1. Designing software applications
Lection 4
Middleware software

2. Dependency Injection
Process of an external dependency resolving for a class
Design pattern

3. Dependency injection

4. Software components
Front-end
Back-end
Middleware

5. Middleware
Middleware is a computer software that provides services to software applications beyond those available from the operating system.
Software glue

6. Middleware
Application server
Message bus

7. Middleware transactions, threading, messaging.
Data format and transformation

8. Middleware
Constant change: The very nature of EAI is dynamic and requires dynamic project managers to manage their implementation.
Shortage of EAI experts: EAI requires knowledge of many issues and technical aspects.
Competing standards: Within the EAI field, the paradox is that EAI standards themselves are not universal.
EAI is a tool paradigm: EAI is not a tool, but rather a system and should be implemented as such.
Building interfaces is an art: Engineering the solution is not sufficient. Solutions need to be negotiated with user departments to reach a common consensus on the final outcome. A lack of consensus on interface designs leads to excessive effort to map between various systems data requirements.
Loss of detail: Information that seemed unimportant at an earlier stage may become crucial later.
Accountability: Since so many departments have many conflicting requirements, there should be clear accountability for the system's final structure.

9. Requirements to middleware implementation
Standard based

10. Software intergration

11. Software intergration

12. Software intergration

13. Software intergration
How to get reference to component?
How to create and dispose objects?
Can the component services be used exclusively or by multiple clients?

14. Component Object Model (COM)
Standard for interprocess communication
Binary format
Interface based

15. Web-services
Method of communication
Tool for application integration

16. Web-service
Stateless
No identity
Interface based

17. Web services
SOAP web-services
REST web-services