SpringBoot配置类解析流程分析

xw大约 5 分钟SpringSpring Boot

SpringBoot配置类解析流程分析

配置类解析类：org.springframework.context.annotation.ConfigurationClassPostProcessor。

查看postProcessBeanDefinitionRegistry方法，对应代码如下：

@Override
	public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) {
        //获取registrryId
		int registryId = System.identityHashCode(registry);
        //如果已经注册或者已经处理，抛异常   
        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);
		}
        //加入集合
		this.registriesPostProcessed.add(registryId);

		processConfigBeanDefinitions(registry);
	}

进入processConfigBeanDefinitions,底层实现核心方法为doProcessConfigurationClass，总共分为8大部分，分别是对内部类、PropertySource注解、ComponentScan注解、@Import注解、@ImportResource注解、@Bean注解及接口默认方法的处理。

protected final SourceClass doProcessConfigurationClass(ConfigurationClass configClass, SourceClass sourceClass)
			throws IOException {
        //是否使用Component注解
		if (configClass.getMetadata().isAnnotated(Component.class.getName())) {
			// 对内部类进行处理，
			processMemberClasses(configClass, sourceClass);
		}

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

		// 处理@ComponentScan注解
		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
				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
				for (BeanDefinitionHolder holder : scannedBeanDefinitions) {
					BeanDefinition bdCand = holder.getBeanDefinition().getOriginatingBeanDefinition();
					if (bdCand == null) {
						bdCand = holder.getBeanDefinition();
					}
					if (ConfigurationClassUtils.checkConfigurationClassCandidate(bdCand, this.metadataReaderFactory)) {
						parse(bdCand.getBeanClassName(), holder.getBeanName());
					}
				}
			}
		}

		// 处理@Import注解
		processImports(configClass, sourceClass, getImports(sourceClass), true);

		// 处理@ImportResource注解
		AnnotationAttributes importResource =
				AnnotationConfigUtils.attributesFor(sourceClass.getMetadata(), ImportResource.class);
		if (importResource != null) {
			String[] resources = importResource.getStringArray("locations");
			Class<? extends BeanDefinitionReader> readerClass = importResource.getClass("reader");
			for (String resource : resources) {
				String resolvedResource = this.environment.resolveRequiredPlaceholders(resource);
				configClass.addImportedResource(resolvedResource, readerClass);
			}
		}

		// 处理@Bean方法
		Set<MethodMetadata> beanMethods = retrieveBeanMethodMetadata(sourceClass);
		for (MethodMetadata methodMetadata : beanMethods) {
			configClass.addBeanMethod(new BeanMethod(methodMetadata, configClass));
		}

		// 处理接口默认方法
		processInterfaces(configClass, sourceClass);

		// 对父类进行处理
		if (sourceClass.getMetadata().hasSuperClass()) {
			String superclass = sourceClass.getMetadata().getSuperClassName();
			if (superclass != null && !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;
	}

0x1 内部类处理关键方法

private void processMemberClasses(ConfigurationClass configClass, SourceClass sourceClass,
			Predicate<String> filter) throws IOException {
        // 获取内部类
		Collection<SourceClass> memberClasses = sourceClass.getMemberClasses();
		if (!memberClasses.isEmpty()) {
			List<SourceClass> candidates = new ArrayList<>(memberClasses.size());
			for (SourceClass memberClass : memberClasses) {
                // 判断该内部类是否使用了@Component,@ComponentScan,@Import,@ImportResource
                // @Bean注解,并且类名不能与configClass一致
				if (ConfigurationClassUtils.isConfigurationCandidate(memberClass.getMetadata()) &&
						!memberClass.getMetadata().getClassName().equals(configClass.getMetadata().getClassName())) {
					candidates.add(memberClass);
				}
			}
            // 排序
			OrderComparator.sort(candidates);
			for (SourceClass candidate : candidates) {
                // 这里的importstack实际上是一个ArrayDeque,可以当做栈使用，主要是判断有没有循环引用                 //    依赖
				if (this.importStack.contains(configClass)) {
					this.problemReporter.error(new CircularImportProblem(configClass, this.importStack));
				}
				else {
					this.importStack.push(configClass);
					try {
                        // 处理配置类
						processConfigurationClass(candidate.asConfigClass(configClass), filter);
					}
					finally {
						this.importStack.pop();
					}
				}
			}
		}
	}

