【spring之条件评估器】

本文主要是介绍【spring之条件评估器】，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

1. ConditionEvaluator是干嘛的

内部的使用类,用来评估注解的

2. 先看其属性类ConditionContextImp context

private static class ConditionContextImpl implements ConditionContext {@Nullableprivate final BeanDefinitionRegistry registry;@Nullableprivate final ConfigurableListableBeanFactory beanFactory;private final Environment environment;private final ResourceLoader resourceLoader;@Nullableprivate final ClassLoader classLoader;// 构造器, 实例化时构造这些参数public ConditionContextImpl(@Nullable BeanDefinitionRegistry registry,@Nullable Environment environment, @Nullable ResourceLoader resourceLoader) {this.registry = registry;this.beanFactory = deduceBeanFactory(registry);this.environment = (environment != null ? environment : deduceEnvironment(registry));this.resourceLoader = (resourceLoader != null ? resourceLoader : deduceResourceLoader(registry));this.classLoader = deduceClassLoader(resourceLoader, this.beanFactory);}@Nullable// 根据子类类型，推到出beanFactory！private ConfigurableListableBeanFactory deduceBeanFactory(@Nullable BeanDefinitionRegistry source) {if (source instanceof ConfigurableListableBeanFactory) {return (ConfigurableListableBeanFactory) source;}if (source instanceof ConfigurableApplicationContext) {return (((ConfigurableApplicationContext) source).getBeanFactory());}return null;}// 获取到环境private Environment deduceEnvironment(@Nullable BeanDefinitionRegistry source) {if (source instanceof EnvironmentCapable) {return ((EnvironmentCapable) source).getEnvironment();}return new StandardEnvironment();}// 推到出资源加载器private ResourceLoader deduceResourceLoader(@Nullable BeanDefinitionRegistry source) {if (source instanceof ResourceLoader) {return (ResourceLoader) source;}// 不是ResouceLoader类型的话，就初始化一个默认资源加载器return new DefaultResourceLoader();}@Nullable// 不解释啦，看不懂就别看了private ClassLoader deduceClassLoader(@Nullable ResourceLoader resourceLoader,@Nullable ConfigurableListableBeanFactory beanFactory) {if (resourceLoader != null) {ClassLoader classLoader = resourceLoader.getClassLoader();if (classLoader != null) {return classLoader;}}if (beanFactory != null) {return beanFactory.getBeanClassLoader();}return ClassUtils.getDefaultClassLoader();}@Override// 获取beanDefinition注册器public BeanDefinitionRegistry getRegistry() {Assert.state(this.registry != null, "No BeanDefinitionRegistry available");return this.registry;}@Override@Nullable// 返回beanFactorypublic ConfigurableListableBeanFactory getBeanFactory() {return this.beanFactory;}@Overridepublic Environment getEnvironment() {return this.environment;}@Overridepublic ResourceLoader getResourceLoader() {return this.resourceLoader;}@Override@Nullablepublic ClassLoader getClassLoader() {return this.classLoader;}
}
// Context information for use by Condition implementations
// 条件实现类使用的上下文信息类
public interface ConditionContext {// 获取BeanDefinition信息BeanDefinitionRegistry getRegistry();// 这不用说获取容器ConfigurableListableBeanFactory getBeanFactory();// 获取环境Environment getEnvironment();// 获取资源加载器ResourceLoader getResourceLoader();// 获取类加载器ClassLoader getClassLoader();
}

3. 看ConditionEvaluator 的内部方法

// 构造器
public ConditionEvaluator(@Nullable BeanDefinitionRegistry registry,@Nullable Environment environment, @Nullable ResourceLoader resourceLoader) {// 根据参数实例化条件上下文this.context = new ConditionContextImpl(registry, environment, resourceLoader);
}// 是否跳过
public boolean shouldSkip(AnnotatedTypeMetadata metadata) {return shouldSkip(metadata, null);
}public boolean shouldSkip(@Nullable AnnotatedTypeMetadata metadata, @Nullable ConfigurationPhase phase) {if (metadata == null || !metadata.isAnnotated(Conditional.class.getName())) {return false;}if (phase == null) {if (metadata instanceof AnnotationMetadata &&ConfigurationClassUtils.isConfigurationCandidate((AnnotationMetadata) metadata)) {return shouldSkip(metadata, ConfigurationPhase.PARSE_CONFIGURATION);}return shouldSkip(metadata, ConfigurationPhase.REGISTER_BEAN);}List<Condition> conditions = new ArrayList<>();for (String[] conditionClasses : getConditionClasses(metadata)) {for (String conditionClass : conditionClasses) {Condition condition = getCondition(conditionClass, this.context.getClassLoader());conditions.add(condition);}}AnnotationAwareOrderComparator.sort(conditions);for (Condition condition : conditions) {ConfigurationPhase requiredPhase = null;if (condition instanceof ConfigurationCondition) {requiredPhase = ((ConfigurationCondition) condition).getConfigurationPhase();}if ((requiredPhase == null || requiredPhase == phase) && !condition.matches(this.context, metadata)) {return true;}}return false;
}

4. AnnotationTypeMetadata 是干嘛的

// 用于获取元素上的注解的元数据，不用看了！
MergedAnnotations getAnnotations();default boolean isAnnotated(String annotationName) {return getAnnotations().isPresent(annotationName);
}default Map<String, Object> getAnnotationAttributes(String annotationName) {return getAnnotationAttributes(annotationName, false);
}default Map<String, Object> getAnnotationAttributes(String annotationName,boolean classValuesAsString) {MergedAnnotation<Annotation> annotation = getAnnotations().get(annotationName,null, MergedAnnotationSelectors.firstDirectlyDeclared());if (!annotation.isPresent()) {return null;}return annotation.asAnnotationAttributes(Adapt.values(classValuesAsString, true));
}default MultiValueMap<String, Object> getAllAnnotationAttributes(String annotationName) {return getAllAnnotationAttributes(annotationName, false);
}default MultiValueMap<String, Object> getAllAnnotationAttributes(String annotationName, boolean classValuesAsString) {Adapt[] adaptations = Adapt.values(classValuesAsString, true);return getAnnotations().stream(annotationName).filter(MergedAnnotationPredicates.unique(MergedAnnotation::getMetaTypes)).map(MergedAnnotation::withNonMergedAttributes).collect(MergedAnnotationCollectors.toMultiValueMap(map ->map.isEmpty() ? null : map, adaptations));
}

5. Condition 接口

boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata);

这篇关于【spring之条件评估器】的文章就介绍到这儿，希望我们推荐的文章对编程师们有所帮助！

---