5.26 and Oracle 10.2.3.0.
>
> Does anybody have an idea of why I can't close the outer connection so
> that the connections can be returned to the pool when I am done?
>
> / Petter
>
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