What are the major differences between Web Server and
Application Server?

Answer Posted / ravi v v

Here you go:

-------------------
The Web server:
-------------------
A Web server handles the HTTP protocol. When the Web server
receives an HTTP request, it responds with an HTTP
response, such as sending back an HTML page. To process a
request, a Web server may respond with a static HTML page
or image, send a redirect, or delegate the dynamic response
generation to some other program such as CGI scripts, JSPs
(JavaServer Pages), servlets, ASPs (Active Server Pages),
server-side JavaScripts, or some other server-side
technology. Whatever their purpose, such server-side
programs generate a response, most often in HTML, for
viewing in a Web browser.

Understand that a Web server's delegation model is fairly
simple. When a request comes into the Web server, the Web
server simply passes the request to the program best able
to handle it. The Web server doesn't provide any
functionality beyond simply providing an environment in
which the server-side program can execute and pass back the
generated responses. The server-side program usually
provides for itself such functions as transaction
processing, database connectivity, and messaging.

While a Web server may not itself support transactions or
database connection pooling, it may employ various
strategies for fault tolerance and scalability such as load
balancing, caching, and clustering—features oftentimes
erroneously assigned as features reserved only for
application servers.
----------------------------
The application server:
----------------------------
As for the application server, according to our definition,
an application server exposes business logic to client
applications through various protocols, possibly including
HTTP. While a Web server mainly deals with sending HTML for
display in a Web browser, an application server provides
access to business logic for use by client application
programs. The application program can use this logic just
as it would call a method on an object (or a function in
the procedural world).

Such application server clients can include GUIs (graphical
user interface) running on a PC, a Web server, or even
other application servers. The information traveling back
and forth between an application server and its client is
not restricted to simple display markup. Instead, the
information is program logic. Since the logic takes the
form of data and method calls and not static HTML, the
client can employ the exposed business logic however it
wants.

In most cases, the server exposes this business logic
through a component API, such as the EJB (Enterprise
JavaBean) component model found on J2EE (Java 2 Platform,
Enterprise Edition) application servers. Moreover, the
application server manages its own resources. Such gate-
keeping duties include security, transaction processing,
resource pooling, and messaging. Like a Web server, an
application server may also employ various scalability and
fault-tolerance techniques.

Cheers
Ravi V V
Capita

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