Spring5源码解析5-ConfigurationClassPostProces…

2019-10-16 08:19:57来源:博客园 阅读 ()

新老客户大回馈,云服务器低至5折

Spring5源码解析5-ConfigurationClassPostProcessor (上)

接上回,我们讲到了refresh()方法中的invokeBeanFactoryPostProcessors(beanFactory)方法主要在执行BeanFactoryPostProcessor和其子接口BeanDefinitionRegistryPostProcessor的方法。

在创建AnnotationConfigApplicationContext对象时Spring就添加了一个非常重要的BeanFactoryPostProcessor接口实现类:ConfigurationClassPostProcessor。注意,这里说的添加只是添加到容器的beanDefinitionMap中,还没有创建真正的实例Bean。

简单回顾一下ConfigurationClassPostProcessor是在什么时候被添加到容器中的:在AnnotationConfigApplicationContext的无参构造器中创建AnnotatedBeanDefinitionReader对象时会向传入的BeanDefinitionRegistry中注册解析注解配置类相关的processors的BeanDefinitionConfigurationClassPostProcessor就是在此处被添加到容器中的。


ConfigurationClassPostProcessor

先看一些ConfigurationClassPostProcessor的继承体系:

ConfigurationClassPostProcessor

ConfigurationClassPostProcessor实现了BeanDefinitionRegistryPostProcessor接口,也就拥有了在Spring容器启动时,往容器中注册BeanDefinition的能力。

我们知道,ConfigurationClassPostProcessor#postProcessBeanDefinitionRegistry方法是在refresh();方法中的invokeBeanFactoryPostProcessors(beanFactory);中被执行的,下面我们就一起来看一下该方法。

ConfigurationClassPostProcessor#postProcessBeanDefinitionRegistry

@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) {
    int registryId = System.identityHashCode(registry);
    if (this.registriesPostProcessed.contains(registryId)) {
        throw new IllegalStateException(
                "postProcessBeanDefinitionRegistry already called on this post-processor against " + registry);
    }
    if (this.factoriesPostProcessed.contains(registryId)) {
        throw new IllegalStateException(
                "postProcessBeanFactory already called on this post-processor against " + registry);
    }
    this.registriesPostProcessed.add(registryId);

    processConfigBeanDefinitions(registry);
}

主要的逻辑在processConfigBeanDefinitions(registry);中,点开源码:

public void processConfigBeanDefinitions(BeanDefinitionRegistry registry) {
    List<BeanDefinitionHolder> configCandidates = new ArrayList<>();
    //获取所有的BeanDefinitionName
    String[] candidateNames = registry.getBeanDefinitionNames();

    for (String beanName : candidateNames) {
        BeanDefinition beanDef = registry.getBeanDefinition(beanName);

        // https://docs.spring.io/spring/docs/5.1.8.RELEASE/spring-framework-reference/core.html#beans-java-basic-concepts
        // Full @Configuration vs “lite” @Bean mode
        if (ConfigurationClassUtils.isFullConfigurationClass(beanDef) ||
                ConfigurationClassUtils.isLiteConfigurationClass(beanDef)) {
            if (logger.isDebugEnabled()) {
                logger.debug("Bean definition has already been processed as a configuration class: " + beanDef);
            }
        }

        // 校验是否为配置类
        // 配置类分为两种 Full @Configuration vs “lite” @Bean mode
        // 校验之后在 BeanDefinition 中添加标志属性
        // 如果满足条件则加入到configCandidates
        else if (ConfigurationClassUtils.checkConfigurationClassCandidate(beanDef, this.metadataReaderFactory)) {
            // 如果是配置类,就放到 configCandidates 变量中
            configCandidates.add(new BeanDefinitionHolder(beanDef, beanName));
        }
    }

    // Return immediately if no @Configuration classes were found
    if (configCandidates.isEmpty()) {
        return;
    }

