How connection pooling works in Java and JDBC

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Connection pooling has become the standard for middleware database drivers. The process of creating a connection, always an expensive, time-consuming operation, is multiplied in these environments where a large number of users are accessing the database in short, unconnected operations. Creating connections over and over in these environments is simply too expensive.

The transaction profile for Web applications, probably the most common application in use today, is that of a large number of users performing short, discrete database operations. These applications usually perform work centered around creating a web page that will be sent back to the user's browser. Transactions are generally short-lived, and user sessions are often limited in time.

A connection pool operates by performing the work of creating connections ahead of time, In the case of a JDBC connection pool, a pool of Connection objects is created at the time the application server (or some other server) starts. These objects are then managed by a pool manager that disperses connections as they are requested by clients and returns them to the pool when it determines the client is finished with the Connection object. A great deal of housekeeping is involved in managing these connections.

When the connection pool server starts, it creates a predetermined number of Connection objects. A client application would then perform a JNDI lookup to retrieve a reference to a DataSource object that implements the ConnectionPoolDataSource interface. The client application would not need make any special provisions to use the pooled data source; the code would be no different from code written for a nonpooled DataSource.

When the client application requests a connetion from the ConnetionPoolDataSource, the data source implementation would retrieve a physical connection to the client application. the ConnectionPoolDataSource would return a Connection object that implemented the PooledConnection interface.

The PooledConnection interface dictates the use of event listeners. These event listeners allow the connection pool manager to capture important connection events, such as attempts by the client application to close the connection. When the driver traps a close-connection event, it intercedes and performs a pseudo-close operation that merely takes the Connection object, returns it to the pool of available connection, and performs any housekeeping that is necessary.

The operation of the connection pool should be completely transparent to the client application. The triggering of connection events, the manipulation of the object pool, and the creation and destruction of physical connections are all managed by the pool manager. The activities of the connection pool are, however, configurable by the application developer or the application deployer

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1. View Comment


Could you please include all the relevant files including the Tomcat files to complete this tutorial?


View Tutorial          By: John at 2007-12-19 04:35:54
2. View Comment

i want to know how the connection pooling work with java and jdbc. i want the exact codings how the single connection pool is working and also want how to create the connection pool in java?

View Tutorial          By: V.Selvi at 2010-02-28 21:01:33
3. View Comment

please add code snippets.

View Tutorial          By: jan at 2010-07-27 18:49:53
4. View Comment

Good explanation, Thanks.

View Tutorial          By: bram at 2011-05-06 03:37:54
5. View Comment

super explaination

View Tutorial          By: santhish at 2011-07-06 05:00:54
6. View Comment

it is super

View Tutorial          By: vinod at 2011-09-03 04:06:02
7. View Comment

Very good explanation but i need to know how the connection pooing is configure in various servers pls provide the info


View Tutorial          By: surender at 2011-11-17 11:15:22
8. View Comment

plz send me 1 ex that will explain how to use connection pooling using MySQl

View Tutorial          By: abhijit marne at 2011-12-09 06:32:07
9. View Comment

If the database server goes down, should the connection pool be refreshed. If conection pool is not refreshed, can the client use the existing connection object and try to connect successfully. Will this result in winsoc error.

View Tutorial          By: Naveen Gowd at 2012-02-02 07:17:38
10. View Comment

Assume scenario:
- i have set connection pool size as 5 in my application.
- when 5 users access my app all 5 connections will be utilized from the pool.

What if user 6 access the app & still all 5 users are currently using the app.
My understanding is 1 connection will be used by 1 thread/user. Correct me if i'm wrong.


View Tutorial          By: Dan at 2012-02-22 09:48:46
11. View Comment

good explanation .... Thanks

View Tutorial          By: nazeer at 2012-05-24 09:18:19
12. View Comment

if suppose i am having connection pool max size 30 and 30 connections are active for 1 hr then, what will happen with other connections(excluing active first 30th connections) which are waiting....will they wait for 1 hr? And one more question is what will happen if we not give max connection size?

View Tutorial          By: Shrikant at 2012-07-20 12:09:33
13. View Comment

Please add the code snippet ..

View Tutorial          By: mari selvam at 2012-08-23 10:13:51
14. View Comment

1. Performance

Object pooling provides better application performance As object creation is not done when client actually need it to perform some operation on it Instead objects are already created in the pool and readily available to perform any time. So Object creation activity is done much before So it does help in achieving better run-time performance

2. Object sharing :

Object Pooling encourage the concept of sharing. Objects available in pool can be shared among multiple worker threads . One thread Use the Object and once used it returns back to its Object pool and then it can be used by some other worker thread. So once created objects are not destroyed and thus destruction and creation again and again is not required. That again help in generating better performing code.

3. Control on Object instances :
By declaring size of Object pool we can control the no of instance creation. Thus a finite no of objects are created as decided depending upon required application capacity and scalability or peak load.

4. Memory conservation :
Finite no of instances are created So it helps in better memory management . Too many instances are not

Read through extensive details here :

View Tutorial          By: sonia at 2013-09-21 20:22:49

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