How to use JDBC Connection Pools in a standalone application?

Hi, there,
I have a question about how to use JDBC Connection Pools in an application. I know well about connection pool itself, but I am not quite sure how to keep the pool management object alive all the time to avoid being destroyed by garbage collection.
for example, at the website: http://www.developer.com/java/other/article.php/626291, there is a simple connection pool implementation. there are three classes:JDBCConnection, the application's gateway to the database; JDBCConnectionImpl, the real class/object to provide connection; and JDBCPool, the management class to manage connection pool composed by JDBCConnectionImpl. JDBCPool is designed by Singleton pattern to make sure only one instance. supposing there is only one client to use connection for many times, I guess it's ok because this client first needs instantiate JDBCPool and JDBCConnectionImpl and then will hold the reference to JDBCPool all the time. but how about many clients want to use this JDBCPool? supposing client1 finishes using JDBCPool and quits, then JDBCPool will be destroyed by garbage collection since there is no reference to it, also all the connections of JDBCConnectionImpl in this pool will be destroyed too. that means the next client needs recreate pool and connections! so my question is that if there is a way to keep pool management instance alive all the time to provide connection to any client at any time. I guess maybe I can set the pool management class as daemon thread to solve this problem, but I am not quite sure. besides, there is some other problems about daemon thread, for example, how to make sure there is only one daemon instance? how to quit it gracefully? because once the whole application quits, the daemon thread also quits by force. in that case, all the connections in the pool won't get chance to close.
I know there is another solution by JNDI if we develop servlet application. Tomcat provides an easy way to setup JNDI database pooling source that is available to JSP and Servlet. but how about a standalone application? I mean there is no JNDI service provider. it seems a good solution to combine Commons DBCP with JNID or Apache's Naming (http://jakarta.apache.org/commons/dbcp/index.html). but still, I don't know how to keep pool management instance alive all the time. once we create a JNDI enviroment or naming, if it will save in the memory automatically all the time? or we must implement it as a daemon thread?
any hint will be great apprieciated!
Sam

To my knoledge the pool management instance stays alive as long as the pool is alive. What you have to figure out is how to keep a reference to it if you need to later access it.

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************************************servlet example**********************************
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public static Connection getConnection(String lookup) throws NamingException, SQLException {
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package CraigsClasses;
import javax.servlet.*;
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Zhenhao Qi wrote:
thanks! Joe.
The SQL statement itself can no longer be simplified, the long excuation time is due to the database size and complicated Select criteria. I can easily reproduce the problem by using this SQL. I tried "BEA's Oracle driver (Type 4): Version 8.1.7,9.0.1,9.2.0". the question can be dissect into 2 pieces:
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Are you doing weblogic-controlled transactions? Are you/can you
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If you can duplicate the problem using the weblogic.jdbc.oracle.OracleDriver
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want to use the thin driver, because we will do the same JDBC calls to
either driver, and the debug would prove (if) we set up a query timeout
and if we call cancel(). If we do, then we can know that it is the Oracle
driver failing in these regards.
Joe

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Dave Snaith wrote:
This morning weblogic 8.1.5 complained it couldn't expand a connection pool because it had reached is max concurrent connects limit.
The issue I have is that I don't actually know what is using the connection pool. It should be defunct and redundent but obviously not.
This caused all the threads to be consumed and the managed server hung.
Does anyone know wether it's possible to interigate the pool to find out what it's doing ? I can't check the db as it's managed by another company and I have a v limited read only account.... I can't even select from v&session.
Cheers in advance for any help.If the pool is not supposed to be used, disable it via the console,
and whatever applications are still trying to use it will get
quick exceptions.
Joe