    // Sort by previously determined @Order value, if applicable
    configCandidates.sort((bd1, bd2) -> {
        int i1 = ConfigurationClassUtils.getOrder(bd1.getBeanDefinition());
        int i2 = ConfigurationClassUtils.getOrder(bd2.getBeanDefinition());
        return Integer.compare(i1, i2);
    });

    // Detect any custom bean name generation strategy supplied through the enclosing application context
    SingletonBeanRegistry sbr = null;
    // 传入的 registry 是 DefaultListableBeanFactory
    if (registry instanceof SingletonBeanRegistry) {
        sbr = (SingletonBeanRegistry) registry;
        if (!this.localBeanNameGeneratorSet) {
            //获取自定义BeanNameGenerator,一般情况下为空
            BeanNameGenerator generator = (BeanNameGenerator) sbr.getSingleton(CONFIGURATION_BEAN_NAME_GENERATOR);
            if (generator != null) {
                this.componentScanBeanNameGenerator = generator;
                this.importBeanNameGenerator = generator;
            }
        }
    }

    if (this.environment == null) {
        this.environment = new StandardEnvironment();
    }

    // Parse each @Configuration class
    // new ConfigurationClassParser,用来解析 @Configuration 类
    ConfigurationClassParser parser = new ConfigurationClassParser(
            this.metadataReaderFactory, this.problemReporter, this.environment,
            this.resourceLoader, this.componentScanBeanNameGenerator, registry);

    // 将 configCandidates 转成 set  candidates , 去重
    Set<BeanDefinitionHolder> candidates = new LinkedHashSet<>(configCandidates);
    Set<ConfigurationClass> alreadyParsed = new HashSet<>(configCandidates.size());
    do {
        // 解析配置类
        parser.parse(candidates);
        parser.validate();

        Set<ConfigurationClass> configClasses = new LinkedHashSet<>(parser.getConfigurationClasses());
        configClasses.removeAll(alreadyParsed);

        // Read the model and create bean definitions based on its content
        if (this.reader == null) {
            this.reader = new ConfigurationClassBeanDefinitionReader(
                    registry, this.sourceExtractor, this.resourceLoader, this.environment,
                    this.importBeanNameGenerator, parser.getImportRegistry());
        }
        // Import类,@Bean,@ImportResource 转化为 BeanDefinition
        this.reader.loadBeanDefinitions(configClasses);
        alreadyParsed.addAll(configClasses);

        candidates.clear();
        // 再获取一下容器中BeanDefinition的数据,如果发现数量增加了,说明有新的BeanDefinition被注册了
        if (registry.getBeanDefinitionCount() > candidateNames.length) {
            String[] newCandidateNames = registry.getBeanDefinitionNames();
            Set<String> oldCandidateNames = new HashSet<>(Arrays.asList(candidateNames));
            Set<String> alreadyParsedClasses = new HashSet<>();
            for (ConfigurationClass configurationClass : alreadyParsed) {
                alreadyParsedClasses.add(configurationClass.getMetadata().getClassName());
            }
            for (String candidateName : newCandidateNames) {
                if (!oldCandidateNames.contains(candidateName)) {
                    BeanDefinition bd = registry.getBeanDefinition(candidateName);
                    if (ConfigurationClassUtils.checkConfigurationClassCandidate(bd, this.metadataReaderFactory) &&
                            !alreadyParsedClasses.contains(bd.getBeanClassName())) {
                        candidates.add(new BeanDefinitionHolder(bd, candidateName));
                    }
                }
            }
            candidateNames = newCandidateNames;
        }
    }
    while (!candidates.isEmpty());

    // Register the ImportRegistry as a bean in order to support ImportAware @Configuration classes
    if (sbr != null && !sbr.containsSingleton(IMPORT_REGISTRY_BEAN_NAME)) {
        sbr.registerSingleton(IMPORT_REGISTRY_BEAN_NAME, parser.getImportRegistry());
    }

    if (this.metadataReaderFactory instanceof CachingMetadataReaderFactory) {
        // Clear cache in externally provided MetadataReaderFactory; this is a no-op
        // for a shared cache since it'll be cleared by the ApplicationContext.
        ((CachingMetadataReaderFactory) this.metadataReaderFactory).clearCache();
    }
}

