Servlet terminology :
There are some important points that must be
known by the servlet programmer like server, container, get request, post
request etc. Let's first discuss these points before starting the servlet
technology.
The basic terminology used in servlet are given below:
HTTP
HTTP Request Types
Container
Server and Difference between web server and application server
Content Type
Deployment
Difference between Get and Post method
Introduction of XML
HTTP (Hyper Text Transfer Protocol):
Http is the protocol that allows web servers and browsers to exchange data over
the web.
It is a request response protocol.
Http uses reliable TCP connections bydefault on TCP port 80.
It is stateless means each request is considered as the new request. In other
words, server doesn't recognize the user bydefault.
Http Request Methods:
Every request has a header that tells the status of the client. There are many
request methods. Get and Post requests are mostly used.
The http request methods are:
GET
POST
HEAD
PUT
DELETE
OPTIONS
TRACE
HTTP Request Description
GET Asks to get the resource at the requested URL.
POST Asks the server to accept the body info attached. It is like GET
request with extra info sent with the request.
HEAD Asks for only the header part of whatever a GET would return. Just like GET
but with no body.
TRACE Asks for the loopback of the request message, for testing or
troubleshooting.
PUT Says to put the enclosed info (the body) at the requested URL.
DELETE Says to delete the resource at the requested URL.
OPTIONS Asks for a list of the HTTP methods to which the thing at the request
URL can respond
Difference between Get and Post:
There are many differences between the Get and Post request. Let's see these
differences below:
| GET | POST |
| 1) In case of Get request, only limited amount of data can be sent because data is sent in header. | In case of post request, large amount of data can be sent because data is sent in body. |
| 2) Get request is not secured because data is exposed in URL bar. | Post request is secured
because data is not exposed in URL bar. |
| 3) Get request can be bookmarked | Post request cannot be bookmarked |
| 4) Get request is idempotent. It means second request will be ignored until response of first request is delivered. | Post request is
non-idempotent |
| 5) Get request is more efficient and used more than Post | Post request is less efficient and used less than get. |
Container:
It provides runtime environment for JavaEE (j2ee) applications.
It performs many operations that are given below:
Object Pooling
Security etc.
Life Cycle Management
Multithreaded support
Server:
It is a running program or software that provides services.
There are two types of servers:
1)Web Server
2)Application Server
1)Web Server:
Web server contains only web or servlet container. It can be used for
servlet, jsp, struts, jsf etc. It can't be used for EJB.
Example of Web Servers are: Apache Tomcat and Resin.
2)Application Server:
Application server contains Web and EJB containers. It can be used for
servlet, jsp, struts, jsf, ejb etc.
Example of Application Servers are:
JBoss Open-source server from JBoss community.
Glassfish provided by Sun Microsystem. Now acquired by Oracle.
Weblogic provided by Oracle. It more secured.
Websphere provided by IBM.
Content Type
Content Type is also known as MIME (Multipurpose internet Mail Extension) Type.
It is a HTTP header that provides the description about what are you sending to
the browser.
There are many content types:
application/vnd.ms-excel
application/jar
application/pdf
application/octet-stream
application/x-zip
images/jpeg
video/quicktime etc.
text/html
text/plain
application/msword