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spring boot 源码解析11-ConfigurationClassPostProcessor类加载解析

前言

ConfigurationClassPostProcessor实现了BeanDefinitionRegistryPostProcessor接口,该类会在AbstractApplicationContext#refresh 中的第5步时进行调用.由于其postProcessBeanDefinitionRegistry 实现过程非常复杂,因此单拿一篇进行分析

解析

ConfigurationClassPostProcessor#postProcessBeanDefinitionRegistry 代码如下:

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);
    }

2件事

根据BeanDefinitionRegistry,生成registryId 加入到registriesPostProcessed中.registriesPostProcessed是为了做去重的判断,当重复对一个BeanDefinitionRegistry进行处理时,则会抛出IllegalStateException.

调用processConfigBeanDefinitions 进行类的加载.代码如下:

public void processConfigBeanDefinitions(BeanDefinitionRegistry registry) {
    List<BeanDefinitionHolder> configCandidates = new ArrayList<BeanDefinitionHolder>();
    // 1. 获取已经注册的bean名称
    String[] candidateNames = registry.getBeanDefinitionNames();

    for (String beanName : candidateNames) {
        BeanDefinition beanDef = registry.getBeanDefinition(beanName);
        if (ConfigurationClassUtils.isFullConfigurationClass(beanDef) ||
                ConfigurationClassUtils.isLiteConfigurationClass(beanDef)) {
            // 1.1. 如果BeanDefinition 中的configurationClass 属性为full 或者lite ,则意味着已经处理过了,直接跳过
            if (logger.isDebugEnabled()) {
                logger.debug("Bean definition has already been processed as a configuration class: " + beanDef);
            }
        }
        // 1.2. 判断对应bean是否为配置类,如果是,则加入到configCandidates
        else if (ConfigurationClassUtils.checkConfigurationClassCandidate(beanDef, this.metadataReaderFactory)) {
            configCandidates.add(new BeanDefinitionHolder(beanDef, beanName));
        }
    }

    // Return immediately if no @Configuration classes were found
    // 1.3 如果不存在配置类,则直接return
    if (configCandidates.isEmpty()) {
        return;
    }

    // Sort by previously determined @Order value, if applicable
    // 2. 对configCandidates 进行 排序,按照@Order 配置的值进行排序
    Collections.sort(configCandidates, new Comparator<BeanDefinitionHolder>() {
        @Override
        public int compare(BeanDefinitionHolder bd1, BeanDefinitionHolder bd2) {
            int i1 = ConfigurationClassUtils.getOrder(bd1.getBeanDefinition());
            int i2 = ConfigurationClassUtils.getOrder(bd2.getBeanDefinition());
            return (i1 < i2) ? -1 : (i1 > i2) ? 1 : 0;
        }
    });

    // Detect any custom bean name generation strategy supplied through the enclosing application context
    // 3. 如果BeanDefinitionRegistry 是SingletonBeanRegistry 子类的话,由于我们当前传入的是DefaultListableBeanFactory,是
    // SingletonBeanRegistry 的子类。因此会将registry强转为SingletonBeanRegistry
    SingletonBeanRegistry sbr = null;
    if (registry instanceof SingletonBeanRegistry) {
        sbr = (SingletonBeanRegistry) registry;
        if (!this.localBeanNameGeneratorSet && sbr.containsSingleton(CONFIGURATION_BEAN_NAME_GENERATOR)) {
            // 如果localBeanNameGeneratorSet 等于false 并且SingletonBeanRegistry 中有 id 为 org.springframework.context.annotation.internalConfigurationBeanNameGenerator
            // 的bean .则将componentScanBeanNameGenerator,importBeanNameGenerator 赋值为 该bean.
            BeanNameGenerator generator = (BeanNameGenerator) sbr.getSingleton(CONFIGURATION_BEAN_NAME_GENERATOR);
            this.componentScanBeanNameGenerator = generator;
            this.importBeanNameGenerator = generator;
        }
    }

    // Parse each @Configuration class
    // 4. 实例化ConfigurationClassParser 为了解析 各个配置类
    ConfigurationClassParser parser = new ConfigurationClassParser(
            this.metadataReaderFactory, this.problemReporter, this.environment,
            this.resourceLoader, this.componentScanBeanNameGenerator, registry);

    // 实例化2个set,candidates 用于将之前加入的configCandidates 进行去重
    // alreadyParsed 用于判断是否处理过
    Set<BeanDefinitionHolder> candidates = new LinkedHashSet<BeanDefinitionHolder>(configCandidates);
    Set<ConfigurationClass> alreadyParsed = new HashSet<ConfigurationClass>(configCandidates.size());
    // 5. 进行解析
    do {
        parser.parse(candidates);
        parser.validate();

        Set<ConfigurationClass> configClasses = new LinkedHashSet<ConfigurationClass>(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());
        }
        this.reader.loadBeanDefinitions(configClasses);
        alreadyParsed.addAll(configClasses);

        candidates.clear();
        if (registry.getBeanDefinitionCount() > candidateNames.length) {
            String[] newCandidateNames = registry.getBeanDefinitionNames();
            Set<String> oldCandidateNames = new HashSet<String>(Arrays.asList(candidateNames));
            Set<String> alreadyParsedClasses = new HashSet<String>();
            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
    // 6. 
    if (sbr != null) {
        if (!sbr.containsSingleton(IMPORT_REGISTRY_BEAN_NAME)) {
            // 如果SingletonBeanRegistry 不包含org.springframework.context.annotation.ConfigurationClassPostProcessor.importRegistry
            // 则注册一个,bean 为 ImportRegistry. 一般都会进行注册的
            sbr.registerSingleton(IMPORT_REGISTRY_BEAN_NAME, parser.getImportRegistry());
        }
    }

    // 7. 清除缓存
    if (this.metadataReaderFactory instanceof CachingMetadataReaderFactory) {
        ((CachingMetadataReaderFactory) this.metadataReaderFactory).clearCache();
    }
}

7件事:

获取已经注册的bean名称,进行遍历
1. 如果BeanDefinition 中的configurationClass 属性为full 或者lite ,则意味着已经处理过了,直接跳过
2. 判断对应bean是否为配置类,如果是,则加入到configCandidates.
3. 如果不存在配置类,则直接return
对configCandidates 进行排序,按照@Order 配置的值进行排序
如果BeanDefinitionRegistry 是SingletonBeanRegistry 子类的话,由于我们当前传入的是DefaultListableBeanFactory,是 SingletonBeanRegistry 的子类。因此会将registry强转为SingletonBeanRegistry.
- 如果localBeanNameGeneratorSet 等于false 并且SingletonBeanRegistry 中有 id 为 org.springframework.context.annotation.internalConfigurationBeanNameGenerator的bean .则将componentScanBeanNameGenerator,importBeanNameGenerator 赋值为该bean.
实例化ConfigurationClassParser 为了解析各个配置类.实例化2个set,candidates 用于将之前加入的configCandidates 进行去重,alreadyParsed 用于判断是否处理过
进行解析
1. 调用ConfigurationClassParser#parse进行解析
2. 将解析过的配置类加入到configClasses,并将configClasses去重已经处理过的,以防止重复加载
3. 如果reader为null,则实例化ConfigurationClassBeanDefinitionReader
4. 调用ConfigurationClassBeanDefinitionReader#loadBeanDefinitions 进行加载,并加入到alreadyParsed中,用于去重
5. 将candidates进行清空,如果registry中注册的bean的数量大于之前获得的数量,则意味着在解析过程中又新加入了很多,那么就需要对其进行解析
如果SingletonBeanRegistry 不包含org.springframework.context.annotation.ConfigurationClassPostProcessor.importRegistry,则注册一个,bean 为 ImportRegistry. 一般都会进行注册的
清除缓存

1.2 判断对应bean是否为配置类调用的是ConfigurationClassUtils#checkConfigurationClassCandidate.代码如下:

public static boolean checkConfigurationClassCandidate(BeanDefinition beanDef, MetadataReaderFactory metadataReaderFactory) {
    // 1. 获取类名,如果类名不存在则返回false
    String className = beanDef.getBeanClassName();
    if (className == null) {
        return false;
    }

    // 2. 获得AnnotationMetadata
    AnnotationMetadata metadata;
    if (beanDef instanceof AnnotatedBeanDefinition &&
            className.equals(((AnnotatedBeanDefinition) beanDef).getMetadata().getClassName())) {
        // Can reuse the pre-parsed metadata from the given BeanDefinition...
        // 2.1 如果BeanDefinition 是 AnnotatedBeanDefinition的实例,并且className 和 BeanDefinition中 的元数据 的类名相同
        // 则直接从BeanDefinition 获得Metadata
        metadata = ((AnnotatedBeanDefinition) beanDef).getMetadata();
    }
    else if (beanDef instanceof AbstractBeanDefinition && ((AbstractBeanDefinition) beanDef).hasBeanClass()) {
        // Check already loaded Class if present...
        // since we possibly can't even load the class file for this Class.
        // 2.2 如果BeanDefinition 是 AnnotatedBeanDefinition的实例,并且beanDef 有 beanClass 属性存在
        // 则实例化StandardAnnotationMetadata
        Class<?> beanClass = ((AbstractBeanDefinition) beanDef).getBeanClass();
        metadata = new StandardAnnotationMetadata(beanClass, true);
    }
    else {
        try {
            // 2.3 否则 通过MetadataReaderFactory 中的MetadataReader 进行读取
            MetadataReader metadataReader = metadataReaderFactory.getMetadataReader(className);
            metadata = metadataReader.getAnnotationMetadata();
        }
        catch (IOException ex) {
            if (logger.isDebugEnabled()) {
                logger.debug("Could not find class file for introspecting configuration annotations: " + className, ex);
            }
            return false;
        }
    }

    // 3. 
    if (isFullConfigurationCandidate(metadata)) {
        // 3.1 如果存在Configuration 注解,则为BeanDefinition 设置configurationClass属性为full
        beanDef.setAttribute(CONFIGURATION_CLASS_ATTRIBUTE, CONFIGURATION_CLASS_FULL);
    }
    else if (isLiteConfigurationCandidate(metadata)) {
        // 3.2 如果AnnotationMetadata 中有Component,ComponentScan,Import,ImportResource 注解中的任意一个,或者存在 被@bean 注解的方法,则返回true.
        // 则设置configurationClass属性为lite
        beanDef.setAttribute(CONFIGURATION_CLASS_ATTRIBUTE, CONFIGURATION_CLASS_LITE);
    }
    else {
        // 3.3 返回false
        return false;
    }

    // It's a full or lite configuration candidate... Let's determine the order value, if any.
    // 4. 如果该类被@Order所注解,则设置order属性为@Order的值
    Map<String, Object> orderAttributes = metadata.getAnnotationAttributes(Order.class.getName());
    if (orderAttributes != null) {
        beanDef.setAttribute(ORDER_ATTRIBUTE, orderAttributes.get(AnnotationUtils.VALUE));
    }

    return true;
}

5件事:

获取类名,如果类名不存在则返回false
获得AnnotationMetadata
1. 如果BeanDefinition 是 AnnotatedBeanDefinition的实例,并且className 和 BeanDefinition中的元数据的类名相同,则直接从BeanDefinition 获得Metadata
2. 如果BeanDefinition 是 AnnotatedBeanDefinition的实例,并且beanDef 有 beanClass属性存在,则实例化StandardAnnotationMetadata
3. 否则通过MetadataReaderFactory 中的MetadataReader 进行读取
进行判断
1. 如果存在Configuration 注解,则为BeanDefinition 设置configurationClass属性为full.
2. 如果AnnotationMetadata 中有Component,ComponentScan,Import,ImportResource 注解中的任意一个,或者存在被@bean 注解的方法,则返回true.
3. 否则,返回false
如果该类被@Order所注解,则设置order属性为@Order的值
返回true.

5.1 调用的是ConfigurationClassParser#parse,代码如下:

public void parse(Set<BeanDefinitionHolder> configCandidates) {
    this.deferredImportSelectors = new LinkedList<DeferredImportSelectorHolder>();

            for (BeanDefinitionHolder holder : configCandidates) {
        BeanDefinition bd = holder.getBeanDefinition();
        try {
            if (bd instanceof AnnotatedBeanDefinition) {

                parse(((AnnotatedBeanDefinition) bd).getMetadata(), holder.getBeanName());
            }
            else if (bd instanceof AbstractBeanDefinition && ((AbstractBeanDefinition) bd).hasBeanClass()) {
                parse(((AbstractBeanDefinition) bd).getBeanClass(), holder.getBeanName());
            }
            else {
                parse(bd.getBeanClassName(), holder.getBeanName());
            }
        }
        catch (BeanDefinitionStoreException ex) {
            throw ex;
        }
        catch (Throwable ex) {
            throw new BeanDefinitionStoreException(
                    "Failed to parse configuration class [" + bd.getBeanClassName() + "]", ex);
        }
    }

            processDeferredImportSelectors();
}

3件事

实例化deferredImportSelectors
遍历configCandidates ,进行处理.根据BeanDefinition 的类型做不同的处理,一般都会调用ConfigurationClassParser#parse 进行解析
处理ImportSelect