获取所有的BeanDefinitionNames,然后循环这个数组,判断其是否为配置类。

candidateNames

前5个是Spring注册的内置processor,最后一个是传入给AnnotationConfigApplicationContext的配置类AppConfig.class

在Spring中存在两种ConfigurationClass,一种是FullConfigurationClass另一种是LiteConfigurationClass。关于这两者的区别,可以参看笔者文章之前关于Full @Configuration 和 lite @Bean mode的文章。

ConfigurationClassUtils#checkConfigurationClassCandidate方法内部就是在判断属于哪种配置类,并在BeanDefinition中标记判断结果。其具体的判断逻辑如下:

public static boolean isFullConfigurationCandidate(AnnotationMetadata metadata) {
    return metadata.isAnnotated(Configuration.class.getName());
}
private static final Set<String> candidateIndicators = new HashSet<>(8);

static {
    candidateIndicators.add(Component.class.getName());
    candidateIndicators.add(ComponentScan.class.getName());
    candidateIndicators.add(Import.class.getName());
    candidateIndicators.add(ImportResource.class.getName());
}

public static boolean isLiteConfigurationCandidate(AnnotationMetadata metadata) {
    // Do not consider an interface or an annotation...
    if (metadata.isInterface()) {
        return false;
    }

    // Any of the typical annotations found?
    for (String indicator : candidateIndicators) {
        if (metadata.isAnnotated(indicator)) {
            return true;
        }
    }

    // Finally, let's look for @Bean methods...
    try {
        return metadata.hasAnnotatedMethods(Bean.class.getName());
    } catch (Throwable ex) {
        if (logger.isDebugEnabled()) {
            logger.debug("Failed to introspect @Bean methods on class [" + metadata.getClassName() + "]: " + ex);
        }
        return false;
    }
}

判断configCandidates变量中存放的

配置类是否为空,如果不为空,则对其进行排序。

configCandidates

创建ConfigurationClassParser对象,用于解析@Configuration类,完成包的扫描、BeanDefinition的注册。主要通过执行parser.parse(candidates);方法来完成。

执行parser.parse(candidates)方法前 :

执行parser.parse(candidates)方法前

执行parser.parse(candidates)方法后 :

执行parser.parse(candidates)方法后

解析完配置类之后,紧接着又执行了this.reader.loadBeanDefinitions(configClasses);方法。这个方法主要是用来处理Import类@Bean@ImportResource注解。关于这两个方法的具体细节,我们下次再讲。

最后又加了入了对ImportAware接口支持所需要的Bean。

// Register the ImportRegistry as a bean in order to support ImportAware @Configuration classes
if (sbr != null && !sbr.containsSingleton(IMPORT_REGISTRY_BEAN_NAME)) {
    sbr.registerSingleton(IMPORT_REGISTRY_BEAN_NAME, parser.getImportRegistry());
}

关于对ImportAware接口的使用,我们也下次再讲。


未完待续......

源码学习笔记:https://github.com/shenjianeng/spring-code-study

欢迎各位关注公众号,大家一起学习成长。
Coder小黑


原文链接:https://www.cnblogs.com/coderxiaohei/p/11685144.html
如有疑问请与原作者联系

标签:

版权申明:本站文章部分自网络,如有侵权,请联系:west999com@outlook.com
特别注意:本站所有转载文章言论不代表本站观点,本站所提供的摄影照片,插画,设计作品,如需使用,请与原作者联系,版权归原作者所有

上一篇:mybatis 处理枚举类型

下一篇:spring5 源码深度解析----- 事务的回滚和提交(100%理解事务)