0x2 @PropertySource注解处理关键方法

类地址：org.springframework.context.annotation.ConfigurationClassParser#processPropertySource

private void processPropertySource(AnnotationAttributes propertySource) throws IOException {
		String name = propertySource.getString("name");
		if (!StringUtils.hasLength(name)) {
			name = null;
		}
		String encoding = propertySource.getString("encoding");
		if (!StringUtils.hasLength(encoding)) {
			encoding = null;
		}
        // 获取配置文件，如classpath:a.properties
		String[] locations = propertySource.getStringArray("value");
		Assert.isTrue(locations.length > 0, "At least one @PropertySource(value) location is required");
		boolean ignoreResourceNotFound = propertySource.getBoolean("ignoreResourceNotFound");

		Class<? extends PropertySourceFactory> factoryClass = propertySource.getClass("factory");
		PropertySourceFactory factory = (factoryClass == PropertySourceFactory.class ?
				DEFAULT_PROPERTY_SOURCE_FACTORY : BeanUtils.instantiateClass(factoryClass));

		for (String location : locations) {
			try {
                // 处理${}占位符
				String resolvedLocation = this.environment.resolveRequiredPlaceholders(location);
				Resource resource = this.resourceLoader.getResource(resolvedLocation);
				// 将 
                addPropertySource(factory.createPropertySource(name, new EncodedResource(resource, encoding)));
			}
			catch (IllegalArgumentException | FileNotFoundException | UnknownHostException | SocketException ex) {
				// Placeholders not resolvable or resource not found when trying to open it
				if (ignoreResourceNotFound) {
					if (logger.isInfoEnabled()) {
						logger.info("Properties location [" + location + "] not resolvable: " + ex.getMessage());
					}
				}
				else {
					throw ex;
				}
			}
		}
	}

0x3 @ComponentScan处理方法

public Set<BeanDefinitionHolder> parse(AnnotationAttributes componentScan, final String declaringClass) {
		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));
		}

		scanner.setResourcePattern(componentScan.getString("resourcePattern"));

		for (AnnotationAttributes filter : componentScan.getAnnotationArray("includeFilters")) {
			for (TypeFilter typeFilter : typeFiltersFor(filter)) {
				scanner.addIncludeFilter(typeFilter);
			}
		}
		for (AnnotationAttributes filter : componentScan.getAnnotationArray("excludeFilters")) {
			for (TypeFilter typeFilter : typeFiltersFor(filter)) {
				scanner.addExcludeFilter(typeFilter);
			}
		}

		boolean lazyInit = componentScan.getBoolean("lazyInit");
		if (lazyInit) {
			scanner.getBeanDefinitionDefaults().setLazyInit(true);
		}

		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));
		}
        //如果没有指定包名，则默认为当前类所在包，并且加入默认过滤,只有注解类会被扫描
		if (basePackages.isEmpty()) {
			basePackages.add(ClassUtils.getPackageName(declaringClass));
		}

		scanner.addExcludeFilter(new AbstractTypeHierarchyTraversingFilter(false, false) {
			@Override
			protected boolean matchClassName(String className) {
				return declaringClass.equals(className);
			}
		});
		return scanner.doScan(StringUtils.toStringArray(basePackages));
	}