其中第2步执行的代码如下:

    protected final void parse(AnnotationMetadata metadata, String beanName) throws IOException {
    processConfigurationClass(new ConfigurationClass(metadata, beanName));
}1
2
3

最终调用

protected void processConfigurationClass(ConfigurationClass configClass) throws IOException {
    // 1. 判断是否应该被跳过
    if (this.conditionEvaluator.shouldSkip(configClass.getMetadata(), ConfigurationPhase.PARSE_CONFIGURATION)) {
        return;
    }

    // 2. 处理Imported 的情况
    ConfigurationClass existingClass = this.configurationClasses.get(configClass);
    if (existingClass != null) {
        if (configClass.isImported()) {
            if (existingClass.isImported()) {
                existingClass.mergeImportedBy(configClass);
            }
            // Otherwise ignore new imported config class; existing non-imported class overrides it.
            return;
        }
        else {
            // Explicit bean definition found, probably replacing an import.
            // Let's remove the old one and go with the new one.
            this.configurationClasses.remove(configClass);
            for (Iterator<ConfigurationClass> it = this.knownSuperclasses.values().iterator(); it.hasNext();) {
                if (configClass.equals(it.next())) {
                    it.remove();
                }
            }
        }
    }

    // Recursively process the configuration class and its superclass hierarchy.
    SourceClass sourceClass = asSourceClass(configClass);
    do {
        // 3. 递归调用进行解析
        sourceClass = doProcessConfigurationClass(configClass, sourceClass);
    }
    while (sourceClass != null);

    // 4. 添加到configurationClasses中
    this.configurationClasses.put(configClass, configClass);
}

4件事:

判断是否应该被跳过.通过调用ConditionEvaluator#shouldSkip实现的,代码如下:

public boolean shouldSkip(AnnotatedTypeMetadata metadata, ConfigurationPhase phase) {
// 1. 如果这个类没有被@Conditional注解所修饰，不会skip
if (metadata == null || !metadata.isAnnotated(Conditional.class.getName())) {
    return false;
}

// 2. 如果参数中沒有设置条件注解的生效阶段
if (phase == null) {
    // 是配置类的话直接使用PARSE_CONFIGURATION阶段
    if (metadata instanceof AnnotationMetadata &&
            ConfigurationClassUtils.isConfigurationCandidate((AnnotationMetadata) metadata)) {
        return shouldSkip(metadata, ConfigurationPhase.PARSE_CONFIGURATION);
    }
    // 否则使用REGISTER_BEAN阶段
    return shouldSkip(metadata, ConfigurationPhase.REGISTER_BEAN);
}

List<Condition> conditions = new ArrayList<Condition>(); // 要解析的配置类的条件集合
// 3. 获取配置类的条件注解得到条件数据，并添加到集合中
for (String[] conditionClasses : getConditionClasses(metadata)) {
    for (String conditionClass : conditionClasses) {
        Condition condition = getCondition(conditionClass, this.context.getClassLoader());
        conditions.add(condition);
    }
}

AnnotationAwareOrderComparator.sort(conditions);

// 4. 遍历conditions,进行判断
for (Condition condition : conditions) {
    ConfigurationPhase requiredPhase = null;
    if (condition instanceof ConfigurationCondition) {
        requiredPhase = ((ConfigurationCondition) condition).getConfigurationPhase();
    }
    if (requiredPhase == null || requiredPhase == phase) {
        // 阶段不满足条件的话，返回true并跳过这个bean的解析
        if (!condition.matches(this.context, metadata)) {
            return true;
        }
    }
}

return false;
}

4件事

如果这个类没有被@Conditional注解所修饰，不会skip,返回false
如果参数中沒有设置条件注解的生效阶段
1. 是配置类的话直接使用PARSE_CONFIGURATION阶段,递归调用shouldSkip 进行判断
2. 否则使用REGISTER_BEAN阶段,递归调用shouldSkip 进行判断
获取配置类的条件注解得到条件数据，并添加到集合中
遍历conditions,进行判断,如果阶段不满足条件的话，返回true并跳过这个bean的解析

处理Imported 的情况
递归调用进行解析
添加到configurationClasses中

其中第三步,代码如下:

protected final SourceClass doProcessConfigurationClass(ConfigurationClass configClass, SourceClass sourceClass)
        throws IOException {

    // 1. Recursively process any member (nested) classes first 处理内部类
    processMemberClasses(configClass, sourceClass);

    // 2. Process any @PropertySource annotations  处理@PropertySource
    for (AnnotationAttributes propertySource : AnnotationConfigUtils.attributesForRepeatable(
            sourceClass.getMetadata(), PropertySources.class,
            org.springframework.context.annotation.PropertySource.class)) {
        if (this.environment instanceof ConfigurableEnvironment) {
            processPropertySource(propertySource);
        }
        else {
            logger.warn("Ignoring @PropertySource annotation on [" + sourceClass.getMetadata().getClassName() +
                    "]. Reason: Environment must implement ConfigurableEnvironment");
        }
    }

    // 3. Process any @ComponentScan annotations 处理@ComponentScan
    Set<AnnotationAttributes> componentScans = AnnotationConfigUtils.attributesForRepeatable(
            sourceClass.getMetadata(), ComponentScans.class, ComponentScan.class);
    if (!componentScans.isEmpty() &&
            !this.conditionEvaluator.shouldSkip(sourceClass.getMetadata(), ConfigurationPhase.REGISTER_BEAN)) {
        for (AnnotationAttributes componentScan : componentScans) {
            // The config class is annotated with @ComponentScan -> perform the scan immediately
            // 3.1 进行扫描
            Set<BeanDefinitionHolder> scannedBeanDefinitions =
                    this.componentScanParser.parse(componentScan, sourceClass.getMetadata().getClassName());
            // Check the set of scanned definitions for any further config classes and parse recursively if needed
            // 3.2 依次遍历扫描的配置类进行解析
            for (BeanDefinitionHolder holder : scannedBeanDefinitions) {
                if (ConfigurationClassUtils.checkConfigurationClassCandidate(
                        holder.getBeanDefinition(), this.metadataReaderFactory)) {
                    parse(holder.getBeanDefinition().getBeanClassName(), holder.getBeanName());
                }
            }
        }
    }

    // 4. Process any @Import annotations 处理@Import
    processImports(configClass, sourceClass, getImports(sourceClass), true);

