spring源码解读 -- @Configuration配置类解析流程详解
org.springframework.context.annotation.ConfigurationClassPostProcessor#processConfigBeanDefinitions
本次来探讨下spring是如何解析配置类（即添加了@Configuration的类）
一、环境搭建
POM文件依赖如下：
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0modelVersion>
<groupId>cn.szyrmgroupId>
<artifactId>spring-sourceartifactId>
<version>1.0-SNAPSHOTversion>
<properties>
<maven.compiler.target>1.8maven.compiler.target>
<maven.compiler.source>1.8maven.compiler.source>
<spring-version>5.2.5.RELEASEspring-version>
properties>
<dependencies>
<dependency>
<groupId>org.springframeworkgroupId>
<artifactId>spring-coreartifactId>
<version>${spring-version}version>
dependency>
<dependency>
<groupId>org.springframeworkgroupId>
<artifactId>spring-contextartifactId>
<version>${spring-version}version>
dependency>
<dependency>
<groupId>org.springframeworkgroupId>
<artifactId>spring-beansartifactId>
<version>${spring-version}version>
dependency>
<dependency>
<groupId>org.springframeworkgroupId>
<artifactId>spring-expressionartifactId>
<version>${spring-version}version>
dependency>
dependencies>
project>
二、测试
1、POJO类
package cn.szyrm.spring;
/**
* 这个类在演示中，我们将会通过用配置
* 在标注有@Bean方法进行配置
*/
public class Car {
private String name;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
2、配置类
@Configuration
public class AppConfig {
@Bean
public Car car(){
return new Car();
}
}
3、启动测试类
public class ApplicationTest {
public static void main(String[] args) {
ApplicationContext context = new AnnotationConfigApplicationContext (AppConfig.class);
Car car = context.getBean(Car.class);
Assert.notNull(car,"容器中未查询到对应bean");
}
}
4、运行ApplicationTest 类，发现没有异常。说明已经正确配置
三、源码解读
1、一步一步查找源码入口
这里我们既然是查看怎么解析Configuration配置类
-
1）我们使用全局搜索
Configuration.class发现有如下地方使用：
-
2）、通过上面的搜索，发现是通过
org.springframework.context.annotation.AnnotationConfigUtils#registerAnnotationConfigProcessors(org.springframework.beans.factory.support.BeanDefinitionRegistry,java.lang.Object)注入到spring中的。 -
3）、搜索上面方法的调用位置
-
4）、查看具体调用的位置
- 5）、追溯到最终调用的位置
通过上面的分析，我们发现往spring 容器中注册了ConfigurationClassPostProcessor 这个工厂后置处理器，那么我们可以借助IDEA工具来查找spring 具体是什么时候实例这个对象？以及实例化该对象后所做的事情？
-
6)、在
ConfigurationClassPostProcessor类声明上添加断点 -
7）、以debug模式启动main方法
这里补充一个知识点，从ConfigurationClassPostProcessor定义可以看出其实现了BeanDefinitionRegistryPostProcessor，那么在初始化完成后，就会调用接口中的相应方法进行处理。下面我们来通过源码进行追踪下。
8）、postProcessBeanDefinitionRegistry 方法的调用
由于该后置处理器同时实现了PriorityOrdered接口，所有会被最先调用。
org.springframework.context.support.PostProcessorRegistrationDelegate#invokeBeanDefinitionRegistryPostProcessors 方法就会调用我们要继续调用的方法：org.springframework.context.annotation.ConfigurationClassPostProcessor#postProcessBeanDefinitionRegistry 。
/**
* Derive further bean definitions from the configuration classes in the registry.
*/
@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);
}
9）、postProcessBeanFactory 方法调用
2、核心类方法解析
1)、processConfigBeanDefinitions(registry)方法解读
/**
* Build and validate a configuration model based on the registry of
* {@link Configuration} classes.
