RE: DBCP - Why we close connection
Got the point, thanks a lot guys.
Jawed
-Original Message-
From: Kenneth Huang [mailto:[EMAIL PROTECTED]
Sent: Friday, June 16, 2006 8:08 AM
To: Jakarta Commons Users List
Subject: Re: DBCP - Why we close connection
Hi, Jawed:
I think you just want to know why it close conn in the end.
(1) If you use DB connection pool(DBCP) to visit DB, conn.close() will put
this instance to pool and can be used next time.
(2) If you don't use DBCP in your app, conn.close() will release the
resource used by this instance, esp. a socket connection, or a file
resource.
--
Kenneth Huang
2006-06-16
-
-Original Message-
From：Jawed Nazar Ali
Sent: 2006-06-15 23:00:06
[EMAIL PROTECTED]
Subject：DBCP - Why we close connection
Hello,
try {
conn =
DriverManager.getConnection(jdbc:apache:commons:dbcp:example);
stmt = conn.createStatement();
rset = stmt.executeQuery(args[1]);
int numcols = rset.getMetaData().getColumnCount();
while(rset.next()) {
for(int i=1;i=numcols;i++) {
System.out.print(\t + rset.getString(i));
}
System.out.println();
}
} catch(SQLException e) {
e.printStackTrace();
} finally {
try { rset.close(); } catch(Exception e) { }
try { stmt.close(); } catch(Exception e) { }
try { conn.close(); } catch(Exception e) { }
}
Why we close conn at the end, I don't understand this. Any explanation?
Regards,
Jawed Nazar Ali
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RE: DBCP - Why we close connection
When you get connection with this line
DriverManager.getConnection(jdbc:apache:commons:dbcp:example);
You are actually getting a connection wrapped in dbcp wrapper. When you call
close, the wrapper method close is called instead of close on actual db
driver. This wrapper releases the connection instead of closing it.
Regards,
Tahir
-Original Message-
From: Jawed Nazar Ali [mailto:[EMAIL PROTECTED]
Sent: Thursday, June 15, 2006 8:01 PM
To: commons-user@jakarta.apache.org
Subject: DBCP - Why we close connection
Hello,
try {
conn =
DriverManager.getConnection(jdbc:apache:commons:dbcp:example);
stmt = conn.createStatement();
rset = stmt.executeQuery(args[1]);
int numcols = rset.getMetaData().getColumnCount();
while(rset.next()) {
for(int i=1;i=numcols;i++) {
System.out.print(\t + rset.getString(i));
}
System.out.println();
}
} catch(SQLException e) {
e.printStackTrace();
} finally {
try { rset.close(); } catch(Exception e) { }
try { stmt.close(); } catch(Exception e) { }
try { conn.close(); } catch(Exception e) { }
}
Why we close conn at the end, I don't understand this. Any explanation?
Regards,
Jawed Nazar Ali
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RE: DBCP - Why we close connection
The closing statements at the finally clause assures you the db resources
are released even when an exception is thrown.
This is a good practice, just imagine what will happen using the next code:
try{
conn =
DriverManager.getConnection(jdbc:apache:commons:dbcp:example);
stmt = conn.createStatement();
rset = stmt.executeQuery(args[1]);
int numcols = rset.getMetaData().getColumnCount();
while(rset.next()) {
for(int i=1;i=numcols;i++) {
System.out.print(\t + rset.getString(i));
}
System.out.println();
}
try { rset.close(); } catch(Exception e) { }
try { stmt.close(); } catch(Exception e) { }
try { conn.close(); } catch(Exception e) { }
} catch(SQLException e) {
e.printStackTrace();
}
If an exception occurs in one iteration, you will never release the db
resources (the close statements will never be reached).
I hope it helps you.
Regards,
Alfredo Ledezma Meléndez.
Gerencia Implantación S.A.P.
Supervisor Técnico WEB-ABAP
Radiomóvil DIPSA, S. A. de C. V.
Lago Alberto No. 366, Col. Anáhuac, C.P. 11320
México D.F.
-Original Message-
From: Tahir Akhtar [mailto:[EMAIL PROTECTED]
Sent: Jueves, 15 de Junio de 2006 10:10 a.m.
To: 'Jakarta Commons Users List'; [EMAIL PROTECTED]
Subject: RE: DBCP - Why we close connection
When you get connection with this line
DriverManager.getConnection(jdbc:apache:commons:dbcp:example);
You are actually getting a connection wrapped in dbcp wrapper. When you
call
close, the wrapper method close is called instead of close on actual db
driver. This wrapper releases the connection instead of closing it.
Regards,
Tahir
-Original Message-
From: Jawed Nazar Ali [mailto:[EMAIL PROTECTED]
Sent: Thursday, June 15, 2006 8:01 PM
To: commons-user@jakarta.apache.org
Subject: DBCP - Why we close connection
Hello,
try {
conn =
DriverManager.getConnection(jdbc:apache:commons:dbcp:example);
stmt = conn.createStatement();
rset = stmt.executeQuery(args[1]);
int numcols = rset.getMetaData().getColumnCount();
while(rset.next()) {
for(int i=1;i=numcols;i++) {
System.out.print(\t + rset.getString(i));
}
System.out.println();
}
} catch(SQLException e) {
e.printStackTrace();
} finally {
try { rset.close(); } catch(Exception e) { }
try { stmt.close(); } catch(Exception e) { }
try { conn.close(); } catch(Exception e) { }
}
Why we close conn at the end, I don't understand this. Any explanation?
Regards,
Jawed Nazar Ali
--
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Checked by AVG Free Edition.
Version: 7.1.394 / Virus Database: 268.8.4/364 - Release Date: 6/14/2006
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Checked by AVG Free Edition.
Version: 7.1.394 / Virus Database: 268.8.4/364 - Release Date: 6/14/2006
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Re: DBCP - Why we close connection
Hi, Jawed:
I think you just want to know why it close conn in the end.
(1) If you use DB connection pool(DBCP) to visit DB, conn.close() will put this
instance to pool and can be used next time.
(2) If you don't use DBCP in your app, conn.close() will release the resource
used by this instance, esp. a socket connection, or a file resource.
--
Kenneth Huang
2006-06-16
-
-Original Message-
From：Jawed Nazar Ali
Sent: 2006-06-15 23:00:06
[EMAIL PROTECTED]
Subject：DBCP - Why we close connection
Hello,
try {
conn =
DriverManager.getConnection(jdbc:apache:commons:dbcp:example);
stmt = conn.createStatement();
rset = stmt.executeQuery(args[1]);
int numcols = rset.getMetaData().getColumnCount();
while(rset.next()) {
for(int i=1;i=numcols;i++) {
System.out.print(\t + rset.getString(i));
}
System.out.println();
}
} catch(SQLException e) {
e.printStackTrace();
} finally {
try { rset.close(); } catch(Exception e) { }
try { stmt.close(); } catch(Exception e) { }
try { conn.close(); } catch(Exception e) { }
}
Why we close conn at the end, I don't understand this. Any explanation?
Regards,
Jawed Nazar Ali
