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According to Statista, 85% of respondents from large organizations with over 5,000 employees state currently using Microservices in their development environments in 2021. Larger organizations prefer the use of microservices in their operations because of the myriad of benefits they offer.
Source: Statista
Due to their wide adoption, microservices are now the ‘new normal’ for developers and organizations. For every developer, especially Java developers, Microservices have become an essential skill.
This article guides those who want to learn about Java Microservices, frameworks, Java Microservice examples, and interview questions related to them.
Let’s start with an overview of Java Microservices.
What are Java Microservices?
Java Microservices refers to Java applications composed of small, independently deployable, and loosely coupled services.
To understand this better, let’s first learn what microservices are.
Microservices are a design pattern and a variant of the Service-Oriented Architecture style. Each Microservice is a small, independent piece of an overall more extensive system. Microservices are designed to complete a specific task independent of size or domain. Changing a small part of the application doesn’t require rebuilding and redeploying the whole application; it only requires changing one or a few microservices.
The architecture of microservices looks like this:
The microservice architecture allows the development of an application as a set of separate services. Different services can be written in different programming languages and managed by cross-functional teams. Each service is independently deployable and scalable, providing excellent governance, scalability, and reliability.
What Makes Java a Good Choice for Microservices?
Java is the best language for microservices.
Microservices can be implemented with several frameworks, tools, and languages. Java is one of the best languages for microservices apart from Python, C++, Ruby, and Golang.
Here are some factors that justify why we use microservices in Java. Later, we will see how microservice architecture is proper and what benefits it offers.
Well-suited Standards and Syntax
Annotations in Java are developer-friendly and easy to read. When using microservices in Java, these annotations make things easier for the developer. In addition, many Java EE standards support microservice architecture, such as JPA for data handling, JAX-RS for APIs, CDI(Contexts and Dependency Injection) for component and lifecycle management, and so on.
Java is more suitable for working with complex systems because of its readability. The structure of Java application development supports developing and deploying microservices without additional overhead.
A Wide Community
Java has existed for an extended period.
Being one of the oldest and broadest communities, Java has many resources, libraries, and frameworks. Java is predominantly used for enterprise application development, backend development, web applications, mobile, big data, cloud, AI, and scientific apps.
Because of JVM, Java applications are platform-independent. This makes Java worthwhile and one of the most popular programming languages for critical applications worldwide.
Java developers are easy to find. Microservices are also an essential skill for Java developers, as Java-based microservices are easy to scale and widely used by organizations.
Frameworks
Several frameworks are available for developing microservices in Java. These frameworks make work easier and faster. Spring Boot, Jersey, DropWizard, and Spark are some popular Java microservices that Java developers use.
These frameworks simplify the configuration and setup process and help developers communicate between microservices. Other publish/subscribe systems are also helpful in building microservice applications.
Monolith to Microservice
Java is extensively used in Microservices and vice versa. Many enterprises use Java, and constant changes are required to meet modern-day challenges. If an entire application wants to adopt new technology or a framework, it must be rewritten. This would not be feasible as developing, testing, and deploying large applications requires time, resources, and cost.
New updates are often required in a modern-day environment where more than one technology or tool is used. In this case, choosing microservice architecture in Java helps you deliver new features quickly, eases complexity, achieves scalability, and allows you to choose the technology stack that best fits your requirements.
Now, let’s quickly go through the benefits of microservices architecture.
Advantages of Microservices
Let’s look at several benefits of microservices in general.
Scalability
Microservices are small components that are easy to build, deploy, and update. Based on the requirements, microservices are easy to scale up and down. As each microservice is easily manageable and independent, the cost of scaling is also significantly lower compared to the monolith.
Flexibility
Microservices allow developers to choose the right tool or language for a particular task. The constantly changing technology landscape, modern-day business demands, and a constant race to provide users with the best user experience significantly contribute to the frequent changes in software development.
With microservices, developers can choose different technologies for different services. This is useful when adopting new technologies and tools to meet demands. This would not be technically easy if it were a monolithic application.
Resiliency
If one of the application’s components fails, it will be less likely to impact the entire stack. Each microservice runs independently, improving fault isolation. If this were a case in Monolithic, one change would require redeploying the whole application. Frequent changes and deployments are more accessible with Microservices.
