Diff. betw. DriverManager and DataSource interface implementation

DriverManager.
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- hampers the application performance as the connections are created/closed in java classes.
- does not support connection pooling.

DataSource
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- improves application performance as connections are not created/closed within a class, they are managed by the application server and can be fetched while at runtime.
- it provides a facility creating a pool of connections
- helpful for enterprise applications