doGet is called in response to an HTTP GET request. This 
happens when users click on a link, or enter a URL into the 
browser's address bar. It also happens with some HTML FORMs 
(those with METHOD="GET" specified in the FORM tag). 
doPost is called in response to an HTTP POST request. This 
happens with some HTML FORMs (those with METHOD="POST" 
specified in the FORM tag). 

Both methods are called by the default (superclass) 
implementation of service in the HttpServlet base class. 
You should override one or both to perform your servlet's 
actions. You probably shouldn't override service().

doGet method will append data to URL while transferring 
data to the server.

doPost method will not append data. It is considered to be 
secured. The data will be inside the body of request and 
response.

doget is actually used as something dats used to retrieve data and dopost is something dats used to insert data...and dopost is more confidential about data...

The doGet  we can send limited data’s only 0 to 255 
characters but doGet we can pass unlimited datas

Both are processing for request and response of a client.By
using doGet we can send less amount of data compare to doPost.
If we use doget the users sensitive data(user name &
password)will be displayed in the URL.

doGet(): 1.The query String "display" the Client browser.
         2.The max of query string 0 to 255 Character to 
           be send.  

doPost(): 1. The query String to "Hide" the Client browser.
          2. No limitation of data to be send.
          3. The data to be send separate packet on the 
             server.

doGet will append the request parameters as a query string
to the url,
where as the doPost will post the data content on the body
of the jsp page

doGet:-
1)doGet() method this is default HttpRequest method
2)The request parameters as a query string in the Visible in
address bar.
3)it sends limited data
4)security is low because query string visible in the
address bar
5)It doesn't used multiform content data(i.e file uploading
operation) never used.
6)small scale application.

doPost:-

1)doPost()method this n't a default HttpRequest method
2)The request parameters as a query string does n't  Visible
in address bar.
3)it sends unlimited data.
4)Security is high.
5)its used for multiform content data
6)large scale application.