What is middleware exactly?

I have heard a lot of people talking recently about _middleware_, but what is the exact definition of middleware? When I look into middleware, I find a lot of information and some definitions, but while reading these information and definitions, it seems that mostly all 'wares' are in the middle of something. So, are all things middleware?

Or do you have an example of a ware that isn't middleware?

Some examples of middleware: CORBA, Remote Method Invocation (RMI),...

The examples mentioned above are all pieces of software allowing you to take care of communication between different processes (either running on the same machine or distributed over e.g. the internet).

Wikipedia has a quite good explanation:

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It starts with

> Middleware is computer software that connects software components or applications. The software consists of a set of services that allows multiple processes running on one or more machines to interact.

[What is Middleware](

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) gives a few examples.

There are (at least) three different definitions I'm aware of

- in business computing, middleware is messaging and integration software between applications and services

- in gaming, middleware is pretty well anything that is provided by a third-party

- in (some) embedded software systems, middleware provides services that applications use, which are composed out of the functions provided by the hardware abstraction layer - it sits between the application layer and the hardware abstraction layer.

Middleware is a terribly nebulous term. What is "middleware" in one case won't be in another. In general, you can expect something classed as middleware to have the following characteristics:

* Primarily (usually exclusively) software; usually doesn't need any specialized hardware.

* If it _weren't_ there, applications that depend on it would have to incorporate it as part of their application and would experience a lot of duplication.

* Almost certainly connects two applications and passes data between them.

You'll notice that this is pretty much the same definition as an operating system. So, for instance, a TCP/IP stack or caching could be considered middleware. But your OS could provide the same features, too. Indeed, middleware can be thought of like a special extension to an operating system, specific to a set of applications that depend on it. It just provides a higher-level service.

Some examples of middleware:

* distributed cache
* message queue
* transaction monitor
* packet rewriter
* automated backup system

Middleware is a general term for software that serves to "glue together" separate, often complex and already existing, programs. Some software components that are frequently connected with middleware include enterprise applications and Web services.

**Middleware** is about how our application responds to incoming requests. Middlewares look into the incoming request, and make decisions based on this request. We can build entire applications only using middlewares. For e.g. ASP.NET is a web framework comprising of following chief HTTP middleware components.

1. Exception/error handling
2. Static file server
3. Authentication
4. MVC
[![Middlewares][1]][1]


[1]:

As shown in the above diagram, there are various middleware components in ASP.NET which receive the incoming request, and redirect it to a C# class (in this case a controller class).

I always thought of it as the oldest software I have had to install. The total app used a web server, a database server, and an application server. The web server being the middleware between the data and the app.

From my own experience with webwork, a middleware was stuff between users (the web browser) and the backend database. It was the software that took stuff that users put in (example: orders for iPads, did some magical business logic, i.e. check if there are enough iPads available to fill the order) and updated the backend database to reflect those changes.

Simply put Middleware is a software component which provides services to integrate disparate systems together.

In an complex enterprise environment, there are a number of challenges when you need to integrate two or more enterprise systems together to talk to each other. Normally these systems do not understand each others language as they are developed on different platforms using different languages (like C++, Java, Cobol, etc.).

So here comes middleware software in picture which provides services like

- transformation of messages formats from one app to other,
- routing and enriching messages besides taking care of security,
- encryption,
- validation and
- applying different business rules to these messages.

A typical example of middleware is an _ESB_ products like IBM message broker (WMB/IIB), WESB, Datapower XI50, Oracle Fusion, Mule and many others.

Therefore, middleware sits mostly in between the service consuming apps and services provider apps and help these apps to talk to each other.