What is Middleware?
Middleware is software that lies between an operating system and the applications running on it. Essentially functioning as a hidden translation layer, middleware enables communication and data management for distributed applications. It’s sometimes called plumbing, as it connects two applications together so data and databases can be easily passed between the “pipe.” Using middleware allows users to perform such requests as submitting forms on a web browser, or allowing the webserver to return dynamic web pages based on a user’s profile.
Components of Middleware Architecture
Middleware solutions are usually software-only, with hardware components very rarely in the mix. The idea of middleware is to provide a virtual layer between various applications and the platform layer.
Most middleware follows the service-oriented architecture (SOA) design or is designed as a platform-as-a-service (PaaS) solution. SOA is an architectural style that tries to achieve loosely coupled software applications that interact among themselves to run as a whole. It is adopted by organizations trying to decouple all their business units, depending on integration and reusability for daily operations. SOA allows organizations to use existing applications and system investments.
Every requirement of middleware points toward service-oriented architecture. This calls for individual, reusable components with their own topology. Each of these components must be able to interact with one another and other parts of the system. Apart from some basic components, each type of middleware needs a specific component. For example, a database middleware needs a database manager component.
Here are the key entities of each generic middleware component that is deployed across the system:
- Middleware management console: A middleware management console is a single pane of glass that captures a bird’s eye view of the middleware architecture. This is especially important with enterprise application middleware, designed and implemented specifically with an organization’s business requirements in mind. This console provides an overview of events and activities, transactions, configuration management, and contract rules.
- Client interface (or application interface): This is the interface that the middleware exposes to the client or application services. It allows applications to use predefined constructs to initiate a transaction involving the database, platform, or other backend servers. This component simplifies application development and deployment, one of the biggest benefits of using any middleware solution.
- Middleware internal interface: This is the interface through which middleware instances communicate with each other to maintain the overall middleware structure. This component is required because various middleware instances must work together internally to appear as a single continuous layer. This is usually done using a special protocol defined by the middleware, which doesn’t overlap with other communication protocols.
- Platform interface: Middleware needs to work across multiple platforms, irrespective of where it resides. This is the interface that is in direct contact with the backend servers. Every time a new platform is introduced, say by the cloud provider, this interface needs to be updated to support it. All other components of the middleware remain relatively unchanged.
- Contract manager: A contract manager is the enforcer of various rules imposed by each application, data control, and server. All lines of communication and event initiation must follow these contracts to ensure transparency and minimize breakage. The contract manager makes sure business logic remains intact and is valid. All contract breaches are thrown back to the application, ensuring that the entire system does not go down because of them.
- Session manager: The session manager ensures that all communication and transaction requests are valid and have not timed out. It establishes the connections, to begin with, allowing requests to flow back and forth. It also manages the session history for audit purposes. A session manager is one way of ensuring that the middleware is secure.
- Database manager (if required): The database manager controls connections to the database, changing addition, modification, and deletion of data based on the DB service used. Since this vastly varies on the type of database used (file-based or table-based), where it resides (internal data center or cloud), and how sensitive the data is, security is an important consideration for this component.
- Runtime monitor: The runtime monitor keeps an eye on all contract validations, session history, requests, and responses. It is used by IT admin and security teams to detect and flag any anomalous activity. It also usually provides the base for reporting engines that churn out audit reports for compliance purposes.
Besides these, each type of middleware may require unique services to fulfill its requirements. A device middleware concentrates on the particular device it caters to. Each of these components is designed and built with a varying focus based on the type. Message-oriented middleware needs a robust common messaging framework, while the database manager is not required to function.
Types of Middleware
There are many different types of middleware. Some focus on specific types of connectivity, others on specific applications, application components, and devices; some combine middleware capabilities for a specific development task. Some of the best-known and most commonly used types of middleware software include:
- Message-oriented middleware (MOM) enables application components to use different messaging protocols to communicate to exchange messages. In addition to translating - or transforming - messages between applications, MOM manages the routing of the messages so they always get to the proper components in the proper order. Examples of MOM include message queues and message brokers.
- Remote procedure call (RPC) middleware enables one application to trigger a procedure in another application - running on the same computer or on a different computer or network - as if both were part of the same application on the same computer.
- Data or database middleware simplifies access to, and interaction with, back-end databases. Typically database middleware is some form of SQL database server.
- API (application programming interface) middleware provides tools developers can use to create, expose and manage APIs for their applications - so that other developers can connect to them. Some API middleware includes tools for monetizing APIs - enabling other organizations to use them, at cost. Examples of API middleware include API management platforms, API gateways, and API developer portals.
- Object request broker (ORB) middleware acts as a broker between a request from one application object or component, and the fulfillment of that request by another object or component on the distributed network. ORBs operate with the Common Object Request Broker Architecture (CORBA), which enables one software component to make a request of another without knowing where the other is hosted, or what its UI looks like - the "brokering" handles this information during the exchange.
