中大型应用开发中,缓存的重要性不言而喻,早期常用的进程式类的缓存,像 EhCache 或者是 ConcurrentHashMap 这样的容器,发展到如今,更流行的是那些分布式的独立缓存服务,如:Redis、Memcached。

对于 Java 应用开发者来说,Spring 提供了完善的缓存抽象机制,结合 Spring Boot 的使用,可以做到非常轻松的完成缓存实现和切换。下面通过简单的示例,展示下如何快速为你的 Spring Boot 应用添加 Redis Caching。

  1. 相关依赖
<dependencies>
<!-- 添加该依赖后,将自动使用 Redis 作为 Cache Provider -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-redis</artifactId>
</dependency>

<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<scope>runtime</scope>
</dependency>

<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<optional>true</optional>
</dependency>
</dependencies>
  1. 补充配置
spring:
datasource:
url: jdbc:mysql://localhost:3306/test?useUnicode=true&zeroDateTimeBehavior=convertToNull&characterEncoding=utf-8&useSSL=false&serverTimezone=GMT%2B8&tinyInt1isBit=false
username: root
password: root
jpa:
database-platform: org.hibernate.dialect.MySQL5InnoDBDialect
hibernate:
ddl-auto: create
# 开启 SQL 输出,方便查看结果是否走了缓存
show-sql: true
open-in-view: false
redis:
host: localhost
cache:
# 非必须,但如果配置了需补充相应的依赖,否则会出错
#type: redis
redis:
# 过期时间5秒,默认单位:毫秒,等同于设置成 5s、5S
time-to-live: 5000
key-prefix: cn.mariojd.cache.
cache-null-values: false
  1. 添加实体,实现 Serializable 接口
@Data
@Entity
@Builder
@NoArgsConstructor
@AllArgsConstructor
public class User implements Serializable {

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer id;

private String name;

}

定义 Repository 接口:

public interface UserRepository extends JpaRepository<User, Integer> {
}
  1. 编写 Service,进行缓存规则配置,核心注解有:@CacheConfig@Cacheable(缓存新增)、@CachePut(缓存更新)、@CacheEvict(缓存删除)
@Slf4j
@Service
@CacheConfig(cacheNames = "user")
public class UserService {

@Resource
private UserRepository userRepository;

/**
* Key name: key-prefix.classSimpleName.methodName?pn=xxx&ps=xxx&sort=xxx
*/
@Cacheable(key = "#root.targetClass.simpleName+'.'+#root.methodName+'?pn='+#pageable.pageNumber+'&ps='+#pageable.pageSize+'&sort='+#pageable.sort.toString()")
public Page<User> page(Pageable pageable) {
return userRepository.findAll(pageable);
}

@Cacheable(key = "'user.'+#userId", unless = "#result == null")
public Optional<User> get(int userId) {
return userRepository.findById(userId);
}

@Transactional
public User add(String name) {
User user = User.builder().name(name).build();
return userRepository.save(user);
}

@CachePut(key = "'user.'+#userId", unless = "#result == null")
@Transactional
public Optional<User> update(int userId, String name) {
Optional<User> userOptional = userRepository.findById(userId);
userOptional.ifPresent(user -> {
user.setName(name);
userRepository.save(user);
});
return userOptional;
}

@CacheEvict(key = "'user.'+#userId")
@Transactional
public void delete(int userId) {
userRepository.findById(userId).ifPresent(user -> userRepository.delete(user));
}

}
  1. 缓存测试,为启动类添加:@EnableCaching
@Slf4j
@EnableCaching
@SpringBootApplication
public class SpringBootCacheApplication implements ApplicationRunner {

public static void main(String[] args) {
new SpringApplicationBuilder()
.sources(SpringBootCacheApplication.class)
.bannerMode(Banner.Mode.OFF)
.web(WebApplicationType.NONE)
.run(args);
}

@Resource
private UserRepository userRepository;

@PostConstruct
public void init() {
// 初始化数据
for (int i = 0; i < 10; i++) {
User user = User.builder().name("ZS" + i).build();
userRepository.save(user);
}
}

@Resource
private UserService userService;

@Resource
private Environment environment;

@Override
public void run(ApplicationArguments args) throws InterruptedException {
// 测试缓存,观察是否有SQL输出

PageRequest pageable = PageRequest.of(0, 5);
userService.page(pageable);
for (int i = 0; i < 5; i++) {
userService.page(pageable);
log.info("Reading page cache...");
}
// 由于配置是5秒中后缓存失效,这里休眠后重新读取
TimeUnit.MILLISECONDS.sleep(Integer.parseInt(environment.getProperty("spring.cache.redis.time-to-live", "5000")));
log.warn("Page Cache expired : " + userService.page(pageable).getTotalElements());

log.info("\n");

// Test CRUD Cache![enter description here](http://image.mariojd.cn/happyjared/201949/20190409101855.png)
User user = userService.add("李四");
int userId = user.getId();
userService.get(userId);
log.info("Reading user cache..." + userService.get(userId));

userService.update(userId, "王五");
log.info("Reading new user cache..." + userService.get(userId));

userService.delete(userId);
log.warn("User Cache delete : " + userService.get(userId));
}

}

从图中的红框部分输出可以看到,这些查询走了缓存,如果需要在 redis 中查看缓存内容,可以将配置中的 TTL 时间调大:

测试输出

扩展操作

Spring 允许开发者们通过自定义 KeyGenerator 来覆盖繁琐的 Key 定义(非必须),同时也允许我们配置自定义的 CacheManager,下面来看看如何编写 KeyGenerator:

@CacheConfig

@Slf4j
public class CustomKeyGenerator implements KeyGenerator {

@Override
public Object generate(Object target, Method method, Object... params) {
// 类名.方法名.参数值
String keySuffix = target.getClass().getSimpleName() + "." + method.getName() + "." + Arrays.toString(params);
log.info("Cache key suffix : {}", keySuffix);
return keySuffix;
}

}

接着配置注册为 Bean:

@Configuration
public class CustomConfig {

@Bean
public CustomKeyGenerator customKeyGenerator() {
return new CustomKeyGenerator();
}

}

编写 Service 用于测试,具体的测试代码这里就不再贴出来了,有兴趣的可以自行尝试。

@Slf4j
@Service
@CacheConfig(cacheNames = "user")
public class UserSupportService {

@Resource
private UserRepository userRepository;

/**
* 使用了自定义的KeyGenerator
* 缓存生效需满足:存在不为空的入参i、且返回值非空
*/
@Cacheable(keyGenerator = "customKeyGenerator", condition = "#i!=null", unless = "#result.isEmpty()")
public List<User> list(Integer i) {
return userRepository.findAll();
}

}

参考阅读

Spring-Boot-Caching

示例源码
欢迎关注我的个人公众号:超级码里奥
如果这对您有帮助,欢迎点赞和分享,转载请注明出处

最后更新: 2019年04月10日 16:13

原始链接: https://blog.mariojd.cn/spring-boot-caching-example.html

× 支持创作
打赏二维码