JavaBoutique : Articles : Explore the World of Application Servers

Where Application Servers Fit in 3-tier Architecture

Features of the Application Servers

1.Component Management : - Provides the manager for handling all the components and run time services like session management, synchronous/asynchronous client notifications and executes server business logic.

2.Fault Tolerance: - Ability of the Application server with no single point of failure, defining policies for recovery and fail-over recovery in case of failure of one object or group of objects.

3.Load Balancing: - Ability to send the request to the to different servers depending upon the load and availability of the server.

4.Transaction Management

5.Management Console :- Single point graphical management console for remotely monitoring clients and server clusters

6.Security: Security features for applications security

Types of Application Servers (Source: Upstream Consulting Document)

Application servers are categorised mainly in 3 types:

Web Information Servers: This type of server employs HTML templates and scripts to generate pages incorporating values from the database in them. These types of servers are stateless servers. Some of these types of servers are Netscape Server, HAHT, Allaire, Sybase, SilverStream etc.

Component Servers: The main purpose of these servers are to provide database access and transaction processing services to software components inlcuding DLL's, CORBA, and Java Bean. Firstly, they provide environment for server-side components. Secondly, they provide access to database and other services to the component. These types of servers are stateless servers for instance:
MTS - provides interface for DLL.
and other servers lying in this category are
Sybase Jaguar, IBM Component broker.

Active Application Server: This type of server supports and providesA rich environment for server-side logic expressed as objects, rules and components. These types of servers are stateful servers and best suitable for dealing with based eCommerce and decision processing. Stateful servers are those servers which play the role of transaction co-ordinator and manage the data state, while Stateless servers doesn't do these things completely on their own, but have to rely on database or transaction monitors for the completion of the transaction.

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