SpringBoot 刷新上下文4--处理ComponentScan

SpringBoot刷新上下文一共七篇，基于SpringBoot 2.2.7.RELEASE，Spring 5.2.6.RELEASE
SpringBoot 刷新上下文1–主流程
SpringBoot 刷新上下文2–执行BeanDefinitionRegistryPostProcessor
SpringBoot 刷新上下文3–解析引导类
SpringBoot 刷新上下文4–处理ComponentScan
SpringBoot 刷新上下文5–处理其他注解
SpringBoot 刷新上下文6–加载并注册BeanDefinition
SpringBoot 刷新上下文7–执行BeanFactoryPostProcessor

2.1.3.1.1、处理ComponentScan

2.1.3.1.1.1、扫描获取BeanDefinition

//org.springframework.context.annotation.ComponentScanAnnotationParser#parse
public Set<BeanDefinitionHolder> parse(AnnotationAttributes componentScan, final String declaringClass) {
    //创建扫描器
    ClassPathBeanDefinitionScanner scanner = new ClassPathBeanDefinitionScanner(this.registry,
                                                                                componentScan.getBoolean("useDefaultFilters"), this.environment, this.resourceLoader);

    Class<? extends BeanNameGenerator> generatorClass = componentScan.getClass("nameGenerator");
    boolean useInheritedGenerator = (BeanNameGenerator.class == generatorClass);
    scanner.setBeanNameGenerator(useInheritedGenerator ? this.beanNameGenerator :
                                 BeanUtils.instantiateClass(generatorClass));

    ScopedProxyMode scopedProxyMode = componentScan.getEnum("scopedProxy");
    if (scopedProxyMode != ScopedProxyMode.DEFAULT) {
        scanner.setScopedProxyMode(scopedProxyMode);
    }
    else {
        Class<? extends ScopeMetadataResolver> resolverClass = componentScan.getClass("scopeResolver");
        scanner.setScopeMetadataResolver(BeanUtils.instantiateClass(resolverClass));
    }
	//设置正则 **/*.class
    scanner.setResourcePattern(componentScan.getString("resourcePattern"));
	//设置要包括的类
    for (AnnotationAttributes filter : componentScan.getAnnotationArray("includeFilters")) {
        for (TypeFilter typeFilter : typeFiltersFor(filter)) {
            scanner.addIncludeFilter(typeFilter);
        }
    }
    //要排除的类
    for (AnnotationAttributes filter : componentScan.getAnnotationArray("excludeFilters")) {
        for (TypeFilter typeFilter : typeFiltersFor(filter)) {
            scanner.addExcludeFilter(typeFilter);
        }
    }
	//是否lazy
    boolean lazyInit = componentScan.getBoolean("lazyInit");
    if (lazyInit) {
        scanner.getBeanDefinitionDefaults().setLazyInit(true);
    }
	//扫描包，如果没有单独标注@CompnentScan 并配置扫描包，这里是空
    Set<String> basePackages = new LinkedHashSet<>();
    String[] basePackagesArray = componentScan.getStringArray("basePackages");
    for (String pkg : basePackagesArray) {
        String[] tokenized = StringUtils.tokenizeToStringArray(this.environment.resolvePlaceholders(pkg),
                                                               ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS);
        Collections.addAll(basePackages, tokenized);
    }
    for (Class<?> clazz : componentScan.getClassArray("basePackageClasses")) {
        basePackages.add(ClassUtils.getPackageName(clazz));
    }
    //如果这里扫描包还是空，则将引导类的包名赋值给basePackages，作为默认扫描包
    if (basePackages.isEmpty()) {
        basePackages.add(ClassUtils.getPackageName(declaringClass));
    }

    scanner.addExcludeFilter(new AbstractTypeHierarchyTraversingFilter(false, false) {
        @Override
        protected boolean matchClassName(String className) {
            return declaringClass.equals(className);
        }
    });
    //扫描包并注册 BeanDefinition
    return scanner.doScan(StringUtils.toStringArray(basePackages));
}
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扫描

//org.springframework.context.annotation.ClassPathBeanDefinitionScanner#doScan
protected Set<BeanDefinitionHolder> doScan(String... basePackages) {
    Assert.notEmpty(basePackages, "At least one base package must be specified");
    //保存扫描到的 BeanDefinitionHolder
    Set<BeanDefinitionHolder> beanDefinitions = new LinkedHashSet<>();
    //遍历所有扫描包路径
    for (String basePackage : basePackages) {
        //扫描路径获取候选类
        Set<BeanDefinition> candidates = findCandidateComponents(basePackage);
        for (BeanDefinition candidate : candidates) {
            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);
            }
            //注解标注类
            if (candidate instanceof AnnotatedBeanDefinition) {
                //处理通用注解
                AnnotationConfigUtils.processCommonDefinitionAnnotations((AnnotatedBeanDefinition) candidate);
            }
            //校验
            if (checkCandidate(beanName, candidate)) {
                BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(candidate, beanName);
                definitionHolder =
                    AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
                beanDefinitions.add(definitionHolder);
                //注册
                registerBeanDefinition(definitionHolder, this.registry);
            }
        }
    }
    return beanDefinitions;
}
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//org.springframework.context.annotation.ClassPathScanningCandidateComponentProvider#findCandidateComponents
public Set<BeanDefinition> findCandidateComponents(String basePackage) {
    if (this.componentsIndex != null && indexSupportsIncludeFilters()) {
        return addCandidateComponentsFromIndex(this.componentsIndex, basePackage);
    }
    else {
        return scanCandidateComponents(basePackage);
    }
}
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扫描包，获取BeanDefinition