Weblogic 7.0 , MySQL 3.23 JDBC Connection Pools

i am using weblogic 7.0 and MySQL 3.23 and right now my objective is to create,
configure and test a JDBC
connection pool using the Administrative console.
Here is what i have done till now
- set the classpath of the MySQL driver in the startWLS.cmd like this
SET MYSQL_DRIVER=C:\mysqldriver\mysql-connector-java-2.0.14\mysql-connector-java-2.0.14-bin.jar
set CLASSPATH=%MYSQL_DRIVER%;%CLASSPATH%
- using the weblogic administrative console i have created a new connection pool
named as
testpool.
- Here is what i have in the testpool general tab
Name: testpool
URL: jdbc:mysql//localhost:3306/test (test is the name of the database in mysql)
Driver Classname: org.gjt.mm.mysql.Driver
I have not entered any Properties, ACL Name, Password or Open String Password.
- Now i go the the Testing tab and enter a name of a table in my test database
and click on Apply
and on the command window i am getting the following exception
java.sql.SQLException No suitable driver
Thanks in advance,
Ashish

Thanks a lot Slava. After reading your mail and the post i was able to get it working.
"Slava Imeshev" <[email protected]> wrote:
Hi Ashish,
I figured out what's the problem. URL in the connection pool
definition is malformed. It's
jdbc:mysql//localhost:3306/test
while the correct one should have colon after mysql:
jdbc:mysql://localhost:3306/test
Regards,
Slava Imeshev
"Ashish Sureka" <[email protected]> wrote in message
news:[email protected]...
I am sorry, the program that i posted here is not comming properlyformatted but
i am able to run a simple java program that connects to MySQL and alsoa
servlet
that connects to the MySQL. The only problem i am having is includingthe
MySQL
driver jar files to the weblogic server classpath.
Thanks,
Ashish.
"Ashish Sureka" <[email protected]> wrote:
Hello Joseph Weinstein,
Actually, i already tried the same approach that you have mentioned
in
your reply
before i posted my message here. Following is the program that i use
to check
MySQL connection.
import java.sql.*;
public class MySQLConnect
public static void main(String[] args) throws Exception
try {
Class.forName ( "org.gjt.mm.mysql.Driver" );
System.out.println ( "MySQL Driver Found" );
} catch ( java.lang.ClassNotFoundException e ) {
System.out.println("MySQL JDBC Driver not found ... ");
throw ( e );
String url = "";
Connection con = null;
try {
url = "jdbc:mysql://" + "localhost:3306" + "/" + "test";
con = DriverManager.getConnection(url);
System.out.println("Connection established to " + url + "");
} catch ( java.sql.SQLException e ) {
System.out.println("Connection couldn't be established to " + url);
String sqlStatement = "SELECT * FROM testtable";
try {
Statement s = con.createStatement();
s.execute (sqlStatement);
s.close ( );
} catch ( SQLException e ) {
System.out.println ( "Error executing sql statement" );
con.close();
The classpath that i use to run this program is
SET PATH=C:\bea\jdk131_03\bin
SETCLASSPATH=C:\bea\jdk131_03\jre\lib\rt.jar;C:\bea\weblogic700\ebcc\lib\ext\se
rvlet.jar;C:\CSC413\Demos\HelloApp\HelloAppJAR
SET CLASSPATH=%CLASSPATH%;C:\bea\weblogic700\server\lib\weblogic.jar
SETMYSQL_DRIVER=C:\mysqldriver\mysql-connector-java-2.0.14\mysql-connector-java
-2.0.14-bin.jar
set CLASSPATH=.;%MYSQL_DRIVER%;%CLASSPATH%
I have also written a Servlet which checks the MySQL connection. For
the servlet
i added the MySQL driver jar files in the WEB-INF/lib directory ofthe
servlet
web application and it is working fine.
do you want me to attach the startWLS.cmd file that i changed to include
the MySQL
driver classpath.
Thanks for your replies,
Ashish.
Joseph Weinstein <[email protected]> wrote:
Ashish Sureka wrote:
When i start the weblogic server using the command prompt by executingthe startWLS.cmd,
i can see the classpath the server is using on the command window
and
that includes
the jar file for the MySQL driver but still it is throwing a
SQLException
and
saying that No Suitable driver.
How do i include a external library or jar file on the weblogic
server's
classpath.
is there a specific directory where i should put the MySQL driver
jar
file .
Thanks,
Ashish.No. Let's simplfy the problem. Please run a tiny standalone Java
program
that
just makes a JDBC connection to your MySQL DBMS, with no weblogic
code in the picture. When you succeed at this, show me the CLASSPATH
and
PATH of the shell that ran the program successfully, and show methe
few lines
of code that made the connection. Then we will know the problem.It
may
be that
the URL you're passing to the pool is not exactly correct for that
driver.
Joe
Joseph Weinstein <[email protected]> wrote:
Ashish Sureka wrote:
i am using weblogic 7.0 and MySQL 3.23 and right now my objective
is
to create,
configure and test a JDBC
connection pool using the Administrative console.
Here is what i have done till now
- set the classpath of the MySQL driver in the startWLS.cmd
like
this
SET
MYSQL_DRIVER=C:\mysqldriver\mysql-connector-java-2.0.14\mysql-connector-java
-2.0.14-bin.jar
set CLASSPATH=%MYSQL_DRIVER%;%CLASSPATH%
- using the weblogic administrative console i have created anew
connection
pool
named as
testpool.
- Here is what i have in the testpool general tab
Name: testpool
URL: jdbc:mysql//localhost:3306/test (test is the name of
the
database
in mysql)
Driver Classname: org.gjt.mm.mysql.Driver
I have not entered any Properties, ACL Name, Password or
Open
String
Password.
- Now i go the the Testing tab and enter a name of a table in
my
test
database
and click on Apply
and on the command window i am getting the following exception
java.sql.SQLException No suitable driverWatch the first lines that the server prints out when the script
starts
it. The script
shows the classpath that was constructed for the server. It is
likely
that you need
to do something else to ensure your driver is really in the classpath
the server uses.
Joe
Thanks in advance,
Ashish

