Blog ›Caching with Spring Boot and Hazelcast

By Rafal Leszko

Cloud Software Engineer

Rafał is a passionate software engineer, trainer, conference speaker, and author of the book, Continuous Delivery with Docker and Jenkins. He specializes in Java development, cloud environments, and continuous delivery. Prior to joining Hazelcast, Rafał worked with a variety of companies and scientific organizations, including Google, CERN, and AGH University of Science and Technology.

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Jul 13, 2020

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Caching with Spring Boot and Hazelcast

NOTE: This is an updated version of a previous blog. This article contains current information.

Spring Boot is very well integrated with Hazelcast. It’s enough to provide Hazelcast configuration on the classpath and it will be automatically used. In this blog post I’ll explain step-by-step how to enable Hazelcast as a cache manager for your Spring Boot application.

Source code from this blog is posted on the Hazelcast guide repository on Github.

Spring Boot Application

To use caching in your Spring Boot application, you need to:

  • add org.springframework.boot:spring-boot-starter-cache dependency
  • add @EnableCaching annotation to your main class
  • add @Cacheable("books") annotation to every method you want to cache

For more explanation on the Spring Boot cache topic, please check the official Caching Data with Spring guide.

In our case, let’s have a simple web service with two classes defined as follows.

// BookController.java
@RestController
@RequestMapping("/books")
public class BookController {
    @Autowired
    private BookService bookService;

    @GetMapping("/{isbn}")
    public String getBookNameByIsbn(@PathVariable("isbn") String isbn) {
        return bookService.getBookNameByIsbn(isbn);
    }
}
// BookService.java
@Service
public class BookService {
    @Cacheable("books")
    public String getBookNameByIsbn(String isbn) {
        return findBookInSlowSource(isbn);
    }

    private String findBookInSlowSource(String isbn) {
        // some long processing
        try {
            Thread.sleep(3000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return "Sample Book Name";
    }
}

If we started the application, then every call to the endpoint /books/<isbn> would go to the method findBookNameByIsbn() which in turn would first check the cache. Only if it does not find value in the cache, the method findBookInSlowSource() would be executed.

Using Hazelcast as Cache Manager

We want to use Hazelcast as the cache manager. The good news is that all you have to do it to add Hazelcast to your classpath.

<!-- pom.xml -->
<dependency>
    <groupId>com.hazelcast</groupId>
    <artifactId>hazelcast-all</artifactId>
    <version>4.0.2</version>
</dependency>

Then, you need to add Hazelcast configuration in one of the following manners:

  • Add hazelcast.yaml configuration OR
  • Add hazelcast.xml configuration OR
  • Define @Bean with Hazelcast configuration in the source code

Let’s use the first option and add the following file into src/main/resources.

# hazelcast.yaml
hazelcast:
  network:
    join:
      multicast:
        enabled: true

No more configuration needed, Hazelcast is already used as the cache manager in your project!

Starting the Application

To start the application, run the following command.

mvn spring-boot:run

You should see in the logs that embedded Hazelcast has started.

Members {size:1, ver:1} [
        Member [172.30.63.9]:5701 - 75cd0b19-ee36-4e0a-9d9c-38c49f67f842 this
]

Testing the Application

You can test the application by executing the following command.

curl locahost:8080/books/12345
Sample Book Name

The first time you execute this command it should take some time to get the response. However, when you try it again, it’s instant. That means that the cache is used.

curl locahost:8080/books/12345
Sample Book Name

What’s more?

Spring Boot is really well integrated with Hazelcast and vice-versa. If you want to use Hazelcast in the client-server topology, then it’s enough if you create hazelcast-client.yaml file instead of hazelcast.yaml on your classpath. And that’s it! You configured Hazelcast client.

To read more check out the official documentation Spring Boot: Hazelcast.

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