84 Seven doXxx(-,-) Methods of HttpServlet | Adv Java Servlet programming Tutorial

#Seven doXxx(-,-) #Methods of #HttpServlet: #Advance #Java #Servlet #Programming #Tutorial
There are seven doXxx(-,-) methods that client can use to send request to web apps deployed in servers.

To process these request in our servlet program, we can use doXxx(-,-) methods:

HTTP Request Methods are:
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GET
POST
HEAD
PUT
DELETE
OPTIONS
TRACE

doXxx(-,-) of Servlet API are:
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doGet(HttpServletRequest, HttpServletReponse)- To process GET method based request
doPost(-,-) To process POST method based request
doHead(-,-) To process HEAD method based request
doPut(-,-) To process PUT method based request
doDelete(-,-) To process DELETE method based request
doOptions(-,-) To process OPTIONS method based request
doTrace(-,-) To process TRACE method based request

- Eventhough there are 7 doXxx(-,-) methods, we use only doGet(-,-), doPost(-,-) in our servlet Program, because clients form pages can generate only "GET", "POST" method based HTTP request.

HTTP Request Methods:
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1) GET: This is designed to send request to server and to gather limited data from server. But this request can carry limited amount of data (max of 256KB). This request related response contains all the details (Misc information, response header, response body)

2) POST: Designed to send unlimited amount of data along with request to server. Suitable for file uploading operations. This request related response contains all the details.

3) HEAD: same as 'GET' method but this request related response contains only response headers. This method is useful to check whether web resource program is available or Not.

4) PUT: This method is useful for FTP application to make FTP application to place a file or web resource program on to the already hosted web application of web server from client machine.

5) DELETE: Its useful for FTP application to delete existing file or web resource program of already/existing hosted web appliction in the web server.

6) OPTIONS: This OPTIONS based request determies which HTTP request methods that the server supports to give request to web resource.

7) TRACE: if request given to web resource program, fails to generate program then give next request to that web resource program having TRACE method then server gives the complete flow related to request-arrival to response generation. Based on this we can debug the problems.

Eg: if we give "OPTIONS" methods based request to a servlet program that contain doGet(-,-) method then the generated response contains

allow: GET, HEAD, TRACE, OPTIONS.

indicates can give request to servlet program using these request.