How to test if connection pool is set up correctly in WL 7 SP 7

Hi all,
2 questions.
1) how do i test if the connection pool i set is working? in the testing tab of the jdbc connection pool in the console page, there is a Test Table Name, i entered 'dual' in the text field. After i clicked apply, there is no indication if i set it up correctly.
2)After i configure the connection pool, do i need to configure the data sources?

Could you please try using a "Test_When" statement?
Karthik

Load balancing to JDBC connection pool

from http://e-docs.bea.com/wls/docs61///////cluster/overview.html
"WebLogic Server provides limited load balancing support for managing JDBC
connections in a cluster. If you create an identical JDBC DataSource in each
clustered WebLogic Server instance and configure those DataSources to use
different connection pools, the cluster can support load balancing for JDBC
connections. Note, however, that WebLogic Server provides no special load
balancing policies for accessing connection pools. If one of your connection
pools runs out of JDBC connections, the load balancing algorithm may still
direct connection requests to the empty pool."
How is this different from creating one connection pool with one datasource
and targetting the cluster. Are they talking about load-balancing to
different databases, or different servers in WLS. from a servlet or from a
client side app?
Can anyone elaborate?
Thanks in advance.

hi,
without knowing the entire set of requirements or the motivation behind doing this, a few words from me
this is usually done transparently to the applications server, that is having eg. Oracle instances mirroring eachother for extreme high-availability requirements.
1. I would have taken the liberty of calling this business funcionality and let my middleware do the implementation of this. The most elegant solution would probably be to call the master DB for the CUD operation, then post a message to a queue letting the slave DB be updated asynchronously. If the message could not be sent, throw an exception and have the entire operation rolled back.
If however this must happen realtime and transactions must be consistent, there are a few points to consider. And the quieing bit would not work.
if this is something that should be done for all Create, Update and Delete operations, an intercepting JDBC driver could do the trick. Although there are all sorts of different problems that could arise from this, for starters, at least one of the DBMS involved here should be XA compliant. If the entire transaction should be XA compliant, both DBMS must be XA compliant. Next as for the transaction towards the "mirroring" DBMS you would have to do all the transaction stuff your self.
For an example of an intercepting JDBC driver, I found thisone
http://media.datadirect.com/download/docs/jdbc/jdbcref/spy.html
I would guess that there are quite a few more.
- [url http://blog.thej2eestruggle.com]Anders Mathisen
Edited by anders.mathisen at 01/21/2007 2:53 PM

How to use JDBC Connection Pools in a standalone application?

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