自动配置实践

• 例如打开aop相关类
  

• 查看源码

// 表示这是1个配置类
@Configuration(proxyBeanMethods = false)
// 表示配置文件中有spring.aop的配置，且值为true，下面的组件才生效，matchIfMissing = true表示始终默认生效
@ConditionalOnProperty(prefix = "spring.aop", name = "auto", havingValue = "true", matchIfMissing = true)
public class AopAutoConfiguration {

	@Configuration(proxyBeanMethods = false)
// 表示只有导入了Advice类的时候，该组件才生效
	@ConditionalOnClass(Advice.class)
	static class AspectJAutoProxyingConfiguration {

		@Configuration(proxyBeanMethods = false)
		@EnableAspectJAutoProxy(proxyTargetClass = false)
		@ConditionalOnProperty(prefix = "spring.aop", name = "proxy-target-class", havingValue = "false",
				matchIfMissing = false)
		static class JdkDynamicAutoProxyConfiguration {

		}

		@Configuration(proxyBeanMethods = false)
		@EnableAspectJAutoProxy(proxyTargetClass = true)
		@ConditionalOnProperty(prefix = "spring.aop", name = "proxy-target-class", havingValue = "true",
				matchIfMissing = true)
		static class CglibAutoProxyConfiguration {

		}

	}

// 表示这是1个配置类
	@Configuration(proxyBeanMethods = false)
// 表示如果容器中没有Advice类时，如下组件生效
	@ConditionalOnMissingClass("org.aspectj.weaver.Advice")
// 表示配置文件中有spring.aop的配置，且为proxy-target-class时，当前组件生效，matchIfMissing = true表示始终默认开启
// 也就是说当前方法表示，没有导入aop相关依赖时，开启1个简易版的aop
	@ConditionalOnProperty(prefix = "spring.aop", name = "proxy-target-class", havingValue = "true",
			matchIfMissing = true)
	static class ClassProxyingConfiguration {

		ClassProxyingConfiguration(BeanFactory beanFactory) {
			if (beanFactory instanceof BeanDefinitionRegistry) {
				BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
				AopConfigUtils.registerAutoProxyCreatorIfNecessary(registry);
				AopConfigUtils.forceAutoProxyCreatorToUseClassProxying(registry);
			}
		}

	}

}

• 查看CacheAutoConfiguration
  

@Configuration(proxyBeanMethods = false)
// 判断容器中是否有该类
@ConditionalOnClass(CacheManager.class)
// 判断容器中是否有该组件
@ConditionalOnBean(CacheAspectSupport.class)
@ConditionalOnMissingBean(value = CacheManager.class, name = "cacheResolver")
@EnableConfigurationProperties(CacheProperties.class)
@AutoConfigureAfter({ CouchbaseDataAutoConfiguration.class, HazelcastAutoConfiguration.class,
		HibernateJpaAutoConfiguration.class, RedisAutoConfiguration.class })
@Import({ CacheConfigurationImportSelector.class, CacheManagerEntityManagerFactoryDependsOnPostProcessor.class })
public class CacheAutoConfiguration {

	@Bean
	@ConditionalOnMissingBean
	public CacheManagerCustomizers cacheManagerCustomizers(ObjectProvider<CacheManagerCustomizer<?>> customizers) {
		return new CacheManagerCustomizers(customizers.orderedStream().collect(Collectors.toList()));
	}

	@Bean
	public CacheManagerValidator cacheAutoConfigurationValidator(CacheProperties cacheProperties,
			ObjectProvider<CacheManager> cacheManager) {
		return new CacheManagerValidator(cacheProperties, cacheManager);
	}

	@ConditionalOnClass(LocalContainerEntityManagerFactoryBean.class)
	@ConditionalOnBean(AbstractEntityManagerFactoryBean.class)
	static class CacheManagerEntityManagerFactoryDependsOnPostProcessor
			extends EntityManagerFactoryDependsOnPostProcessor {

		CacheManagerEntityManagerFactoryDependsOnPostProcessor() {
			super("cacheManager");
		}

	}

	/**
	 * Bean used to validate that a CacheManager exists and provide a more meaningful
	 * exception.
	 */
	static class CacheManagerValidator implements InitializingBean {

		private final CacheProperties cacheProperties;

		private final ObjectProvider<CacheManager> cacheManager;

		CacheManagerValidator(CacheProperties cacheProperties, ObjectProvider<CacheManager> cacheManager) {
			this.cacheProperties = cacheProperties;
			this.cacheManager = cacheManager;
		}

		@Override
		public void afterPropertiesSet() {
			Assert.notNull(this.cacheManager.getIfAvailable(),
					() -> "No cache manager could be auto-configured, check your configuration (caching type is '"
							+ this.cacheProperties.getType() + "')");
		}

	}

	/**
	 * {@link ImportSelector} to add {@link CacheType} configuration classes.
	 */
	static class CacheConfigurationImportSelector implements ImportSelector {

		@Override
		public String[] selectImports(AnnotationMetadata importingClassMetadata) {
			CacheType[] types = CacheType.values();
			String[] imports = new String[types.length];
			for (int i = 0; i < types.length; i++) {
				imports[i] = CacheConfigurations.getConfigurationClass(types[i]);
			}
			return imports;
		}

	}

}