    // 5. Process any @ImportResource annotations
    if (sourceClass.getMetadata().isAnnotated(ImportResource.class.getName())) {
        AnnotationAttributes importResource =
                AnnotationConfigUtils.attributesFor(sourceClass.getMetadata(), ImportResource.class);
        String[] resources = importResource.getStringArray("locations");
        // 遍历配置的locations,加入到configClass 中的ImportedResource
        Class<? extends BeanDefinitionReader> readerClass = importResource.getClass("reader");
        for (String resource : resources) {
            String resolvedResource = this.environment.resolveRequiredPlaceholders(resource);
            configClass.addImportedResource(resolvedResource, readerClass);
        }
    }

    // 6. Process individual @Bean methods
    Set<MethodMetadata> beanMethods = retrieveBeanMethodMetadata(sourceClass);
    // 遍历@Bean注释的方法,添加到configClass
    for (MethodMetadata methodMetadata : beanMethods) {
        configClass.addBeanMethod(new BeanMethod(methodMetadata, configClass));
    }

    // 7. Process default methods on interfaces
    processInterfaces(configClass, sourceClass);

    // 8. Process superclass, if any 如果有父类的话,则返回父类进行进一步的解析
    if (sourceClass.getMetadata().hasSuperClass()) {
        String superclass = sourceClass.getMetadata().getSuperClassName();
        if (!superclass.startsWith("java") && !this.knownSuperclasses.containsKey(superclass)) {
            this.knownSuperclasses.put(superclass, configClass);
            // Superclass found, return its annotation metadata and recurse
            return sourceClass.getSuperClass();
        }
    }

    // No superclass -> processing is complete
    return null;
}

8件事

处理内部类.代码如下:

private void processMemberClasses(ConfigurationClass configClass, SourceClass sourceClass) throws IOException {
// 1. 遍历class中的内部类
for (SourceClass memberClass : sourceClass.getMemberClasses()) {
    if (ConfigurationClassUtils.isConfigurationCandidate(memberClass.getMetadata()) &&
            !memberClass.getMetadata().getClassName().equals(configClass.getMetadata().getClassName())) {
        // 2. 如果该内部类是一个配置类,并且该内部类的类名和configClass的类名不相同
        if (this.importStack.contains(configClass)) {
            // 2.1 如果importStack 包含该configClass的化,则意味发生了循环依赖,则会抛出BeanDefinitionParsingException 异常
            this.problemReporter.error(new CircularImportProblem(configClass, this.importStack));
        }
        else {
            // 2.2 否则加入到importStack,调用processConfigurationClass 进行解析
            this.importStack.push(configClass);
            try {
                processConfigurationClass(memberClass.asConfigClass(configClass));
            }
            finally {
                this.importStack.pop();
            }
        }
    }
}
}

2件事:

遍历class中的内部类
如果该内部类是一个配置类,并且该内部类的类名和configClass的类名不相同
1. 如果importStack 包含该configClass的化,则意味发生了循环依赖,则会抛出BeanDefinitionParsingException 异常
2. 否则加入到importStack,调用processConfigurationClass 进行解析,最后在弹出该configClass.

处理@PropertySource.通过遍历该类中的@PropertySource的注解,如果该类中的environment是ConfigurableEnvironment 子类的话,则调用processPropertySource进行处理.否则打印警告日志.一般都是ConfigurableEnvironment的子类.代码如下:

private void processPropertySource(AnnotationAttributes propertySource) throws IOException {
// 1. 解析name、encoding值
String name = propertySource.getString("name");
if (!StringUtils.hasLength(name)) {
    name = null;
}
String encoding = propertySource.getString("encoding");
if (!StringUtils.hasLength(encoding)) {
    encoding = null;
}
// 2. 解析value（数组）以及ignoreResourceNotFound值
String[] locations = propertySource.getStringArray("value");
Assert.isTrue(locations.length > 0, "At least one @PropertySource(value) location is required");
boolean ignoreResourceNotFound = propertySource.getBoolean("ignoreResourceNotFound");

// 3. 解析factory，如果该值没有配置，默认为PropertySourceFactory则直接实例化DefaultPropertySourceFactory类，否则开始实例化自定义的类
Class<? extends PropertySourceFactory> factoryClass = propertySource.getClass("factory");
PropertySourceFactory factory = (factoryClass == PropertySourceFactory.class ?
        DEFAULT_PROPERTY_SOURCE_FACTORY : BeanUtils.instantiateClass(factoryClass));

for (String location : locations) {
    try {
        // 4.1 对location进行SPEL表达式的解析。比如当前的配置环境中有一个属性为app=shareniu，我们配置的location为${app}最终值为shareniu。通过这里的处理逻辑可以知道location支持多环境的切换以及表达式的配置
        String resolvedLocation = this.environment.resolveRequiredPlaceholders(location);
        // 4.2 使用资源加载器resourceLoader将resolvedLocation抽象为Resource
        Resource resource = this.resourceLoader.getResource(resolvedLocation);
        // 4.3 调用addPropertySource属性进行处理。将指定的资源处理之后，添加到当前springboot运行的环境中
        addPropertySource(factory.createPropertySource(name, new EncodedResource(resource, encoding)));
    }
    catch (IllegalArgumentException ex) {
        // 5. 如果上述的任意步骤报错，则开始查找ignoreResourceNotFound的值，如果该值为treu，则忽略异常，否则直接报错
        // Placeholders not resolvable
        if (ignoreResourceNotFound) {
            if (logger.isInfoEnabled()) {
                logger.info("Properties location [" + location + "] not resolvable: " + ex.getMessage());
            }
        }
        else {
            throw ex;
        }
    }
    catch (IOException ex) {
        // Resource not found when trying to open it
        if (ignoreResourceNotFound &&
                (ex instanceof FileNotFoundException || ex instanceof UnknownHostException)) {
            if (logger.isInfoEnabled()) {
                logger.info("Properties location [" + location + "] not resolvable: " + ex.getMessage());
            }
        }
        else {
            throw ex;
        }
    }
}
}

5件事:

解析name、encoding值
解析value（数组）以及ignoreResourceNotFound值
解析factory，如果该值没有配置，默认为PropertySourceFactory则直接实例化DefaultPropertySourceFactory类，否则开始实例化自定义的类
遍历配置的locations进行处理
1. 对location进行SPEL表达式的解析。比如当前的配置环境中有一个属性为app=shareniu，我们配置的location为${app}最终值为shareniu。通过这里的处理逻辑可以知道location支持多环境的切换以及表达式的配置
2. 使用资源加载器resourceLoader将resolvedLocation抽象为Resource
3. 调用addPropertySource属性进行处理。将指定的资源处理之后，添加到当前springboot运行的环境中

