View source for Java EE Modular Solutions

Web tier access EIS direct or though EJB
= use of tiers =

==  Decide on requirements ==
Based on:
* functionality
* complexity
* scalability

== EJB tier ==
* security
* transactions
* distributed processing

== Web tier use of JDBC implications ==
* ideal for small simple applications with few transaction requirements

* implements all core functionality
* implements transaction management - JTA
Implies:
* poor scaling with complexity
* monolithic

== Using Web and EJB tier ==
* better for:
** building large scale complex applications
** complex security/transaction requirements
** performance requirements
* implications
** Splits business logic into EJB tier
** web tier becomes mainly request processing and view

= Use of distribution =
Must be designed for distributed architecture 
Use of:
* service locator - to hide location/naming resolution
* business delegate - to hide remote nature
* composite entity/transfer object assembler - to reduce fine grained access

== Local == 
* same virtual machine
* no network overhead
* no serialisation overhead
* low latency
* allows for fine grained control/access

== Remote ==
* more modular
* more reusable
* lower dependency between components
* higher overheads - data copying, latency
* security considerations
* typically more scalable (horizontally) - can split and run on more machines
* more highly available - easier to migrate to different machine in the event of failures