Question: I am publishing everything in the broker database and able to fetch entire component value with the help of ComponentPresentation class and ComponentFactory class. I am using ComponentPresentation.getContent(true) method to fetch the entire content. But my requirement is to retrieve some specific field value from one of the component. but i am unable to do so. Can anybody tell me with an example how I can do that?

Answer: 
In broker final content (xml or html as per your architecture) is published. individual field values (as key values) are not published, so 
You can not directly fetch any component value. you have to parse your Xml/Html to get that field value. 

one of the possible way could be to use metadata, to directly fetch the value from broker.
Somewhere in your solution you need to transform your "naked" content into it's presentation form (usually HTML for web purposes; either directly or via ASP.Net/JSP). With Tridion this is traditionally the responsibility of your page and component templates. 

Recently another approach has gained momentum which is DD4T (Dynamic Delivery For Tridion). With DD4T you publish the content "as is" to the broker and consume the content on the content delivery side in an MVC application; it appears that this is what you are doing (consuming content from the broker in your web application) so you might want to take a look at DD4T.

Alternatively you could write your own solution to push data into the broker and consume it on the other side but that seems like reinventing the wheel...