This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
Firoz, It protects your code from change. If you use a DataSource, your code doesn't need to be aware of the database, password, type of driver, etc. It also allows the driver to be connection pooling and or XA (two phase commit) without changing the code.