5.如果上述的任意步骤报错，则开始查找ignoreResourceNotFound的值，如果该值为treu，则忽略异常，否则直接报错

处理@ComponentScan,通过遍历该类上的@ComponentScan 注解,并且通过ConditionEvaluator#shouldSkip判断后

依次通过ComponentScanAnnotationParser#parse进行扫描。最终调用ClassPathBeanDefinitionScanner#doScan.代码如下:

protected Set<BeanDefinitionHolder> doScan(String... basePackages) {
Assert.notEmpty(basePackages, "At least one base package must be specified");
Set<BeanDefinitionHolder> beanDefinitions = new LinkedHashSet<BeanDefinitionHolder>();
for (String basePackage : basePackages) {
// 扫描basePackage路径下的java文件
Set<BeanDefinition> candidates = findCandidateComponents(basePackage);
for (BeanDefinition candidate : candidates) {
    // 解析scope属性
    ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(candidate);
    candidate.setScope(scopeMetadata.getScopeName());
    String beanName = this.beanNameGenerator.generateBeanName(candidate, this.registry);
    if (candidate instanceof AbstractBeanDefinition) {
        postProcessBeanDefinition((AbstractBeanDefinition) candidate, beanName);
    }
    if (candidate instanceof AnnotatedBeanDefinition) {
        // 如果是AnnotatedBeanDefinition类型,则检查常用注解:如lazy等
        AnnotationConfigUtils.processCommonDefinitionAnnotations((AnnotatedBeanDefinition) candidate);
    }
    // 检查当前bean是否已经注册
    if (checkCandidate(beanName, candidate)) {
        BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(candidate, beanName);
        // 如果当前bean是用于生成代理的bean那么需要进一步处理
        definitionHolder =
                AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
        beanDefinitions.add(definitionHolder);
        registerBeanDefinition(definitionHolder, this.registry);
    }
}
}
return beanDefinitions;
}

遍历basePackages,通过findCandidateComponents方法扫描basePackage路径下的java文件

如果扫描到文件的话,则遍历之.

解析scope属性
生成beanName.

如果该 BeanDefinition 是AbstractBeanDefinition 的子类的话,则调用postProcessBeanDefinition为其设置默认值.代码如下:

    protected void postProcessBeanDefinition(AbstractBeanDefinition beanDefinition, String beanName) {
beanDefinition.applyDefaults(this.beanDefinitionDefaults);
if (this.autowireCandidatePatterns != null) {
beanDefinition.setAutowireCandidate(PatternMatchUtils.simpleMatch(this.autowireCandidatePatterns, beanName));
}
}1
2
3
4
5
6

为其设置默认值.

    public void applyDefaults(BeanDefinitionDefaults defaults) {
setLazyInit(defaults.isLazyInit());//false
setAutowireMode(defaults.getAutowireMode());//AUTOWIRE_NO
setDependencyCheck(defaults.getDependencyCheck());//DEPENDENCY_CHECK_NONE
setInitMethodName(defaults.getInitMethodName());// null
setEnforceInitMethod(false);
setDestroyMethodName(defaults.getDestroyMethodName());//null
setEnforceDestroyMethod(false);
}

如果autowireCandidatePatterns 不等于null的话,则设置AutowireCandidate.

如果该BeanDefinition是AnnotatedBeanDefinition的子类,则调用AnnotationConfigUtils#processCommonDefinitionAnnotations,检查常用注解:如lazy等

检查当前bean是否已经注册,如果没有注册的话,则

生成BeanDefinitionHolder

如果当前bean是用于生成代理的bean那么需要进一步处理,代码如下:

    static BeanDefinitionHolder applyScopedProxyMode(
ScopeMetadata metadata, BeanDefinitionHolder definition, BeanDefinitionRegistry registry) {
ScopedProxyMode scopedProxyMode = metadata.getScopedProxyMode();
if (scopedProxyMode.equals(ScopedProxyMode.NO)) {
return definition;
}
boolean proxyTargetClass = scopedProxyMode.equals(ScopedProxyMode.TARGET_CLASS);
return ScopedProxyCreator.createScopedProxy(definition, registry, proxyTargetClass);
}

由于一般ScopedProxyMode都是NO,因此也就不会生成代理

添加到beanDefinitions中
向BeanDefinitionRegistry进行注册

依次遍历扫描的配置类进行递归解析.最终又会调用ConfigurationClassParser#processConfigurationClass

处理@Import.代码如下:

    private void processImports(ConfigurationClass configClass, SourceClass currentSourceClass,
    Collection<SourceClass> importCandidates, boolean checkForCircularImports) throws IOException {

// 1. 如果importCandidates为空,则直接return
if (importCandidates.isEmpty()) {
    return;
}

// 2. 进行循环依赖的检查
if (checkForCircularImports && isChainedImportOnStack(configClass)) {
    this.problemReporter.error(new CircularImportProblem(configClass, this.importStack));
}
else {
    this.importStack.push(configClass);
    try {
        // 3. 如果不存在循环依赖,则依次遍历处理之
        for (SourceClass candidate : importCandidates) {
            if (candidate.isAssignable(ImportSelector.class)) {
                // 3.1 如果是ImportSelector的子类
                // Candidate class is an ImportSelector -> delegate to it to determine imports
                Class<?> candidateClass = candidate.loadClass();
                // 则实例化后,调用ParserStrategyUtils#invokeAwareMethods
                ImportSelector selector = BeanUtils.instantiateClass(candidateClass, ImportSelector.class);
                ParserStrategyUtils.invokeAwareMethods(
                        selector, this.environment, this.resourceLoader, this.registry);
                if (this.deferredImportSelectors != null && selector instanceof DeferredImportSelector) {
                    // 3.2 如果当前类是DeferredImportSelector 的实现,则加入到deferredImportSelectors
                    this.deferredImportSelectors.add(
                            new DeferredImportSelectorHolder(configClass, (DeferredImportSelector) selector));
                }
                else {
                    // 3.3 如果不是,则调用processImports 进行处理.
                    String[] importClassNames = selector.selectImports(currentSourceClass.getMetadata());
                    Collection<SourceClass> importSourceClasses = asSourceClasses(importClassNames);
                    processImports(configClass, currentSourceClass, importSourceClasses, false);
                }
            }
            else if (candidate.isAssignable(ImportBeanDefinitionRegistrar.class)) {
                // Candidate class is an ImportBeanDefinitionRegistrar ->
                // delegate to it to register additional bean definitions
                // 如果是ImportBeanDefinitionRegistrar的子类,则实例化后,调用ParserStrategyUtils#invokeAwareMethods,
                // 添加到configClass中
                Class<?> candidateClass = candidate.loadClass();
                ImportBeanDefinitionRegistrar registrar =
                        BeanUtils.instantiateClass(candidateClass, ImportBeanDefinitionRegistrar.class);
                ParserStrategyUtils.invokeAwareMethods(
                        registrar, this.environment, this.resourceLoader, this.registry);
                configClass.addImportBeanDefinitionRegistrar(registrar, currentSourceClass.getMetadata());
            }
            else {
                // Candidate class not an ImportSelector or ImportBeanDefinitionRegistrar ->
                // process it as an @Configuration class
                // 3. 否则，加入到importStack后调用processConfigurationClass 进行处理.
                this.importStack.registerImport(
                        currentSourceClass.getMetadata(), candidate.getMetadata().getClassName());
                processConfigurationClass(candidate.asConfigClass(configClass));
            }
        }
    }
    catch (BeanDefinitionStoreException ex) {
        throw ex;
    }
    catch (Throwable ex) {
        throw new BeanDefinitionStoreException(
                "Failed to process import candidates for configuration class [" +
                configClass.getMetadata().getClassName() + "]", ex);
    }
    finally {
        this.importStack.pop();
    }
}
}

