1package com.demo.project98.service;
 2
 3import com.demo.project98.domain.Country;
 4import lombok.extern.slf4j.Slf4j;
 5import org.springframework.cache.annotation.CacheEvict;
 6import org.springframework.cache.annotation.CachePut;
 7import org.springframework.cache.annotation.Cacheable;
 8import org.springframework.stereotype.Service;
 9
10@Service
11@Slf4j
12public class CountryCache {
13
14    /**
15     * NOTE: Never create a local HashMap to key those values, as it can cause memory overflow without eviction.
16     *
17     * @Cacheable - If key is present returns the object, no update happens.
18     * @CachePut - If key is present it will update and then return object.
19     */
20    @Cacheable(cacheNames = "countryCache", key = "#country.code")
21    public Country get(Country country) {
22        log.info("Getting country name: {}", country.getCode());
23        return country;
24    }
25
26    @CachePut(cacheNames = "countryCache", key = "#country.code")
27    public Country put(Country country) {
28        log.info("Adding country: {}", country);
29        return country;
30    }
31
32    @CacheEvict(cacheNames = "countryCache", key = "#country.code")
33    public void evictSingleCacheValue(Country country) {
34        log.info("Evicting from cache: {}", country);
35    }
36
37}

 1package com.demo.project98.service;
 2
 3import com.demo.project98.domain.Country;
 4import lombok.extern.slf4j.Slf4j;
 5import org.ehcache.event.CacheEvent;
 6import org.ehcache.event.CacheEventListener;
 7
 8@Slf4j
 9public class CountryCacheListener implements CacheEventListener<String, Country> {
10    @Override
11    public void onEvent(CacheEvent<? extends String, ? extends Country> event) {
12        log.info("Event '{}' fired for key '{}' with value {}", event.getType(), event.getKey(), event.getNewValue());
13    }
14}

 1package com.demo.project98;
 2
 3import com.demo.project98.domain.Country;
 4import com.demo.project98.domain.Customer;
 5import com.demo.project98.repo.CustomerRepository;
 6import org.springframework.beans.factory.annotation.Autowired;
 7import org.springframework.boot.CommandLineRunner;
 8import org.springframework.boot.SpringApplication;
 9import org.springframework.boot.autoconfigure.SpringBootApplication;
10import org.springframework.cache.Cache;
11import org.springframework.cache.CacheManager;
12import org.springframework.cache.annotation.EnableCaching;
13import org.springframework.context.annotation.Bean;
14
15@SpringBootApplication
16@EnableCaching
17public class Main {
18
19    @Autowired
20    CacheManager cacheManager;
21
22    @Autowired
23    CustomerRepository customerRepository;
24
25    public static void main(String[] args) {
26        SpringApplication.run(Main.class, args);
27    }
28
29    @Bean
30    public CommandLineRunner sendData() {
31        return args -> {
32            Cache cache = cacheManager.getCache("countryCache");
33            cache.put("FR", new Country("FR", "France", "Paris"));
34            cache.put("US", new Country("US", "United State Of America", "Washington DC"));
35            cache.put("IN", new Country("IN", "India", "Delhi"));
36            //Since cache is configure to hold only 2 values, one element is auto evicted!
37
38            for (int i = 0; i < 200; i++) {
39                customerRepository.save(Customer.builder().name("customer_" + i).phone("phone_" + i).build());
40            }
41            System.out.println("Seeded!");
42        };
43    }
44
45}

 1<?xml version="1.0" encoding="UTF-8"?>
 2<config xmlns='http://www.ehcache.org/v3'>
 3    <cache alias="countryCache">
 4        <key-type>java.lang.String</key-type>
 5        <value-type>com.demo.project98.domain.Country</value-type>
 6        <expiry>
 7            <ttl unit="minutes">1</ttl>
 8        </expiry>
 9        <listeners>
10            <listener>
11                <class>com.demo.project98.service.CountryCacheListener</class>
12                <event-firing-mode>ASYNCHRONOUS</event-firing-mode>
13                <event-ordering-mode>ORDERED</event-ordering-mode>
14                <events-to-fire-on>CREATED</events-to-fire-on>
15                <events-to-fire-on>REMOVED</events-to-fire-on>
16                <events-to-fire-on>EXPIRED</events-to-fire-on>
17            </listener>
18        </listeners>
19        <resources>
20            <heap unit="entries">2</heap>
21        </resources>
22        <heap-store-settings>
23            <max-object-graph-size>2</max-object-graph-size>
24            <max-object-size unit="kB">5</max-object-size>
25        </heap-store-settings>
26    </cache>
27</config>

1$java --version
2openjdk 17.0.3 2022-04-19 LTS

1docker run -p 5432:5432 --name pg-container -e POSTGRES_PASSWORD=password -d postgres:9.6.10
2docker ps
3docker exec -it pg-container psql -U postgres -W postgres
4CREATE USER test WITH PASSWORD 'test@123';
5CREATE DATABASE "test-db" WITH OWNER "test" ENCODING UTF8 TEMPLATE template0;
6grant all PRIVILEGES ON DATABASE "test-db" to test;
7
8docker stop pg-container
9docker start pg-container

1./gradlew clean build
2./gradlew bootRun