Spring Cache (In-Memory)

https://github.com/spring-boot-tutorials/spring-cache-in-memory

In this article we will configure Spring Boot to connect to a Cassandra database.

Spring Boot supported cache providers:

• Generic

• JCache (JSR-107) (EhCache 3, Hazelcast, Infinispan, and others)

• Hazelcast

• Infinispan

• Couchbase

• Redis

• Caffeine

• Cache2k

• Simple

Create Initial Code Base

• Go to https://start.spring.io/

• Add the following dependencies:

  • spring-boot-starter-cache

  • spring-boot-starter-web

  • lombok

• Click Generate

Dependencies

Dependencies used in pom.xml

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-cache</artifactId>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <optional>true</optional>
</dependency>

Configuration

Let’s create a new file src/main/java/com/example/spring_cache_abstraction/DefaultConfig.java

@Configuration
@EnableCaching
public class DefaultConfig {

    public static final String CACHE_ADDRESS = "addresses";
    public static final String CACHE_DIRECTORY = "directory";

    @Bean
    public CacheManager cacheManager() {
        SimpleCacheManager cacheManager = new SimpleCacheManager();
        cacheManager.setCaches(Arrays.asList(
                new ConcurrentMapCache(CACHE_DIRECTORY),
                new ConcurrentMapCache(CACHE_ADDRESS))
        );
        return cacheManager;
    }
}

Model

Let’s create a new POJO src/main/java/com/example/spring_cache_abstraction/Customer.java

@Getter
@Setter
@NoArgsConstructor
@AllArgsConstructor
@SuperBuilder
public class Customer {
    private String name;
}

Service

Let’s create a service class src/main/java/com/example/spring_cache_abstraction/DefaultService.java:

@Service
public class DefaultService {

    ///////////////
    // CACHEABLE //
    ///////////////

    @Cacheable(value = CACHE_ADDRESS, key = "#customer.name")
    public String getCachedAddress(Customer customer) {
        System.out.println("inside cacheable function `getCachedAddress`");
        return "address + " + customer.getName();
    }

    @Cacheable(value = CACHE_DIRECTORY, key = "#customer.name")
    public String getCachedDirectory(Customer customer) {
        System.out.println("inside cacheable function `getCachedDirectory`");
        return "address + " + customer.getName();
    }


    /////////////////
    // CACHE EVICT //
    /////////////////

    @CacheEvict(value = CACHE_ADDRESS, allEntries = true)
    public void evictAllAddress() {}

    @CacheEvict(value = CACHE_ADDRESS, key = "#customer.name")
    public void evictSingleAddress(Customer customer) {}


    ///////////////
    // CACHE PUT //
    ///////////////

    // @CachePut is used to ensure that a method is always executed
    // and its result is then placed into the cache. Unlike @Cacheable,
    // @CachePut does not skip method execution if a value is already
    // present in the cache. Instead, it forces the method to run, and the
    // result of that execution is used to update the corresponding entry
    // in the cache. This is useful for scenarios where you need to guarantee
    // that the cache always reflects the latest state of data, such as
    // after an update operation.

    @CachePut(value = CACHE_ADDRESS, key = "#customer.name")
    public String getAddressAndCache(Customer customer) {
        System.out.println("inside cacheable function `getAddressAndCache`");
        return "address + " + customer.getName();
    }


    /////////////
    // CACHING //
    /////////////

    @Caching(evict = {
            @CacheEvict(value = CACHE_ADDRESS, allEntries = true),
            @CacheEvict(value = CACHE_DIRECTORY, allEntries = true),
    })
    public void evictAllAddressAndDirectory() {}

    @Caching(
            cacheable = {
                    @Cacheable(CACHE_ADDRESS),
                    @Cacheable(value = CACHE_DIRECTORY)},
            put = {
                    @CachePut(CACHE_ADDRESS),
                    @CachePut(CACHE_DIRECTORY),}
    )
    public void unintelligible() {}


    /////////////////////////
    // Conditional Caching //
    /////////////////////////

    @CachePut(value="addresses", condition="#customer.name=='Tom'")
    public String getAddressConditional1(Customer customer) {
        return null;
    }

    @CachePut(value="addresses", unless="#result.length()<64")
    public String getAddressConditional2(Customer customer) {
        return null;
    }

}

Main

Now let’s use this service.

Go back to MainApplication.java and add the following:

@SpringBootApplication
public class SpringCacheAbstractionApplication implements CommandLineRunner {

    public static void main(String[] args) {
            SpringApplication.run(SpringCacheAbstractionApplication.class, args);
    }

    @Autowired
    DefaultService defaultService;

    @Override
    public void run(String... args) {
            List<Customer> customers = List.of(
                            new Customer("marcus"),
                            new Customer("jesus"),
                            new Customer("marcus"),
                            new Customer("jesus"),
                            new Customer("asher"));

            System.out.println("\nSTART ADDRESSES");
            customers.forEach(c -> {
                    System.out.println("Invoking cacheable function `getCachedAddress` for input param=" + c);
                    defaultService.getCachedAddress(c);
            });

            System.out.println("\nSTART DIRECTORY");
            customers.forEach(c -> {
                    System.out.println("Invoking cacheable function `getCachedDirectory` for input param=" + c);
                    defaultService.getCachedDirectory(c);
            });
    }
}

Run Application

Open terminal at project root and execute the following:

mvn spring-boot:run

There should be no errors and verify the output.