这几天在开发的项目中，考虑引入一些缓存机制。顺便又了解了一下spring-boot的缓存、以及JSR107、ehcache。并做了一些使用实例。

spring-boot缓存使用实例

spring-boot中引入依赖spring-boot-starter-cache，pom.xml:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-cache</artifactId>
</dependency>

/**
 * 启动类
 */
@SpringBootApplication
@EnableAutoConfiguration
@EnableCaching // 启用缓存
public class Application extends SpringBootServletInitializer {

    @Override
    protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
        return application.sources(Application.class);
    }

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

/**
 * restful类
 */
@RestController
public class SampleController {
    @Autowired
    private SampleServiceImpl sampleService;

    @RequestMapping("/sample/test")
    public BaseQueryParam test(BaseQueryParam dto) {
        return sampleService.testCache(dto);
    }

}

@Service
public class SampleServiceImpl {

    // 取第一个参数可以用这几种姿势#root.args[1]或#p0或#a0
    @Cacheable(value="SampleServiceImpl", key="#p0.resourceId")
    public BaseQueryParam testCache(BaseQueryParam param) {
        System.out.println("第1次访问时未缓存，打印此文本");
        return param;
    }

}

public class BaseQueryParam {
    /**
     * 资源标识。主要用来标识需要访问的资源类型
     */
    private String resourceId;

    public String getResourceId() {
        return resourceId;
    }

    public void setResourceId(String resourceId) {
        this.resourceId = resourceId;
    }

}

测试：

http://localhost:8080/sample/test?resourceId=abc

访问的时候当传入的参数resourceId一样时，第1次控制台打印“第1次访问时未缓存，打印此文本”，后面就没有打印。

生命周期：如果没检测到EhCache3,Hazelcast,Infinispan等类型，将会使用Simple类型，即使用ConcurrentHashMap进行缓存，这种类型的缓存是永久有效的。具体的使用可以参考org.springframework.cache.concurrent.ConcurrentMapCacheManager；

使用JSR107和ehcache

JSR107的注解为@CacheResult，springboot建议不要和@Cacheable混合使用。同时改为使用ehcache来配置缓存，可以有效的管理内存的占用、缓存的生命周期等。

spring-boot中引入依赖spring-boot-starter-cache，pom.xml中增加:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-cache</artifactId>
</dependency>
<dependency>
    <groupId>org.ehcache</groupId>
    <artifactId>ehcache</artifactId>
    <version>3.2.1</version>
</dependency>
<dependency>
    <groupId>javax.cache</groupId>
    <artifactId>cache-api</artifactId>
</dependency>

/**
 * 启动类
 */
@SpringBootApplication
@EnableAutoConfiguration
@EnableCaching // 启用缓存
public class Application extends SpringBootServletInitializer {

    @Override
    protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
        return application.sources(Application.class);
    }

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

/**
 * restful类
 */
@RestController
public class SampleController {
    @Autowired
    private SampleServiceImpl sampleService;

    @RequestMapping("/sample/test")
    public BaseQueryParam test(BaseQueryParam dto) {
        return sampleService.testCache(dto);
    }

}

@Service
public class SampleServiceImpl {

    // JSR107的注解为@CacheResult，springboot建议不要和@Cacheable混合使用
    @CacheResult(cacheName = "SampleServiceImpl", cacheKeyGenerator = SampleCacheKeyGenerator.class)
    public BaseQueryParam testCache(BaseQueryParam param) {
        System.out.println("第1次访问时未缓存，打印此文本");
        return param;
    }

    /**
     * 用于生成key的类
     */
    public static class SampleCacheKeyGenerator implements CacheKeyGenerator {

        @Override
        public GeneratedCacheKey generateCacheKey(CacheKeyInvocationContext<? extends Annotation> arg0) {
            BaseQueryParam param = (BaseQueryParam) (arg0.getAllParameters()[0].getValue());
            if (null == param) {
                return null;
            }
            return new SampleGeneratedCacheKey(param.getResourceId());
        }

    }

    /**
     * 缓存key类
     */
    public static class SampleGeneratedCacheKey implements GeneratedCacheKey {
        private static final long serialVersionUID = 1L;
        private final String key;

        public SampleGeneratedCacheKey(String key) {
            this.key = key;
        }

        @Override
        public int hashCode() {
            final int prime = 31;
            int result = 1;
            result = prime * result + ((key == null) ? 0 : key.hashCode());
            return result;
        }

        @Override
        public boolean equals(Object obj) {
            if (this == obj)
                return true;
            if (obj == null)
                return false;
            if (getClass() != obj.getClass())
                return false;
            SampleGeneratedCacheKey other = (SampleGeneratedCacheKey) obj;
            if (key == null) {
                if (other.key != null)
                    return false;
            } else if (!key.equals(other.key))
                return false;
            return true;
        }

    }

}

public class BaseQueryParam implements Serializable { // ehcache缓存必须要实现Serializable接口
    /**
     * 资源标识。主要用来标识需要访问的资源类型
     */
    private String resourceId;

    public String getResourceId() {
        return resourceId;
    }

    public void setResourceId(String resourceId) {
        this.resourceId = resourceId;
    }

}

application.properties配置：

# SampleServiceImpl 对应cacheName = "SampleServiceImpl"
spring.cache.cache-names=SampleServiceImpl
spring.cache.ehcache.config=calsspath:ehcache.xml

关于JSR107

https://jcp.org/en/jsr/detail?id=107

描述（网上抄来的）：JCache规范定义了一种对Java对象临时在内存中进行缓存的方法，包括对象的创建、共享访问、假脱机（spooling）、失效、各JVM的一致性等，可被用于缓存JSP内最经常读取的数据，如产品目录和价格列表。利用JCACHE，多数查询的反应时间会因为有缓存的数据而加快（内部测试表明反应时间大约快15倍）。