*/
public void processConfigBeanDefinitions(BeanDefinitionRegistry registry) {
//1、获取当前beanfactory中的所有的bean的定义信息
List<BeanDefinitionHolder> configCandidates = new ArrayList<>();
String[] candidateNames = registry.getBeanDefinitionNames();
for (String beanName : candidateNames) {
// ...省略部分代码
//2、如果候选的bean是配置类--> 被 @Configuration 注释的类，那么就将其添加到候选的列表
if (ConfigurationClassUtils.checkConfigurationClassCandidate(beanDef, this.metadataReaderFactory)) {
configCandidates.add(new BeanDefinitionHolder(beanDef, beanName));
}
}
//3、新建ConfigurationClassParser,用来解析配置类
// Parse each @Configuration class
ConfigurationClassParser parser = new ConfigurationClassParser(
this.metadataReaderFactory, this.problemReporter, this.environment,
this.resourceLoader, this.componentScanBeanNameGenerator, registry);
Set<BeanDefinitionHolder> candidates = new LinkedHashSet<>(configCandidates);
do {
parser.parse(candidates);
parser.validate();
// ...省略部分代码
//在配置类中配置的bean 注册到容器中
this.reader.loadBeanDefinitions(configClasses);
//...省略部分代码
}
while (!candidates.isEmpty());
// ...省略部分代码
}
processConfigBeanDefinitions(registry)方法主要做了如下事情：
- 1、获取spring 容器有的被@Configuration注释的类
- 2、新建了一个ConfigurationClassParser类
- 3、调用第二步新建的parser类，对候选的配置进行解析操作
- 4、从解析好的配置中读取bean的定义并注册到容器中
2）、解析所有候选的配置类
ConfigurationClassParser#parse(java.util.Set
在这个方法中，我们重点注意关注org.springframework.context.annotation.ConfigurationClassParser#doProcessConfigurationClass ,该方法的源码如下：
@Nullable
protected final SourceClass doProcessConfigurationClass(
ConfigurationClass configClass, SourceClass sourceClass, Predicate<String> filter)
throws IOException {
if (configClass.getMetadata().isAnnotated(Component.class.getName())) {
// 1、首先递归地解析所有的内部类
processMemberClasses(configClass, sourceClass, filter);
}
// 2、处理所有的@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");
}
}
// 3、处理所有的 @ComponentScan annotations
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());
}
}
}
}
// 4、Process any @Import annotations
processImports(configClass, sourceClass, getImports(sourceClass), filter, true);
// 5、Process any @ImportResource annotations
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);
}
}
// 6、Process individual @Bean methods
Set<MethodMetadata> beanMethods = retrieveBeanMethodMetadata(sourceClass);
for (MethodMetadata methodMetadata : beanMethods) {
configClass.addBeanMethod(new BeanMethod(methodMetadata, configClass));
}
//7、 Process default methods on interfaces
processInterfaces(configClass, sourceClass);
// Process superclass, if any
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;
}
可以看出doProcessConfigurationClass 方法是整个解析的核心，主要针对配置类上的各个注解进行了解析
- 1、解析配置类中的每一个内部类
- 2、解析并加载配置类中加载的配置文件
- 3、处理所有的 @ComponentScan、@ComponentScans注解
- 4、处理所有的@Import注解
- 5、处理所有的@ImportResource
- 6、处理所有的添加@Bean的方法
- 7、处理配置类接口中添加@Bean注解的方法
接下来我们将分析里面各个方法的具体实现：
解析配置类中的每一个内部类
/**
* Register member (nested) classes that happen to be configuration classes themselves.
*/
private void processMemberClasses(ConfigurationClass configClass, SourceClass sourceClass,
Predicate<String> filter) throws IOException {
//1、获取所有的内部类
Collection<SourceClass> memberClasses = sourceClass.getMemberClasses();
if (!memberClasses.isEmpty()) {
List<SourceClass> candidates = new ArrayList<>(memberClasses.size());
for (SourceClass memberClass : memberClasses) {
if (ConfigurationClassUtils.isConfigurationCandidate(memberClass.getMetadata()) &&
!memberClass.getMetadata().getClassName().equals(configClass.getMetadata().getClassName())) {
candidates.add(memberClass);
}
}
OrderComparator.sort(candidates);
for (SourceClass candidate : candidates) {
if (this.importStack.contains(configClass)) {
this.problemReporter.error(new CircularImportProblem(configClass, this.importStack));
}
else {
this.importStack.push(configClass);
try {
//2、依次解析每一个配置类
processConfigurationClass(candidate.asConfigClass(configClass), filter);
}
finally {
this.importStack.pop();
}
}
}
}
}
上面的方法是获取到配置类中的所有标记了@Configuration的内部类，然后在对这些候选的配置进行解析操作。
解析并加载配置类中加载的配置文件
/**
* Process the given @PropertySource annotation metadata.
