public User getUser(long userId) {
    // 從緩存查詢
    User user = cache.get(userId);
    if (user != null) {
        return user;
    }
    // 從數(shù)據(jù)庫加載
    User dbUser = loadDataFromDB(userId);
    if (dbUser != null) {
        // 設(shè)置到緩存中
        cache.put(userId, dbUser)
    }
    return dbUser;
}

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-cache</artifactId>
</dependency>
<dependency>
    <groupId>com.github.ben-manes.caffeine</groupId>
    <artifactId>caffeine</artifactId>
</dependency>

@Slf4j
@EnableCaching
@Configuration
public class CacheConfig {
    @Autowired
    @Qualifier("cacheExecutor")
    private Executor cacheExecutor;
    @Bean
    public Caffeine<Object, Object> caffeineCache() {
        return Caffeine.newBuilder()
                // 設(shè)置最后一次寫入或訪問后經(jīng)過固定時(shí)間過期
                .expireAfterAccess(7, TimeUnit.DAYS)
                // 初始的緩存空間大小
                .initialCapacity(500)
                // 使用自定義線程池
                .executor(cacheExecutor)
                .removalListener(((key, value, cause) -> log.info("key:{} removed, removalCause:{}.", key, cause.name())))
                // 緩存的最大條數(shù)
                .maximumSize(1000);
    }
    @Bean
    public CacheManager cacheManager() {
        CaffeineCacheManager caffeineCacheManager = new CaffeineCacheManager();
        caffeineCacheManager.setCaffeine(caffeineCache());
        // 不緩存空值
        caffeineCacheManager.setAllowNullValues(false);
        return caffeineCacheManager;
    }
}

@Slf4j
@Service
public class AddressService {
    public static final String CACHE_NAME = "caffeine:address";
    private static final AtomicLong ID_CREATOR = new AtomicLong(0);
    private Map<Long, AddressDTO> addressMap;
    public AddressService() {
        addressMap = new ConcurrentHashMap<>();
        addressMap.put(ID_CREATOR.incrementAndGet(), AddressDTO.builder().customerId(ID_CREATOR.get()).address("地址1").build());
        addressMap.put(ID_CREATOR.incrementAndGet(), AddressDTO.builder().customerId(ID_CREATOR.get()).address("地址2").build());
        addressMap.put(ID_CREATOR.incrementAndGet(), AddressDTO.builder().customerId(ID_CREATOR.get()).address("地址3").build());
    }
    @Cacheable(cacheNames = {CACHE_NAME}, key = "#customerId")
    public AddressDTO getAddress(long customerId) {
        log.info("customerId：{} 沒有走緩存，開始從數(shù)據(jù)庫查詢", customerId);
        return addressMap.get(customerId);
    }
    @CachePut(cacheNames = {CACHE_NAME}, key = "#result.customerId")
    public AddressDTO create(String address) {
        long customerId = ID_CREATOR.incrementAndGet();
        AddressDTO addressDTO = AddressDTO.builder().customerId(customerId).address(address).build();
        addressMap.put(customerId, addressDTO);
        return addressDTO;
    }
    @CachePut(cacheNames = {CACHE_NAME}, key = "#result.customerId")
    public AddressDTO update(Long customerId, String address) {
        AddressDTO addressDTO = addressMap.get(customerId);
        if (addressDTO == null) {
            throw new RuntimeException("沒有 customerId = " + customerId + "的地址");
        }
        addressDTO.setAddress(address);
        return addressDTO;
    }
    @CacheEvict(cacheNames = {CACHE_NAME}, key = "#customerId")
    public boolean delete(long customerId) {
        log.info("緩存 {} 被刪除", customerId);
        return true;
    }
}

@RunWith(SpringRunner.class)
@SpringBootTest(classes = CaffeineApplication.class)
@Slf4j
public class CaffeineApplicationTests {
    @Autowired
    private AddressService addressService;
    @Autowired
    private CacheManager cacheManager;
    @Test
    public void testCache() {
        // 插入緩存 和數(shù)據(jù)庫
        AddressDTO newInsert = addressService.create("南山大道");
        // 要走緩存
        AddressDTO address = addressService.getAddress(newInsert.getCustomerId());
        long customerId = 2;
        // 第一次未命中緩存，打印 customerId：{} 沒有走緩存，開始從數(shù)據(jù)庫查詢
        AddressDTO address2 = addressService.getAddress(customerId);
        // 命中緩存
        AddressDTO cacheAddress2 = addressService.getAddress(customerId);
        // 更新數(shù)據(jù)庫和緩存
        addressService.update(customerId, "地址 2 被修改");
        // 更新后查詢，依然命中緩存
        AddressDTO hitCache2 = addressService.getAddress(customerId);
        Assert.assertEquals(hitCache2.getAddress(), "地址 2 被修改");
        // 刪除緩存
        addressService.delete(customerId);
        // 未命中緩存, 從數(shù)據(jù)庫讀取
        AddressDTO hit = addressService.getAddress(customerId);
        System.out.println(hit.getCustomerId());
    }
}