- Transactional middleware provides services to support the execution of data transactions across a distributed network. The best-known transactional middleware is transaction processing monitors (TPMs), which ensure that transactions proceed from one step to the next - executing the data exchange, adding/changing/deleting data where needed, etc. - through to completion.
- Asynchronous data streaming middleware replicates a data stream in an intermediate store, enabling data sharing between multiple applications. Apache Kafka is one of the best-known examples of middleware for real-time data streaming.
- Device middleware provides a focused set of integration and connectivity capabilities for developing apps for a specific mobile OS.
- Portal middleware provides tools and resources for integrating content and capabilities from various related applications 'at the glass' - or on a single screen - to create a single, composite application.
- Robotics middleware simplifies the process of integrating robotic hardware, firmware, and software from multiple manufacturers and locations.
Usage of Middleware
Many definitions exist regarding the categorization of middleware specifying either the field that it is used or the application module it serves. In recent bibliography, the main categories of middleware are the following:
- Transactional: Processing of multiple synchronous/ asynchronous transactions, serving as a cluster of associated requests from distributed systems such as bank transactions or credit card payments.
- Message-oriented: Message queue and message passing architectures, which support synchronous/asynchronous communication.
- Procedural: Remote and local architectures to connect, pass, and retrieve software responses of asynchronous systems communications such as a call operation.
- Object-oriented: Similar to procedural middleware, however, this type of middleware incorporates object-oriented programming design principles. Analytically, its software component encompasses object references, exceptions, and inheritance of properties via distributed object requests.
Applications of Middleware
There are specifically two applications of middleware: enterprise and platform.
- Enterprise middleware: Enterprise middleware connects software components or enterprise applications. It is the layer of software between the operating system and the applications on either side of a computer network, usually supporting complex, distributed business software applications.
- Platform middleware: Platform middleware connects different application architectures. Some technology firms operate using multiple application structures. When firms merge or when there are third-party application acquisitions, a company may find that they are using multiple structures. Middleware supports these structures and provides methods in three arenas of interconnection: development environments, production, and testing. In all of these arenas, middleware transfers data from application to application, as well as between databases and files.
How Middleware Works
Middleware abstracts the underlying communication process between components. This means that the frontend application communicates only to the middleware and does not have to learn the language of other backend software components.
- Messaging framework: A messaging framework facilitates the exchange of data between frontend and backend applications. Common frameworks include the following:
- Representational State Transfer (REST API)
- Extensible Markup Language (XML)
- Web services
- Simple Object Access Protocol (SOAP)
The messaging frameworks provide a common communication interface for applications in different operating platforms and languages. Applications write and read data in a standardized format provided by the messaging framework.
- Example of middleware: For example, a web server is a middleware that connects websites to the backend database. When you submit a form on a website, your computer sends the request in XML or JSON to the web server. Then, the web server runs the business logic based on the request, retrieves information from databases, or communicates to other microservices using different protocols.
- Other middleware functions: Besides being an intermediary between software applications, middleware programs also do the following:
- Provide a secure communication channel between distributed applications so that websites send sensitive information safely to backend applications.
- Manage traffic flow and avoid overwhelming a particular application or file server.
- Automate and customize responses to the request. For example, the middleware sorts and filters the results before sending them to the front-end application.
Middleware Use Cases
As a broad category, middleware can encompass everything from web servers to authentication systems to messaging tools. Here are a few of the common use cases for middleware in modern development.
- New application development: Middleware can support modern and popular runtimes for a variety of use cases. Developers and architects can work with agility across platforms, following sets of foundational runtimes, frameworks, and programming languages. Middleware can also deliver commonly used functions such as web servers, single sign-on (SSO), messaging, and in-memory caching.
- Optimization of existing applications: Middleware can help developers transform legacy monolithic applications into cloud-native applications, keeping valuable tools active with better performance and more portability.
- Comprehensive integration: Middleware integration tools connect critical internal and external systems. Integration capabilities like transformation, connectivity, composability, and enterprise messaging, combined with SSO authentication, make it easier for developers to extend capabilities across different applications.
- Application Programming Interfaces (APIs): Many middleware services are accessed through APIs, which are sets of tools, definitions, and protocols that allow applications to communicate with each other. APIs make it possible to connect completely different products and services through a common layer.
- Data streaming: While APIs are one way to share data between applications, another approach is asynchronous data streaming. This replicates a data set in an intermediate store, where the data can be shared among multiple applications. One popular open-source middleware tool for real-time data streaming is Apache Kafka.
- Intelligent business automation: Middleware can help developers, architects, IT, and business leaders automate manual decisions. Automation can improve resource management and overall efficiency.
Service Oriented Architecture (SOA)