如果@Import注解不存在的话,则直接return.
进行循环依赖的检查,如果存在循环依赖的话,则直接抛出异常
加入importStack中,用于循环依赖的检查,依次遍历 @Import
1. 如果是ImportSelector的子类,则实例化后,调用ParserStrategyUtils#invokeAwareMethods.
  1. 如果当前类是DeferredImportSelector 的实现,则加入到deferredImportSelectors
  2. 如果不是,则调用processImports 进行处理.
2. 如果是ImportBeanDefinitionRegistrar的子类,则实例化后,调用ParserStrategyUtils#invokeAwareMethods,添加到configClass中
3. 否则，加入到importStack后调用processConfigurationClass 进行处理.
最后,从importStack栈顶元素.

其中ParserStrategyUtils#invokeAwareMethods,代码如下:

    public static void invokeAwareMethods(Object parserStrategyBean, Environment environment,
    ResourceLoader resourceLoader, BeanDefinitionRegistry registry) {

if (parserStrategyBean instanceof Aware) {
    if (parserStrategyBean instanceof BeanClassLoaderAware) {
        ClassLoader classLoader = (registry instanceof ConfigurableBeanFactory ?
                ((ConfigurableBeanFactory) registry).getBeanClassLoader() : resourceLoader.getClassLoader());
        ((BeanClassLoaderAware) parserStrategyBean).setBeanClassLoader(classLoader);
    }
    if (parserStrategyBean instanceof BeanFactoryAware && registry instanceof BeanFactory) {
        ((BeanFactoryAware) parserStrategyBean).setBeanFactory((BeanFactory) registry);
    }
    if (parserStrategyBean instanceof EnvironmentAware) {
        ((EnvironmentAware) parserStrategyBean).setEnvironment(environment);
    }
    if (parserStrategyBean instanceof ResourceLoaderAware) {
        ((ResourceLoaderAware) parserStrategyBean).setResourceLoader(resourceLoader);
    }
}
}

如果parserStrategyBean 是Aware 的子类
1. 如果parserStrategyBean是BeanClassLoaderAware的子类,则为其注入ClassLoader
2. 如果parserStrategyBean是BeanFactoryAware的子类并且registry是BeanFactory的子类,则为其注入BeanFactory
3. 如果parserStrategyBean是EnvironmentAware的子类,则为其注入Environment
4. 如果parserStrategyBean是ResourceLoaderAware的子类,则为其注入ResourceLoader
否则不进行处理.

处理@ImportResource,通过获得其@ImportResource,获得locations值后, 遍历配置的locations,加入到configClass 中的ImportedResource.
处理被@Bean注解的方法,遍历@Bean注释的方法,添加到configClass中的BeanMethod

处理接口中被@Bean注解默认方法,代码如下:

private void processInterfaces(ConfigurationClass configClass, SourceClass sourceClass) throws IOException {
// 1. 遍历sourceClass 的接口
for (SourceClass ifc : sourceClass.getInterfaces()) {
    // 2. 获得被@bean注释的方法
    Set<MethodMetadata> beanMethods = retrieveBeanMethodMetadata(ifc);
    for (MethodMetadata methodMetadata : beanMethods) {
        if (!methodMetadata.isAbstract()) {
            // A default method or other concrete method on a Java 8+ interface...
            // 3. 如果不是抽象方法的话,则加入到configClass的BeanMethod
            configClass.addBeanMethod(new BeanMethod(methodMetadata, configClass));
        }
    }
    // 4. 递归处理
    processInterfaces(configClass, ifc);
}
}

遍历sourceClass 的接口
获得被@bean注释的方法
如果不是抽象方法的话,则加入到configClass的BeanMethod
递归调用processInterfaces,看其父接口中是否存在被@bean注解的方法,直到父接口不存在.

如果有父类的话,则返回父类进行进一步的解析,否则返回null

5.4 调用的是ConfigurationClassBeanDefinitionReader#loadBeanDefinitions,代码如下:

    public void loadBeanDefinitions(Set<ConfigurationClass> configurationModel) {
    // 1. 实例化TrackedConditionEvaluator
    TrackedConditionEvaluator trackedConditionEvaluator = new TrackedConditionEvaluator();
    // 2. 遍历configurationModel,依次调用loadBeanDefinitionsForConfigurationClass
    for (ConfigurationClass configClass : configurationModel) {
        loadBeanDefinitionsForConfigurationClass(configClass, trackedConditionEvaluator);
    }
}

2件事:

实例化TrackedConditionEvaluator

遍历configurationModel,依次调用loadBeanDefinitionsForConfigurationClass进行加载.代码如下:

private void loadBeanDefinitionsForConfigurationClass(ConfigurationClass configClass,
    TrackedConditionEvaluator trackedConditionEvaluator) {

