[frameworks] 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?

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.

It is just a piece of software or a tool on which your application executes and rapplication capabilities with respect to high availability,scalability,integrating with other softwares or systems without you bothering about your application level code changes .

For example : The operating system on which your application runs requires an I.P change , you do not have to worry about it in your code , it is the middleware stack on which you can simple update the configuration.

Example 2 : You experience problems with your runtime memory allocation and feel that the your application usage has increased , you do not have to much about it unless you have a bug or bottleneck in your code , it is easily achievable by tuning middleware software configuration on which your application runs.

Example 3 : You have multiple disparate software and you need them to talk to each other or send data in a common format which is understandable by all the systems then this is where middleware systems comes handy.

Hope the information provided helps.

Wikipedia has a quite good explanation: http://en.wikipedia.org/wiki/Middleware

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 gives a few examples.

Middleware stands between web applications and web services that natively can't communicate and often are written in different languages/frameworks.

One such example is OWIN middleware for .NET environment, before owin people were forced to host web apps in a microsoft hosting software called IIS. After owin was developed, it has added capacity to host both in IIS and self host, in IIS was just added support for Owin which acted as an interface. Also it become possible to host .NET web apps on Linux via Mono, which again added support for Owin.

It also added capacity to create Single Page Applications, Owin handling Http request/response context, so on top of owin you can add authentication/authorization logic via OAuth2 for example, you can configure middleware to register a class which contains logic of user authentification (for ex. OAuth2 implementation) or class which contains logic of how to manage http request/response messages, that way you can make one application communicate with other applications/services via different data format (like json, xml, etc if you are targeting web).

it is a software layer between the operating system and applications on each side of a distributed computing system in a network. In fact it connects heterogeneous network and software systems.

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

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.

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).

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.

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.

There is a common definition in web application development which is (and I'm making this wording up but it seems to fit): A component which is designed to modify an HTTP request and/or response but does not (usually) serve the response in its entirety, designed to be chained together to form a pipeline of behavioral changes during request processing.

Examples of tasks that are commonly implemented by middleware:

• Gzip response compression
• HTTP authentication
• Request logging

The key point here is that none of these is fully responsible for responding to the client. Instead each changes the behavior in some way as part of the pipeline, leaving the actual response to come from something later in the sequence (pipeline).

Usually, the middlewares are run before some sort of "router", which examines the request (often the path) and calls the appropriate code to generate the response.

Personally, I hate the term "middleware" for its genericity but it is in common use.

Here is an additional explanation specifically applicable to Ruby on Rails.

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.

If I am not wrong, in software application framework, based on the context, you can consider middleware for the following roles that can be combined in order to perform certain activities in between the user request and the application response.

• Adapter
• Sanitizer
• Validator

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

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).