从自动配置创建Autowireable@beans

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• 通过spring配置来配置bean的数量；
• 通过@configurationproperties获取此配置；
• 从自动配置模块根据所述配置创建并注入@beans；
• 能够@autowire在应用程序中创建bean。

示例：使通过spring配置声明基于咖啡因的缓存@beans的数量成为可能。以下是基于类似问题的公认答案的实现：

首先，引导自动配置模块：

@Component
@ConfigurationProperties
@Data
public class Props {

    private LocalCacheConf cache = new LocalCacheConf();

    @Data
    public static class LocalCacheConf {

        /**
        * List of caches to create, with accompanying configuration.
        */
        private List<CacheDef> caches = new ArrayList<>();

        @Data
        public static class CacheDef {

            private String name;
            private CaffeineCacheConf properties;
        }

        @Data
        public static class CaffeineCacheConf {

            private long maximumSize = -1;
        }
    }
}


@Configuration
@Slf4j
public class LocalCacheConfig implements BeanFactoryAware {

    @Autowired private Props props;
    @Setter private BeanFactory beanFactory;
    private CaffeineCacheManager localCacheManager;

    @PostConstruct
    public void configure() {
        setCacheManager();
        createCaches( props.getCache() );
    }

    private void createCaches( LocalCacheConf locCacheConf ) {
        ConfigurableBeanFactory configurableBeanFactory = (ConfigurableBeanFactory) beanFactory;

        for ( CacheDef cacheProps : locCacheConf.getCaches() ) {
            Cache cache = createAndConfigureCache(
                    cacheProps.getName(),
                    cacheProps.getProperties()
            );
            configurableBeanFactory.registerSingleton( cacheProps.getName(), cache );
        }
    }

    private Cache createAndConfigureCache( String name, CaffeineCacheConf props ) {
        Caffeine<Object, Object> c = Caffeine.newBuilder().recordStats();

        if ( props.getMaximumSize() >= 0 ) {
            c.maximumSize( props.getMaximumSize() );
        }
        // can extend config to include additional properties

        localCacheManager.setCaffeine( c );
        log.info( "building [{}] cache with config: [{}]", name, c.toString() );

        return localCacheManager.getCache( name );
    }

    private void setCacheManager() {
        log.info( "creating {}...", "localCacheManager" );
        localCacheManager = new CaffeineCacheManager();
        ( (ConfigurableBeanFactory) beanFactory )
                .registerSingleton( "localCacheManager", localCacheManager );
    }
}

cache:
  caches:
    - name: c1
      properties:
        maximumSize: 50
    - name: c2
      properties:
        maximumSize: 5000

Answer 1

如果这是一个Spring Boot项目，请查看：

https://docs.spring.io/spring-boot/docs/current-snapshot/reference/html/boot-features-caching.html#boot-features-caching-provider-caffeine