// 1. 使用条件注解判断是否需要跳过这个配置类
if (trackedConditionEvaluator.shouldSkip(configClass)) {
    String beanName = configClass.getBeanName();
    // 1.1 跳过配置类的话在Spring容器中移除bean的注册
    if (StringUtils.hasLength(beanName) && this.registry.containsBeanDefinition(beanName)) {
        this.registry.removeBeanDefinition(beanName);
    }
    // 1.2 从importRegistry 进行删除.
    this.importRegistry.removeImportingClass(configClass.getMetadata().getClassName());
    return;
}

if (configClass.isImported()) {
    // 2. 如果自身是被@Import注释所import的，注册自己
    registerBeanDefinitionForImportedConfigurationClass(configClass);
}
// 3. 遍历BeanMethods,依次对其进行注册.
for (BeanMethod beanMethod : configClass.getBeanMethods()) {
    loadBeanDefinitionsForBeanMethod(beanMethod);
}
// 4.注册@ImportResource注解注释的资源文件中的bean
loadBeanDefinitionsFromImportedResources(configClass.getImportedResources());
// 5. 注册@Import注解中的ImportBeanDefinitionRegistrar接口的registerBeanDefinitions
loadBeanDefinitionsFromRegistrars(configClass.getImportBeanDefinitionRegistrars());
}

5件事:

使用条件注解判断是否需要跳过这个配置类,如果需要跳过的话,则Spring容器中移除该bean.并且从importRegistry删除.然后直接return.否则执行第2步.

如果自身是被@Import注解所import的,则调用registerBeanDefinitionForImportedConfigurationClass进行注册.代码如下:

private void registerBeanDefinitionForImportedConfigurationClass(ConfigurationClass configClass) {
// 1. 根据configClass中配置的AnnotationMetadata 实例化AnnotatedGenericBeanDefinition
AnnotationMetadata metadata = configClass.getMetadata();
AnnotatedGenericBeanDefinition configBeanDef = new AnnotatedGenericBeanDefinition(metadata);
// 2 进行属性的设置
// 2.1 解析该configClass的Scope
ScopeMetadata scopeMetadata = scopeMetadataResolver.resolveScopeMetadata(configBeanDef);
configBeanDef.setScope(scopeMetadata.getScopeName());
// 2.2 生成bean的id
String configBeanName = this.importBeanNameGenerator.generateBeanName(configBeanDef, this.registry);
// 2.3 设置bean的一些属性,如LazyInit,Primary等
AnnotationConfigUtils.processCommonDefinitionAnnotations(configBeanDef, metadata);
// 3. 生成BeanDefinitionHolder,并对其尝试进行代理,最后向registry进行注册
BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(configBeanDef, configBeanName);
definitionHolder = AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
this.registry.registerBeanDefinition(definitionHolder.getBeanName(), definitionHolder.getBeanDefinition());
configClass.setBeanName(configBeanName);
if (logger.isDebugEnabled()) {
logger.debug("Registered bean definition for imported class '" + configBeanName + "'");
}
}

3件事

根据configClass中配置的AnnotationMetadata 实例化AnnotatedGenericBeanDefinition
进行属性的设置
1. 解析该configClass的Scope
2. 生成bean的id
3. 设置bean的一些属性,如LazyInit,Primary等
4. 生成BeanDefinitionHolder,并对其尝试进行代理,最后向registry进行注册

遍历BeanMethods,依次对其调用loadBeanDefinitionsForBeanMethod进行注册.代码如下:

private void loadBeanDefinitionsForBeanMethod(BeanMethod beanMethod) {
// 1. 获得声明该BeanMethod的ConfigurationClass
ConfigurationClass configClass = beanMethod.getConfigurationClass();
// 获得BeanMethod的MethodMetadata和methodName
MethodMetadata metadata = beanMethod.getMetadata();
String methodName = metadata.getMethodName();
// Do we need to mark the bean as skipped by its condition?
// 2. 进行判断,是否应该跳过处理
// 2.1 如果ConditionEvaluator#shouldSkip返回true,则添加到configClass的skippedBeanMethods中,return
if (this.conditionEvaluator.shouldSkip(metadata, ConfigurationPhase.REGISTER_BEAN)) {
configClass.skippedBeanMethods.add(methodName);
return;
}
// 2.2 如果configClass的skippedBeanMethods包含该methodName的话,不进行处理,
if (configClass.skippedBeanMethods.contains(methodName)) {
return;
}
// Consider name and any aliases
// 3. 从@Bean 中获得配置的names,如果names不为空的话,则第一个为bean的id,否则该方法名字作为bean的id
AnnotationAttributes bean = AnnotationConfigUtils.attributesFor(metadata, Bean.class);
List<String> names = new ArrayList<String>(Arrays.asList(bean.getStringArray("name")));
String beanName = (!names.isEmpty() ? names.remove(0) : methodName);
// Register aliases even when overridden
// 4. 将names 当做别名进行注册
for (String alias : names) {
this.registry.registerAlias(beanName, alias);
}
// Has this effectively been overridden before (e.g. via XML)?
// 5. 如果存在重复定义的情况,则直接return
if (isOverriddenByExistingDefinition(beanMethod, beanName)) {
return;
}
// 6. 实例化ConfigurationClassBeanDefinition
ConfigurationClassBeanDefinition beanDef = new ConfigurationClassBeanDefinition(configClass, metadata);
beanDef.setResource(configClass.getResource());
beanDef.setSource(this.sourceExtractor.extractSource(metadata, configClass.getResource()));
if (metadata.isStatic()) {
// 6.1  如果该方法是静态的,则将methodName设置为工厂方法
// static @Bean method
beanDef.setBeanClassName(configClass.getMetadata().getClassName());
beanDef.setFactoryMethodName(methodName);
}
else {
// instance @Bean method
// 6.2 如果是实例方法的话,则将configClass的BeanName设置为FactoryBeanName,methodName设置为UniqueFactoryMethodName
beanDef.setFactoryBeanName(configClass.getBeanName());
beanDef.setUniqueFactoryMethodName(methodName);
}
// 6.3 设置AutowireMode 为 构造器注入
beanDef.setAutowireMode(RootBeanDefinition.AUTOWIRE_CONSTRUCTOR);
// 设置skipRequiredCheck属性为true.
beanDef.setAttribute(RequiredAnnotationBeanPostProcessor.SKIP_REQUIRED_CHECK_ATTRIBUTE, Boolean.TRUE);
// 6.4 进行一些常用的属性设置
AnnotationConfigUtils.processCommonDefinitionAnnotations(beanDef, metadata);
Autowire autowire = bean.getEnum("autowire");
if (autowire.isAutowire()) {
beanDef.setAutowireMode(autowire.value());
}
String initMethodName = bean.getString("initMethod");
if (StringUtils.hasText(initMethodName)) {
// 设置 InitMethod
beanDef.setInitMethodName(initMethodName);
}
String destroyMethodName = bean.getString("destroyMethod");
if (destroyMethodName != null) {
// 设置 DestroyMethod
beanDef.setDestroyMethodName(destroyMethodName);
}
// Consider scoping
// 6.5 设置ScopedProxyMode
ScopedProxyMode proxyMode = ScopedProxyMode.NO;
AnnotationAttributes attributes = AnnotationConfigUtils.attributesFor(metadata, Scope.class);
if (attributes != null) {
beanDef.setScope(attributes.getString("value"));
proxyMode = attributes.getEnum("proxyMode");
if (proxyMode == ScopedProxyMode.DEFAULT) {
    proxyMode = ScopedProxyMode.NO;
}
}
// Replace the original bean definition with the target one, if necessary
// 6.6 如果ScopedProxyMode 不等于NO,则生成代理
BeanDefinition beanDefToRegister = beanDef;
if (proxyMode != ScopedProxyMode.NO) {
BeanDefinitionHolder proxyDef = ScopedProxyCreator.createScopedProxy(
        new BeanDefinitionHolder(beanDef, beanName), this.registry,
        proxyMode == ScopedProxyMode.TARGET_CLASS);
beanDefToRegister = new ConfigurationClassBeanDefinition(
        (RootBeanDefinition) proxyDef.getBeanDefinition(), configClass, metadata);
}
if (logger.isDebugEnabled()) {
logger.debug(String.format("Registering bean definition for @Bean method %s.%s()",
        configClass.getMetadata().getClassName(), beanName));
}
// 7. 进行注册
this.registry.registerBeanDefinition(beanName, beanDefToRegister);
}