static final String DEFAULT_RESOURCE_PATTERN = "**/*.class";
private String resourcePattern = DEFAULT_RESOURCE_PATTERN;
//org.springframework.context.annotation.ClassPathScanningCandidateComponentProvider#scanCandidateComponents
private Set<BeanDefinition> scanCandidateComponents(String basePackage) {
    Set<BeanDefinition> candidates = new LinkedHashSet<>();
    try {
        //扫描包下面的所有.class为后缀的资源
        //resolveBasePackage 会将占位符解析，获得真正的路径
        //String CLASSPATH_ALL_URL_PREFIX = "classpath*:";
        String packageSearchPath = ResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX + resolveBasePackage(basePackage) + '/' + this.resourcePattern;
        //获得所有的资源
        Resource[] resources = getResourcePatternResolver().getResources(packageSearchPath);
        boolean traceEnabled = logger.isTraceEnabled();
        boolean debugEnabled = logger.isDebugEnabled();
        //循环所有的资源
        for (Resource resource : resources) {
            if (traceEnabled) {
                logger.trace("Scanning " + resource);
            }
            //可读的
            if (resource.isReadable()) {
                try {
                    //获取注解元数据
                    MetadataReader metadataReader = getMetadataReaderFactory().getMetadataReader(resource);
                    //判断，这里会检查所有的exclude和include 和 condition
                    if (isCandidateComponent(metadataReader)) {
                        //创建BeanDefinition
                        ScannedGenericBeanDefinition sbd = new ScannedGenericBeanDefinition(metadataReader);
                        //将资源添加到BeanDefinition
                        sbd.setSource(resource);
                        //检查
                        if (isCandidateComponent(sbd)) {
                            if (debugEnabled) {
                                logger.debug("Identified candidate component class: " + resource);
                            }
                            //将BeanDefinition添加到集合
                            candidates.add(sbd);
                        }
                        else {
                            if (debugEnabled) {
                                logger.debug("Ignored because not a concrete top-level class: " + resource);
                            }
                        }
                    }
                    else {
                        if (traceEnabled) {
                            logger.trace("Ignored because not matching any filter: " + resource);
                        }
                    }
                }
                catch (Throwable ex) {
                    throw new BeanDefinitionStoreException(
                        "Failed to read candidate component class: " + resource, ex);
                }
            }
            else {
                if (traceEnabled) {
                    logger.trace("Ignored because not readable: " + resource);
                }
            }
        }
    }
    catch (IOException ex) {
        throw new BeanDefinitionStoreException("I/O failure during classpath scanning", ex);
    }
    return candidates;
}
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处理通用注解

//org.springframework.context.annotation.AnnotationConfigUtils#processCommonDefinitionAnnotations(org.springframework.beans.factory.annotation.AnnotatedBeanDefinition, org.springframework.core.type.AnnotatedTypeMetadata)
static void processCommonDefinitionAnnotations(AnnotatedBeanDefinition abd, AnnotatedTypeMetadata metadata) {
    AnnotationAttributes lazy = attributesFor(metadata, Lazy.class);
    if (lazy != null) {
        abd.setLazyInit(lazy.getBoolean("value"));
    }
    else if (abd.getMetadata() != metadata) {
        lazy = attributesFor(abd.getMetadata(), Lazy.class);
        if (lazy != null) {
            abd.setLazyInit(lazy.getBoolean("value"));
        }
    }

    if (metadata.isAnnotated(Primary.class.getName())) {
        abd.setPrimary(true);
    }
    AnnotationAttributes dependsOn = attributesFor(metadata, DependsOn.class);
    if (dependsOn != null) {
        abd.setDependsOn(dependsOn.getStringArray("value"));
    }

    AnnotationAttributes role = attributesFor(metadata, Role.class);
    if (role != null) {
        abd.setRole(role.getNumber("value").intValue());
    }
    AnnotationAttributes description = attributesFor(metadata, Description.class);
    if (description != null) {
        abd.setDescription(description.getString("value"));
    }
}
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是个具体类(不是接口) ，并且 是 实现类或者是包含@Lookup注解的抽象类。

//org.springframework.context.annotation.ClassPathScanningCandidateComponentProvider#isCandidateComponent(org.springframework.beans.factory.annotation.AnnotatedBeanDefinition)
protected boolean isCandidateComponent(AnnotatedBeanDefinition beanDefinition) {
    AnnotationMetadata metadata = beanDefinition.getMetadata();
    return (metadata.isIndependent() && (metadata.isConcrete() || (metadata.isAbstract() && metadata.hasAnnotatedMethods(Lookup.class.getName()))));
}
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2.1.3.1.1.2、解析被扫描包扫描到的配置类

这里解析自己配置的bean

//org.springframework.context.annotation.ConfigurationClassParser#parse(java.lang.String, java.lang.String)
protected final void parse(@Nullable String className, String beanName) throws IOException {
    Assert.notNull(className, "No bean class name for configuration class bean definition");
    //SimpleMetadataReader
    MetadataReader reader = this.metadataReaderFactory.getMetadataReader(className);
    // 同 前面的 processConfigurationClass 实际上造成了一个递归
    processConfigurationClass(new ConfigurationClass(reader, beanName), DEFAULT_EXCLUSION_FILTER);
}
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