What is middleware?

Middleware streamlines application development and speeds time to market through intelligent functions that facilitate connections between platforms that initially were not designed to connect.

Various types of middleware include the following:

• Message brokers or transaction processing monitors that focus on a kind of communication.
• Web application servers or mobile device middleware that provide the full range of communication and connectivity capabilities that are needed to build a particular type of application.
• Cloud-based integration platform as a service (iPaaS) or an enterprise service bus (EBS) that functions as a centralized integration hub for connecting all the components in an enterprise.
• Middleware that allows developers to build their own customized middleware.

The term middleware was first introduced in the late 1960s. It was coined because the initial version typically acted as a mediator between an application front-end (client) and a back-end resource. This resource might be a database, mainframe application or specialized hardware device from which the client might request data. In response to the increase in distributed computing in the 1980s, middleware use increased as a way to link newer applications to traditional legacy systems.

But today's middleware operates well beyond this scope. Portal middleware, for example, encompasses the application front-end as well as tools for back-end connectivity. Database middleware typically includes its own data store.

Middleware has evolved to play an essential role in modern cloud-native application development. It uses container technology, which allows DevOps and other teams to connect to resources distributed across multicloud environments. This supports continuous integration (CI) and continuous delivery (CD)—CI/CD—thus streamlining application coding, testing and deployment for rapid scaling and business growth.

Enterprises are increasingly tapping into middleware as a cloud-based service offering for communication between systems and as a data management tool. A study from Technavio projected the global middleware as a service (MWaaS) market to increase by USD 45.44 billion, at a compound annual growth rate (CAGR) of 17.73% in 2023—2028. The study attributes this growth to the widespread adoption of cloud computing and an increase in serverless computing and microservices.¹

Middleware enables developers to build applications without creating a custom integration whenever they need to connect to application components (services or microservices), data sources, computing resources or devices.

Middleware facilitates communication between different applications and services by providing essential services. It achieves this communication through common messaging frameworks, such as JavaScript object notation (JSON), representational state transfer (REST), extensible markup language (XML), simple object access protocol (SOAP) or web services. Typically, middleware also provides services that enable components written in multiple languages—such as Java, C++, PHP and Python—to talk with each other.

Standard middleware architectural components include the following:

• Middleware management console: The management console gives developers an overview of middleware events, activities, configurations and so on.

• Client interface: The client interface on the front-end communicates with back-end applications, databases microservices or other services.

• Middleware internal interface: The middleware internal interface allows middleware instances to communicate with each other using a special middleware protocol.

• Platform interface: The platform interface connects to back-end servers and different operating systems (OSs), ensuring middleware functions across platforms.

• Contract manager: The contract manager defines the data exchange rules that applications must follow.

• Session manager: The session manager ensures secure communication between middleware and applications and ensures that they are not timed out.

• Database manager: The database manager provides integration with different databases based on specific requirements (for example, on premises or cloud-based data).

• Runtime monitor: The runtime monitor tracks all middleware data movements and provides activity reports for software developers.

In addition to providing work-saving interoperability, middleware services help software developers in the following ways.

There are many different types of middleware. Some focus on specific types of connectivity, others on particular applications, application components and devices. Some combine middleware capabilities for a specific software development task. Here are some of the best-known and most commonly used types of middleware software:

• Message-oriented middleware (MOM)
• Remote procedure call (RPC) middleware
• Data or database middleware
• Application programming interface (API) middleware
• Object request broker (ORB) middleware
• Transactional middleware
• Asynchronous data streaming middleware
• Device middleware
• Portal middleware
• Robotics middleware
• Enterprise application integration middleware

Message-oriented middleware (MOM) enables application components that use different messaging protocols to communicate and exchange messages. In addition to translating or transforming messages between applications, MOM manages the routing of the messages, so they get to the proper components in the appropriate 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, whether on the same computer or a different computer or network. This process makes both applications function as if they 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.

Application programming interface (API) 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 different 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 its fulfillment by another object or component. This process occurs within the distributed network, ensuring seamless communication and interaction between components.

Object request brokers (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 user interface (UI) looks like. The "brokering" mechanism manages 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 drive transactions from one step to the next. They manage the data exchange by adding, changing or deleting data as needed until the transaction reaches 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 open source platforms for real-time event streaming.

Device middleware provides a focused set of integration and connectivity capabilities for developing apps for a specific mobile operating system (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 integration of robotic hardware, firmware and software from multiple manufacturers and locations.

There are two basic classes of middleware: enterprise application middleware and platform middleware.

Enterprise application integration middleware enables an organization to establish an enterprise integration hub. This system provides a standardized way to connect all applications, application components, business processes and back-end data sources throughout the extended enterprise.

Until about a decade ago, the most prevalent enterprise application integration middleware was the enterprise service bus (ESB), which served as the integration hub within a service-oriented architecture (SOA).

Today, integration platform as a service (iPaaS) allows an organization to connect applications, data, processes and services across a hybrid cloud—the combination of on-premises, private cloud and public cloud environments. This solution helps organizations avoid the work and expense of purchasing, installing, managing and maintaining the integration middleware (and the hardware it runs on) within its own data center.

Major cloud service providers (CSPs) such as Microsoft Azure, Google Cloud, Amazon Web Services (AWS) or IBM Cloud®, all offer iPaaS solutions.

Platform middleware (or application platform middleware) supports application development. It accelerates application delivery by providing a runtime hosting environment—such as a Java runtime environment (Java RE), containers or both—for application or business logic. Platform middleware can include or combine enterprise application servers, web servers, content management systems (CMSs) and other middleware types previously mentioned.

Both integration platform as a service (iPaaS) iPaaS and platform as a service (PaaS) are cloud-based computing solutions that serve different purposes. Whereas iPaaS focuses on enabling app, device and system integration, PaaS provides organizations with a platform for building, running and managing applications.

PaaS is a choice for small businesses and startups with limited IT budgets as it allows teams to build apps cost-efficiently compared to creating in-house development platforms. iPaaS is a better choice for large organizations and enterprises running complex, dynamic architectures.

That said, iPaaS services often work together with cloud services, including PaaS and software as a service (SaaS). For instance, organizations might combine iPaaS with PaaS (for example, Cloud Foundry, Red Hat OpenShift) or SaaS (GitHub) development solutions.

Cloud-native is an application development approach that uses fundamental cloud computing technologies to provide consistent development, deployment and management across hybrid cloud environments.

Today's cloud-native applications are built from microservices and deployed in containers that use Kubernetes, a widely-used container orchestration platform.

Microservices are loosely coupled application components that encompass their own stack and can be deployed and updated independently of one another. They communicate by using a combination of REST APIs, message brokers and event streams.

Containers are lightweight execution tasks that package application code, such as microservices, together with just the OS libraries and dependencies needed to run that code on any cloud or traditional IT infrastructure.

Together, these and related technologies create a powerful, develop-once-deploy-anywhere platform for delivering net-new hybrid cloud applications and modernizing traditional legacy systems for use in the cloud. However, they also lead to a complex development environment that combines even more software applications, data sources, programming languages, tools and distributed systems.

Middleware can resolve some of this complexity. However, running containerized applications with conventional middleware can add complexities of its own, including the infrastructure overhead that containers were designed to eliminate. For this reason, cloud application development platforms include containerized or modularized middleware so that only the required connectivity functions can be packaged in a container.