Blog
June 17, 2025
A hybrid of diverse technologies and disparate endpoints comprise the modern IT landscape. Middleware unifies and connects these systems, and today enterprises have a variety of commercial and open source middleware tools to choose from. But which middleware technologies are best for the job — and should you be paying for them?
In this blog, we give an overview of middleware, including the different types of middleware technologies, how they are used, and why teams should consider switching to open source middleware tools.
What Is Middleware?
Middleware is a broad category of software that encompasses any type of software used to connect one system to another, or one layer to another.
Middleware can be described variously as “glue”, as a conduit, or as an adapter that connects and links different systems. Some middleware also provides a platform or foundation to build applications, providing common functionality and connectivity so application development can focus on unique requirements. Common categories of middleware include web servers, application servers, content management systems, messaging and service buses, and other integration frameworks and services.
Types of Middleware Technologies and Middleware Tools
Since middleware can encompass most any software between the OS and application layers, there are many different categorizations — both based on how it is used and by location in a typical application architecture. Some common categories include the following:
Message-Oriented Middleware
One of the most pervasive pieces of middleware, message-oriented middleware (MOM), includes message queues, message brokers, and message streaming platforms. Message-oriented middleware focuses on reliably routing and delivering message-based traffic to connect disparate applications and systems. Some MOM platforms are also able to transform and translate messages to enable communication between applications written in different languages or using different protocols. MOM also helps decouple applications and enables asynchronous and decoupled communication across large architectures.
Remote Procedure Call Middleware
Remote Procedure Call (RPC) middleware is used to act as a conduit for synchronous or asynchronous service calls between different systems.
AI Agent Middleware
AI Agent middleware is software that acts as a link between AI models and the applications that use them. Applications can then benefit from AI analysis, insights, and automation.
Application Server Middleware
Application server middleware consists of standard application servers used to deploy, run and manage enterprise applications. They often provide additional support in terms of standardizes libraries/APIs (like J2EE or .NET), and standardized configuration (security, logging, and management).
Web Middleware
Web middleware includes traditional http servers such as Apache and Nginx, used for serving static resources quickly and reliably, or acting as an intermediary between clients and application servers or services.
ORB Middleware
Object Request Broker (ORB) middleware brokers request between applications using a standardized object representation. CORBA (Common Object Request Broker Architecture) is one example of this type of middleware.
Transaction Processing Middleware
Transaction processing middleware is generally service-based and supports executing transactions across a distributed set of applications. This type of middleware allows for executing business and other processes in a step-by-step fashion with guarantees execution of the proper application steps in order and can also provide the ability to roll back a transaction if an error occurs.
Back to topWhat Is Middleware Used For?
Middleware is fundamentally a bridge, and can be defined as any software that bridges two or more other systems. This can be across architectural layers — like an interface between applications and storage (a database). This can also be in the form of frameworks and APIs that provide efficient communication between or even within an application.
Middleware standardizes and simplifies integration of different components to assemble a comprehensive solution to a problem. The popularity of common middleware packages mean they are proven in production and are well supported.
Middleware can also support application development by providing prebuilt functions for integration such as single-sign-on, messaging, caching, common design pattern implementation and other common functions. Middleware is also used extensively when connecting and integrating with legacy systems — by providing adapters, APIs, transformations, and messaging, new development can happen around legacy systems rather than all at once.
Middleware connections to legacy systems can enable migration to modern architectures with higher performance and higher reliability.
Back to topCommercial Middleware vs. Open Source Middleware
Commercial, comprehensive middleware offerings like IBM WebSphere (which includes IBM MQ) can come at an enormous price tag for organizations — especially at scale. With a sub-capacity pricing model, and a contractual delineation between license costs and support costs, larger organizations can quickly find their annual costs moving above seven figures.
There are less expensive commercial middleware options, but all commercial software (especially within large ecosystems like Red Hat, Oracle, or IBM), carries the risk of vendor lock-in. Any short-term benefits get overshadowed by the eventual cost of moving on from that ecosystem, and the potential for burgeoning contract costs from the commercial provider.
That’s not to say that open source software isn’t without costs of its own. Open source requires a high degree of expertise in order to fully utilize it, either in-house or from a third party like OpenLogic that can provide open source middleware support.
In terms of technological capability, open source software is the clear leader — with popular options like ActiveMQ, Camel, Kafka, and others that can fulfill and exceed the functionality of their all-in-one commercial counterparts. Ultimately, choosing between commercial and open source comes down to the needs of the organization, the state of their underlying IT infrastructure, and their capacity to work with and support that software.
