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Microservices in Java


By RevDeBug

It’s no secret that microservices are a formidable and popular architectural approach to software development. The small and independent services that talk to each other via application programming interfaces (APIs) make for speedy development and simplified scaling, ultimately reducing the time taken to release products.

Now couple this concept with Java, one of the most coveted programming languages and you have something worth giving a try. But before we dive into microservices in Java, let’s first explore the idea that precedes them, i.e. Java monoliths.

What are Java monoliths?

A monolithic architecture is one where all processes are closely grouped and run in a single unit. In that regard, Java monoliths can be simply described as software built using Java, that runs as a single unified piece.

A typical Java monolith will have all the code needed to perform a specific action or set of actions within one .jar or .war file. This file can be run on a server and be the one element you need to deploy a Java application.

Where do Java monoliths fall short?

Java monoliths aren’t necessarily very flawed as an idea, but they can become inadequate as time goes by. Firstly, if an organization grows and starts to offer more products or services, the software used to deliver all that functionality has to grow too.

In the case of Java monoliths, if you find yourself needing to add to your software, you may occasionally have to bring in different developers and other personnel to contribute to the monolith. As more and more of them add to it or tweak it in some way, the codebase will eventually become much larger and probably less comprehensible.

Over time, fears can emerge regarding the deployment of this one very large block since some contributors don’t know how well their additions work with the rest of the block. The file will also take up more space and you’ll have to keep overhauling the entire block with every minor change you want to make.

To improve the way you build, deliver and maintain Java applications, you can take the approach of Java microservices.

So what are Java microservices?

Java microservices are a group of small software applications built in Java, each with minimal functionality, that can run independently and also work together as part of a larger solution. A Java microservice usually has a name indicating its purpose and can often be used by different software systems that need its capability.

For example, one microservice may be built solely for the purpose of calculating percentage net profit. This microservice can be used by someone doing in-depth accounting work, and also be utilized by another person who’s simply tracking an investment portfolio on a mobile app.

There’s often some contention regarding the question of what qualifies as a microservice. For instance, what is the maximum number of classes that can be in one unit for it to be referred to as a microservice? The reality is that some microservices can be very simple and lean, while others may have a number of processes.

Ultimately, it’s better to focus on the deployment aspect. If a service can be deployed separately, then it can qualify as a microservice. Additionally, it is important to put emphasis on the structure of the system to ensure that all subtasks are clearly laid out and the system can identify which one requires a specific microservice.

There are various Java-based frameworks that can be used to build Java microservices such as Swagger, Spring Boot, and Jersey.

Communication between Java microservices

There are two ways in which Java microservices can communicate, namely; synchronous communication and asynchronous communication.

Synchronous communication

This type of communication typically happens via HTTP and REST-like services which return JSON or XML. REST communication is ideal when you need an instant response. For example, if a user is opening an account, they may be required to verify their identity, a step without which they can’t get an account.

In this scenario, a microservice that scrutinizes photos and identification document features can be called upon using synchronous JAVA REST calls.

Asynchronous communication

This kind of communication is commonly done by messaging with the help of a Java Message Service, and in some cases, a protocol like AMQP. It is good for situations where you don’t need an immediate response.

This can be something like helping a user to get a preview or quotation for items or services that they intend to buy. It is a step that isn’t integral to confirming a purchase.

Use cases for Java microservices

Java microservices can be used in reporting systems, with the necessary steps like data collection, aggregation, cleansing, and more all having their respective microservices. The workflow will come with a clear footprint that can be tracked to find out which microservice caused an issue in the data if there’s any.

These microservices can also be used in machine learning (ML) environments. They can help to handle a data flow so that an ML framework can generate a result. The beauty of this approach is that you can include multiple ML frameworks in the workflow to generate numerous models on the same data.

By doing so, you can determine which model is giving the best results when targeting a forecasted outcome. There are a number of ML frameworks that can be used with Java such as Apache Mahout, TensorFlow, and Apache SInga.


While Java microservices can help you enhance the experience for those using your software systems, it is not as straightforward as it may sound. To realize a successful microservice architecture, developers need to polish their monolith-oriented skills, along with other best practices.

This is partly because microservice architecture may not always be started from scratch. Sometimes, a monolith can be disintegrated to make some processes run independently. Such an approach would need developers to be able to comb through the original code and learn how best to handle the new communication needs.

It also helps to get assistance from specialists or experts in certain fields/industries when embarking on a software development project so that you can practice domain-driven design.

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