Java Microservices Tutorial

Building a Java Microservices Application 

Building a Java Microservices application requires you to create several independent services. You’ll implement architectural patterns to manage their communication and scaling. One common approach is to use Spring Boot to develop your microservices application and Kubernetes to deploy it.  

This step-by-step, high-level project tutorial outlines each step you will need to follow to create a basic Java microservices system. You’re going to focus on a single CRUD (Create, Read, Update, Delete) style of service as the foundation. In our tutorial, we use Spring Boot to build our core service, Azul Prime to optimize its runtime environment, and Kubernetes to deploy the application. 

Set Up the Core Microservice

First, you’re going to build the product service, which is a single, standalone Java service that’s responsible for one business domain and function, such as managing your product catalog. Follow these high-level steps: 

1. Set up your project. Generate the base project structure by using Spring Initializer (start.spring.io). You’ll need Spring Web, Spring Data JPA (Java Persistence API), a database driver (such as MySQL or PostreSQL), and Lombok (a Java library that generates common methods based on your class annotations). 

2. Build your data model. You’ll need to define your database entity for your service. Create a Product.java class and annotate it with @Entity and @Id from the Java Persistence API (JPA) to map it to the database table. 

3. Set your data access. Next, you’ll create the repository layer that will enable your service to communicate with the database. Define a ProductRepository interface that extends JpaRepository<Product, Long> for your application. Spring Data JPA automatically provides all the standard CRUD methods (to find, save, and delete), without needing to write any SQL. 

4. Build your business logic. This is where you implement the core service operations. Create a ProductService class, with the @Service annotation. Inject the ProductRepository and write methods for creating, reading, and updating your products (in this product catalog application). 

5. Create the RESTful endpoints. This exposes your service’s functionality. Create a ProductController class, with @RestController and @RequestMapping(“/products”) annotated. Define methods using @GetMapping, @PostMapping, @PutMapping, and @DeleteMapping to map your HTTP requests to the ProductService methods. 

Apply Interservice Communication and Resilience

Microservices architecture requires the services to interact and communicate with each other. You build resilience in your application when you protect your services from networking and communication issues. Apply these steps to set up your interservice communication and resilience:  

1. Initiate service discovery. Enable your services to find each other by name (such as ProductService) instead of by the hardcoded IP address. This makes a larger cluster of microservices easier to manage and avoids potential issues. You can use a Kubernetes service or Spring Cloud Netflix Eureka. (The latter is called that because Netflix created this open-source, foundational component of the Spring Cloud framework that implements the Service Discovery pattern in your microservices architecture.) The service registers itself upon startup. 

2. Enable a synchronous call. For example, you should set up Service A (such as the Order Service) to call Service B (such as the Product Service). You can use Spring Cloud OpenFeign or Spring WebClient to make reliable, non-blocking HTTP calls between your microservices. 

3. Provide resilience to protect against cascading failures. Integrate a Circuit Breaker library (such as Resilience4j). Then annotate the calling methods to protect against situations where the downstream service fails. This way, the caller immediately stops sending requests and returns a defined fallback response instead. 

Implement Containerization and Azul Integration for Performance Optimization  

Azul Prime addresses unique challenges that you’ll face when building a Java microservices application: issues around startup, memory, and latency. Follow these steps to ensure your microservices application has optimal performance and lowers your resource consumption (and the associated costs): 

1. Build containerization. You’ll likely start by packaging the Spring Boot JAR executable file for deployment. Create a Dockerfile that uses a base image that’s running Azul Zulu Prime JVM, which includes the C4 Garbage Collector (GC). (C4 stands for Continuously Concurrent Compacting Collector). Run the command: FROM azul/zulu-prime-jdk:17 

2. Configure your JVM. You’ll want to optimize the service for consistent, low latency. To activate the pauseless C4 GC, pass the following argument to the JVM in your Dockerfile’s ENTRYPOINT: -XX:+UseC4GC 

3. Optimize for resource efficiency. Update your resource allocation based on your actual CPU and memory needs. To do this, configure the JVM to manage its memory by using container-aware flags that allow your container orchestrator (such as Kubernetes) to assign accurate limits. 

4. Set up a faster startup and warmup capability. Implement the CNC and ReadyNow! features of Azul Prime to virtually eliminate your Java startup and warmup delays. Use environment variables or JVM flags to offload the JIT compilation. 

Build Orchestration and Resilience

Next, you’re going to integrate the optimized service into a managed container environment, leveraging the predictable performance gained from Azul Prime. Follow these steps: 

1. Use Kubernetes orchestration to deploy the containerized service(s). You can write deployment YAML files. Thanks to Azul Prime’s efficiency capabilities, you can set the resources.limits and resources.requests for lower CPU and memory usage than you’d get with a standard OpenJDK service. 

2. Set up service discovery. Use the internal DNS in native Kubernetes services to handle service discovery. 

3. Implement resilience to handle downstream failures. Implement a Circuit Breaker library (such as Resilience4j) in your calling service. Thanks to Azul’s C4 GC, the low-latency of your product service ensures it is less likely to accidentally trigger the Circuit Breaker in other services. 

4. Deploy an API gateway to route external traffic. You can use a Spring Boot service using Spring Cloud Gateway to configure routing rules that forward your traffic, such as setting the requests to /api/products to go to the ProductService.  

By following these steps, you’ll be able to build a Java microservices application. 

Azul Prime 

Java developers building microservices can use Azul Prime to solve major performance and consistency issues that are inherent when running a distributed Java application. To learn more about how Prime can provide you with a high-performance JVM, see Azul Prime: High Performance JVM.