Back to topConsidering Your Middleware Options?
Read our Decision Maker's Guide to Open Source Middleware for an overview of available options, and when to use them.
The Best Open Source Middleware Technologies
The best middleware technologies tend to be based on the needs of the user, but our team has a few versatile favorites we will explore in this section.
Apache Camel
Apache Camel is the industry standard for reducing boilerplate code for complex integrations, all while maintaining features like automatic error handling, redelivery policies, and the ability to handle complex aggregations. Apache Camel is a domain-specific language that’s an implementation of the Enterprise Integration Patterns (EIPs) and helps organizations solve a range of very specific problems.
Apache Camel provides a configuration syntax and runtime to configure EIPs within your application federation layers. By normalizing message data, providing easy transformation mechanisms, and giving developers pre-built components that manage message exchanges, nearly any endpoint imaginable can be integrated.
For developers interested in learning Apache Camel, OpenLogic offers in-depth, expert-led Apache Camel training courses. For an example of how Camel can be applied, this banking company case study is a good place to start.
Apache ActiveMQ
The Apache ActiveMQ project consists of two separate messaging technologies: ActiveMQ Classic and ActiveMQ Artemis. Both technologies are currently maintained and will continue to be for the foreseeable future. Artemis was at one point seen as the successor to Classic, but that is no longer the case. Still, Artemis is viewed as a more modern approach to messaging.
Both ActiveMQ technologies are mature and widely adopted messaging platforms, with thousands of companies relying on them. Businesses can adopt either ActiveMQ technology quickly, and their familiar concepts will be accessible to anyone comfortable with JMS. The two active communities and strong ecosystem continue to ensure long-term viability and relevance.
Compare IBM MQ vs. Kafka vs. ActiveMQ >>
Apache Kafka
Apache Kafka is a stream processor and can be used as a message broker as well. If architecture or software requires low end-to-end latency with exceptional durability (persistence), Kafka is the piece of software to provide this and other functionality. Whereas traditional message brokers focus on a pattern of allowing consumer applications to work on one piece of data at a time, Kafka allows for the analysis of lots of individual pieces of inflight data.
This makes Kafka an ideal candidate for implementing streaming analytics and Big Data applications. Designed at LinkedIn to scale to hundreds of millions of messages, though not as lightweight a solution as ActiveMQ, it is ideal for working on astronomically large datasets. Kafka is often used with Kafka Connect to pair with data sources and destinations.
Read Kafka Case Studies >>
Apache Tomcat
Apache Tomcat is an open source Java application server that is capable of powering enterprise-scale web applications. Though not a full-fledged JEE server, Tomcat was originally conceived as the reference implementation for the Java Servlet and Java Server Pages specifications.
Tomcat remains a fast and lightweight implementation, even relied upon in new “serverless” frameworks like SpringBoot as a runtime container because of its thin profile. For simple and lightweight Java web applications, as well as the emerging world of Java microservices, Tomcat remains the top choice for deployment.
See what's new in Tomcat 11 >>
Apache Pulsar
Apache Pulsar was developed originally by Yahoo! as an enterprise messaging platform and is a top-level Apache Foundation project. Pulsar is a feature-rich, scalable, low latency distributed messaging and streaming platform designed for large-scale environments. Its architecture separates the message processing functions (brokers) from the message storage functions (bookkeepers), so that it can scale horizontally in either component as needed.
Pulsar supports multiple types of messaging, including pub-sub and guaranteed delivery topics, providing functionality that otherwise requires multiple tools. Messages can be modified in flight through the use of custom functions. Pulsar also offers geo replication, enabling replication between multiple Pulsar clusters, and supports up to one million topics. Multitenancy is handled through the use of namespaces and access control policies.
Back to topFinal Thoughts
For organizations considering how to connect their data systems, harness their streaming data, or any other number of solutions middleware can provide, don't overlook the advantages that come with deploying open source middleware. As this blog hopefully demonstrates, open source middleware technologies can deliver considerable cost savings and more flexibility to organizations — if they have the necessary expertise in-house or partner with OpenLogic to manage them.
Get Technical Support for Middleware
When middleware is correctly implemented, you can boost IT security, system performance, and overall efficiency. OpenLogic provides open source middleware support, training, and consultations on critical requirements such as federating systems, proxying encrypted traffic, and extending legacy investments with web apps.