* @param propertySource metadata for the @PropertySource annotation found
* @throws IOException if loading a property source failed
*/
private void processPropertySource(AnnotationAttributes propertySource) throws IOException {
//... 省略部分代码
//1、获取属性文件的位置
String[] locations = propertySource.getStringArray("value");
// ... 省略部分代码
for (String location : locations) {
try {
String resolvedLocation = this.environment.resolveRequiredPlaceholders(location);
//2、根据位置信息来创建资源信息
Resource resource = this.resourceLoader.getResource(resolvedLocation);
//3、将属性文件配置到添加到系统环境中
addPropertySource(factory.createPropertySource(name, new EncodedResource(resource, encoding)));
// ... 省略部分代码
}
}
}
包扫描处理—处理所有的 @ComponentScan、@ComponentScans注解
//1、从元数据中获取到进行包扫描的值
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
// 2、使用componentScanParser进行包扫描
Set<BeanDefinitionHolder> scannedBeanDefinitions =
this.componentScanParser.parse(componentScan, sourceClass.getMetadata().getClassName());
// 3、包扫描到的所有的bean中可能还存在配置类，这时候我们又需要对这些配置类递归地进行解析
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());
}
}
}
}
可以看出该段代码的核心是 使用componentScanParser进行包扫描
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));
}
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));
}
上面就是使用ClassPathBeanDefinitionScanner来进行扫描的。
处理所有的@Import注解
private void processImports(ConfigurationClass configClass, SourceClass currentSourceClass,
Collection<SourceClass> importCandidates, Predicate<String> exclusionFilter,
boolean checkForCircularImports) {
if (importCandidates.isEmpty()) {
return;
}
if (checkForCircularImports && isChainedImportOnStack(configClass)) {
this.problemReporter.error(new CircularImportProblem(configClass, this.importStack));
}
else {
this.importStack.push(configClass);
try {
for (SourceClass candidate : importCandidates) {
if (candidate.isAssignable(ImportSelector.class)) {
// Candidate class is an ImportSelector -> delegate to it to determine imports
Class<?> candidateClass = candidate.loadClass();
ImportSelector selector = ParserStrategyUtils.instantiateClass(candidateClass, ImportSelector.class,
this.environment, this.resourceLoader, this.registry);
Predicate<String> selectorFilter = selector.getExclusionFilter();
if (selectorFilter != null) {
exclusionFilter = exclusionFilter.or(selectorFilter);
}
if (selector instanceof DeferredImportSelector) {
this.deferredImportSelectorHandler.handle(configClass, (DeferredImportSelector) selector);
}
else {
String[] importClassNames = selector.selectImports(currentSourceClass.getMetadata());
Collection<SourceClass> importSourceClasses = asSourceClasses(importClassNames, exclusionFilter);
processImports(configClass, currentSourceClass, importSourceClasses, exclusionFilter, false);
}
}
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 =
ParserStrategyUtils.instantiateClass(candidateClass, ImportBeanDefinitionRegistrar.class,
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
this.importStack.registerImport(
currentSourceClass.getMetadata(), candidate.getMetadata().getClassName());
processConfigurationClass(candidate.asConfigClass(configClass), exclusionFilter);
}
}
}
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();
}
}
}
该方法主要的逻辑是：
-
1、首先处理实现了
ImportSelector接口的类 -
2、处理实现了
ImportBeanDefinitionRegistrar接口的类 -
3、将导入的类作为一个配置类来进行处理
处理所有的@ImportSource
// Process any @ImportResource annotations
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);
}
}
主要逻辑：
- 1、获取配置类上的
ImportResource注解 - 2、获取配置的文件位置信息
- 3、将解析的信息添加到
configClass中
处理所有的@Bean methods
Set<MethodMetadata> beanMethods = retrieveBeanMethodMetadata(sourceClass);
for (MethodMetadata methodMetadata : beanMethods) {
configClass.addBeanMethod(new BeanMethod(methodMetadata, configClass));
}
public void addBeanMethod(BeanMethod method) {
this.beanMethods.add(method);
}
3）、将配置类中定义的bean注册到容器中
ConfigurationClassBeanDefinitionReader#loadBeanDefinitions(configClasses)
/**
* Read a particular {@link ConfigurationClass}, registering bean definitions
* for the class itself and all of its {@link Bean} methods.
*/
private void loadBeanDefinitionsForConfigurationClass(
ConfigurationClass configClass, TrackedConditionEvaluator trackedConditionEvaluator) {
if (trackedConditionEvaluator.shouldSkip(configClass)) {
String beanName = configClass.getBeanName();
if (StringUtils.hasLength(beanName) && this.registry.containsBeanDefinition(beanName)) {
this.registry.removeBeanDefinition(beanName);
}
this.importRegistry.removeImportingClass(configClass.getMetadata().getClassName());
return;
}
if (configClass.isImported()) {
registerBeanDefinitionForImportedConfigurationClass(configClass);
}
for (BeanMethod beanMethod : configClass.getBeanMethods()) {
loadBeanDefinitionsForBeanMethod(beanMethod);
}
loadBeanDefinitionsFromImportedResources(configClass.getImportedResources());
loadBeanDefinitionsFromRegistrars(configClass.getImportBeanDefinitionRegistrars());
}
四、总结–解析流程图
spring 在容器解析的时候会自动的注入ConfigurationClassPostProcessor 这个工厂后置处理器，该处理器会解析所有被@Configuration标注的配置类。其对应示例图如下：