0x4 @Import处理方法

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

		if (importCandidates.isEmpty()) {
			return;
		}
         // 判断是不是循环依赖
		if (checkForCircularImports && isChainedImportOnStack(configClass)) {
			this.problemReporter.error(new CircularImportProblem(configClass, this.importStack));
		}
		else {
			this.importStack.push(configClass);
			try {
				for (SourceClass candidate : importCandidates) {
			        //判断是不是ImportSelector的子类
					if (candidate.isAssignable(ImportSelector.class)) {
						// Candidate class is an ImportSelector -> delegate to it to determine imports
						Class<?> candidateClass = candidate.loadClass();
						ImportSelector selector = BeanUtils.instantiateClass(candidateClass, ImportSelector.class);
						ParserStrategyUtils.invokeAwareMethods(
								selector, this.environment, this.resourceLoader, this.registry);         
						//判断是不是DeferredImportSelector子类
						if (selector instanceof DeferredImportSelector) {
							this.deferredImportSelectorHandler.handle(configClass, (DeferredImportSelector) selector);
						}
						else {
							String[] importClassNames = selector.selectImports(currentSourceClass.getMetadata());
							Collection<SourceClass> importSourceClasses = asSourceClasses(importClassNames);
							processImports(configClass, currentSourceClass, importSourceClasses, false);
						}
					}
					// 继承ImportBeanDefinitionRegistrar类的处理逻辑
					else if (candidate.isAssignable(ImportBeanDefinitionRegistrar.class)) {
						// Candidate class is an ImportBeanDefinitionRegistrar ->
						// delegate to it to register additional bean definitions
						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());
					}
					// 默认处理逻辑
					else {
						// Candidate class not an ImportSelector or ImportBeanDefinitionRegistrar ->
						// process it as an @Configuration class
						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();
			}
		}
	}

该方法对几种类进行了处理，分别是

实现ImportSelector类

public class MyImportSelector implements ImportSelector {
    @Override
    public String[] selectImports(AnnotationMetadata importingClassMetadata) {
        System.out.println("MyImportSelector");
        return new String[]{"com.sb2.ioc.xml.Cat", "com.sb2.ioc.xml.Dog"};
    }
}

实现DeferredImportSelector类

public class MyDeferredImportSelector implements DeferredImportSelector {
    @Override
    public String[] selectImports(AnnotationMetadata importingClassMetadata) {
        System.out.println("MyDeferredImportSelector");
        return new String[]{"com.sb2.ioc.xml.Bird", "com.sb2.ioc.xml.Monkey"};
    }
}

实现ImportBeanDefinitionRegistrar类


public class MyBeanImport implements ImportBeanDefinitionRegistrar {

    @Override
    public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
        RootBeanDefinition rootBeanDefinition = new RootBeanDefinition();
        rootBeanDefinition.setBeanClass(Bird.class);
        registry.registerBeanDefinition("bird", rootBeanDefinition);
       
    }
}

0x5 @ImportResource处理方法

AnnotationAttributes importResource =
				AnnotationConfigUtils.attributesFor(sourceClass.getMetadata(), ImportResource.class);
		if (importResource != null) {
		    // 获取路径
			String[] resources = importResource.getStringArray("locations");
			Class<? extends BeanDefinitionReader> readerClass = importResource.getClass("reader");
			for (String resource : resources) {
			    // 占位符代替
				String resolvedResource = this.environment.resolveRequiredPlaceholders(resource);
				configClass.addImportedResource(resolvedResource, readerClass);
			}
		}

总结

各注解处理总结：

@PropertySource : 遍历指定路径，替换占位符，加载资源，将资源添加到environment中，如果资源名相同，做合并处理
@ComponentScan处理：扫描配置类路径，如果没有配置类路径，使用配置类所在路径，过滤顺序excludeFilters->includeFilters->false
@Import处理：如果实现ImportSelector或DeffrredImportSelector,处理实现selectInports返回的类名数组，DeferredImportSelector接口调用优先级低于其他接口。然后判断是否实现ImportBeanDefinitionRegistrar,如果是就处理需要注册的bean，最后处理@Import
@ImportResource处理：将注解属性值放入importedResources中，后续loadBeanDefinitionsForConfigurationClass中加载定义的bean
BeanMethod处理：构造BeanMethod对象放入配置类属性中后续处理。
接口默认方法：与BeanMethod类似。

SpringBoot配置类解析流程分析

# SpringBoot配置类解析流程分析

# 0x1 内部类处理关键方法

# 0x2 @PropertySource注解处理关键方法

# 0x3 @ComponentScan处理方法

# 0x4 @Import处理方法

# 0x5 @ImportResource处理方法

# 总结

SpringBoot配置类解析流程分析

0x1 内部类处理关键方法

0x2 @PropertySource注解处理关键方法

0x3 @ComponentScan处理方法

0x4 @Import处理方法

0x5 @ImportResource处理方法

总结