Faster Time To Market
This is one of the critical advantages of microservices. There can be multiple distributed, autonomous teams; each is responsible for developing and managing one or more microservices. Cross-functional teams can collaborate and establish microservices independently, resulting in faster development and increased productivity.
Maintainability
Remember the divide and conquer rule? Yes, that perfectly fits this scenario. Each microservice is relatively small, independent, and easier to change. This means microservice architecture offers improved code maintainability, testability, and deployment.
After seeing the microservices benefits, let’s move to see the Java Microservice Example.
Java Microservices Example
This is an example of a Java microservice with REST API. You can create as many services as you want with REST endpoints per your requirements and architecture.
import org.springframework.boot.*;
import org.springframework.boot.autoconfigure.*;
import org.springframework.stereotype.*;
import org.springframework.web.bind.annotation.*;
@RestController
@EnableAutoConfiguration
public class HelloWorld {
@RequestMapping("/")
String example() {
return "Welcome to SPEC INDIA!";
}
public static void main(String[] args) throws Exception {
SpringApplication.run(HelloWorld.class, args);
}
}
Output:
Welcome to SPEC INDIA!
You might have a question regarding how to develop microservices in Java. Here are some of the best Java microservices frameworks that make your job easier.
Best Java Microservices Framework
Spring Boot
Spring Boot Microservices in Java became the de facto standard. It is one of the top Java microservices frameworks widely used by developers. Spring Initializr, Spring Cloud, and Spring Boot’s embedded server model help developers quickly build microservices by simplifying many of the tasks for configuration and setup.
Dropwizard
Dropwizard is a Java microservices framework for developing high-performance RESTful web services. It provides developers with tools and frameworks for building Java microservices. Dropwizard gathers stable and mature Java libraries into a lightweight package so you can quickly start creating applications.
Spark
Spark is one of the best Java microservices frameworks for creating web apps in Java 8 and Kotlin. This micro web framework allows developers to start rapidly and with minimal effort. Sinatra, a famous Ruby micro-framework, inspired it.
Jersey
Jersey framework is an open-source framework for developing RESTful web services in Java. It makes it easy for developers to build RESTful web services using Java and JVM. It offers support for JAX-RS APIs and serves as a JAX-RS Reference Implementation that simplifies the development of RESTful services.
Swagger
Swagger helps developers document APIs. It is an interface description language that describes RESTful APIs expressed using JSON. Swagger is a set of open-source software tools that allow developers to quickly build, design, document, and use RESTful web services.
Many companies widely use it to deliver great APIs and streamline API development.
Restlet
Restlet framework helps Java developers create better Java APIs using the REST architecture style. It is an open-source framework widely used by developers to develop secure and scalable web APIs. It offers robust routing and filtering capabilities, numerous extensions, and a unified client and server Java API. It is available for all major platforms.
Microservices are a typical and widely adopted software design pattern, so they are considered one of software developers’ top skills regardless of the technologies or frameworks they use.
Here are some top Java microservices interview questions mostly asked in interviews for Java developers or Java-related tech roles.
Java Microservices Interview Questions
- What is microservice architecture? What do you understand by Microservices?
- What are the main features of Microservices?
- Can you explain some benefits of Microservices?
- Differentiate Monolith and Microservice architecture.
- What are Spring Cloud and Spring Boot?
- What are the cons of using Microservices?
- Have you faced any challenges while working with microservices? If yes, explain how you solved them.
- What is Cohesion?
- Name three standard tools used for microservices.
- What do you mean by continuous delivery?
- In which cases is microservice architecture best suitable?
- What are the different strategies used in Microservice deployment?
- Explain Domain-Driven Design.
- What is the difference between Cohesion and Coupling?
- What is the use of containers in Microservices?
- What is Contract Testing?
- What is the difference between Monolithic, SOA, and Microservices Architecture?
- Why is Java a preferred language for implementing microservices?
- What is a distributed transaction?
- Name popular Java microservice frameworks.
- What is a Client certificate, and where is it used?
- What do you mean by Semantic Monitoring?
- Can you explain how microservices communicate with each other in Java?
- Do you know some famous companies that are using microservice architecture?
- What is RESTful?
- What is end-to-end microservice testing?
- Explain three types of tests for microservices.
- What is the use of Docker?
- What is the CDC?
- What do you mean by Bounded Context?