7件事:

获得声明该BeanMethod的ConfigurationClass,获得BeanMethod的MethodMetadata和methodName
进行判断,是否应该跳过处理
1. 如果ConditionEvaluator#shouldSkip返回true,则添加到configClass的skippedBeanMethods中,return
2. 如果configClass的skippedBeanMethods包含该methodName的话,不进行处理,
从@Bean 中获得配置的names,如果names不为空的话,则第一个为bean的id,否则该方法名字作为bean的id
将names 当做别名进行注册
如果存在重复定义的情况,则直接return
实例化ConfigurationClassBeanDefinition
1. 如果该方法是静态的,则将methodName设置为工厂方法
2. 否则如果是实例方法的话,则将configClass的BeanName设置为FactoryBeanName,methodName设置为UniqueFactoryMethodName
3. 设置AutowireMode 为构造器注入,设置skipRequiredCheck属性为true.
4. 进行一些常用的属性设置
5. 设置 InitMethod
6. 设置 DestroyMethod
7. 设置ScopedProxyMode,如果ScopedProxyMode 不等于NO,则生成代理
进行注册

private void loadBeanDefinitionsFromImportedResources(
Map<String, Class<? extends BeanDefinitionReader>> importedResources) {
Map<Class<?>, BeanDefinitionReader> readerInstanceCache = new HashMap<Class<?>, BeanDefinitionReader>();
// 1. 遍历importedResources
for (Map.Entry<String, Class<? extends BeanDefinitionReader>> entry : importedResources.entrySet()) {
String resource = entry.getKey();
Class<? extends BeanDefinitionReader> readerClass = entry.getValue();

// Default reader selection necessary?
// 2. 选择BeanDefinitionReader
if (BeanDefinitionReader.class == readerClass) {
    if (StringUtils.endsWithIgnoreCase(resource, ".groovy")) {
        // When clearly asking for Groovy, that's what they'll get...
        // 2.1 如果是.groovy,则为GroovyBeanDefinitionReader
        readerClass = GroovyBeanDefinitionReader.class;
    }
    else {
        // Primarily ".xml" files but for any other extension as well
        // 2.2 否则为XmlBeanDefinitionReader,一般都是XmlBeanDefinitionReader
        readerClass = XmlBeanDefinitionReader.class;
    }
}

// 3. 尝试从readerInstanceCache中获取对应的BeanDefinitionReader
BeanDefinitionReader reader = readerInstanceCache.get(readerClass);
if (reader == null) {// 如果不存在,则实例化一个
    try {
        // Instantiate the specified BeanDefinitionReader
        reader = readerClass.getConstructor(BeanDefinitionRegistry.class).newInstance(this.registry);
        // Delegate the current ResourceLoader to it if possible
        if (reader instanceof AbstractBeanDefinitionReader) {
            // 如果reader是AbstractBeanDefinitionReader的子类的话，这个肯定是...
            AbstractBeanDefinitionReader abdr = ((AbstractBeanDefinitionReader) reader);
            abdr.setResourceLoader(this.resourceLoader);
            abdr.setEnvironment(this.environment);
        }
        // 然后放入readerInstanceCache,以防止重复实例化.
        readerInstanceCache.put(readerClass, reader);
    }
    catch (Throwable ex) {
        throw new IllegalStateException(
                "Could not instantiate BeanDefinitionReader class [" + readerClass.getName() + "]");
    }
}
// TODO SPR-6310: qualify relative path locations as done in AbstractContextLoader.modifyLocations
reader.loadBeanDefinitions(resource);}}

3件事:

遍历importedResources
选择BeanDefinitionReader
1. 如果是.groovy结尾的话,则为GroovyBeanDefinitionReader
2. 否则为XmlBeanDefinitionReader,一般都是XmlBeanDefinitionReader
尝试从readerInstanceCache中获取对应的BeanDefinitionReader,如果不存在,则实例化一个,然后放入到readerInstanceCache缓存中
调用BeanDefinitionReader#loadBeanDefinitions进行加载.

由于一般情况下都是XmlBeanDefinitionReader,最终会调用XmlBeanDefinitionReader#loadBeanDefinitions进行加载,这部分属于spring加载xml部分了,碍于篇幅,这里就不在展开了,后续会有文章进行分析的.

private void loadBeanDefinitionsFromRegistrars(Map<ImportBeanDefinitionRegistrar, AnnotationMetadata> registrars) {
for (Map.Entry<ImportBeanDefinitionRegistrar, AnnotationMetadata> entry : registrars.entrySet()) {
entry.getKey().registerBeanDefinitions(entry.getValue(), this.registry);
}
}

只是简单的进行注册.

至此关于bean的加载我们就分析完了.

参考链接

spring boot实战(第十篇)Spring boot Bean加载源码分析

原文地址;https://blog.csdn.net/qq_26000415/article/details/78917682

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原文地址：https://www.cnblogs.com/jpfss/p/11308506.html