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Opening the Closed Connection

Naresh Shanmugam
Ranch Hand

Joined: Jul 16, 2010
Posts: 84
Is it possible to re-open the closed connection?. If no how does the datasource concept work? Does it create a new connection object when ever we close the connection?
Scott Selikoff
Saloon Keeper

Joined: Oct 23, 2005
Posts: 3697
    
    5

No, you cannot reopen a closed connection. It's a dead object for the most part and one that represents a physically dead connection.

Data sources create a new connection on getConnection(), as described in the API. Database pools on the other hand maintain a set of connections and open/close them as needed. If the number of available connections is below the pool minimum, a new one is opened.

The key thing to note is that once you open a connection with a DataSource, it is your responsibility to make sure it gets closed, which is why you should always use a finally block for closing JDBC resources.


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Naresh Shanmugam
Ranch Hand

Joined: Jul 16, 2010
Posts: 84
If the number of available connections is below the pool minimum, a new one is opened.


Scott, Does this mean a new connection object will be created every time the available connections is below the minimum limit or when the existing connection is closed?
Scott Selikoff
Saloon Keeper

Joined: Oct 23, 2005
Posts: 3697
    
    5

Database pooling is complex and is generally vendor-specific. That said, most have a minimum and maximum number of connections and will auto-create connections if the number available falls below the minimum.
Naresh Shanmugam
Ranch Hand

Joined: Jul 16, 2010
Posts: 84
will auto-create connections if the number available falls below the minimum
If that is the case what advantage do i get from connection pooling Scott, i could create connection object when ever it is required in my code? What is the advantage of having predefined number of connections in the connection pooling?
 
It is sorta covered in the JavaRanch Style Guide.
 
subject: Opening the Closed Connection
 
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