spring解析配置类
spring是如何判断一个类是否是配置类
配置类是如何注册成bd的
AnnotatedGenericBeanDefinition 配置类bd
public AnnotationConfigApplicationContext(Class<?>... componentClasses) {
// 1. 创建BeanFactory
// 2. 生成AnnotatedBeanDefinitionReader
// 3. 生成ClassPathBeanDefinitionScanner
this();
// 利用reader把componentClasses注册为一个BeanDefinition
register(componentClasses);
register(componentClasses); 把一个配置类解析成bd并注册到bean容器中
如何判断一个类是否是配置类
// 注意，并不是没有Configuration注解当前BeanDefinition就不是一个配置类
// 注意isConfigurationCandidate方法，会检查是否存在@Component， @ComponentScan，@Import，@ImportResource，@Bean注解
else if (config != null || isConfigurationCandidate(metadata)) {
beanDef.setAttribute(CONFIGURATION_CLASS_ATTRIBUTE, CONFIGURATION_CLASS_LITE);
}
isConfigurationCandidate 的方法如下:
private static final Set<String> candidateIndicators = new HashSet<>(8);
static {
candidateIndicators.add(Component.class.getName());
candidateIndicators.add(ComponentScan.class.getName());
candidateIndicators.add(Import.class.getName());
candidateIndicators.add(ImportResource.class.getName());
}
public static boolean isConfigurationCandidate(AnnotationMetadata metadata) {
// Do not consider an interface or an annotation...
if (metadata.isInterface()) {
return false;
}
// Any of the typical annotations found?
// candidateIndicators
for (String indicator : candidateIndicators) {
if (metadata.isAnnotated(indicator)) {
return true;
}
}
// Finally, let's look for @Bean methods...
try {
return metadata.hasAnnotatedMethods(Bean.class.getName());
}
catch (Throwable ex) {
if (logger.isDebugEnabled()) {
logger.debug("Failed to introspect @Bean methods on class [" + metadata.getClassName() + "]: " + ex);
}
return false;
}
}
通过上述方法判断一个类是否是配置类
找到配置类开始解析
public void parse(Set<BeanDefinitionHolder> configCandidates) {
// 遍历多个配置类的BeanDefinition
for (BeanDefinitionHolder holder : configCandidates) {
BeanDefinition bd = holder.getBeanDefinition();
try {
// 处理有注解的BeanDefinition
if (bd instanceof AnnotatedBeanDefinition) {
// 处理注解的信息
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);
}
}
this.deferredImportSelectorHandler.process();
}
protected final void parse(AnnotationMetadata metadata, String beanName) throws IOException {
// ConfigurationClass表示配置类信息，包括配置上的注解信息，和beanName，以及还有一个resource属性，表示配置类的类路径
processConfigurationClass(new ConfigurationClass(metadata, beanName));
}
// 解析配置类
protected void processConfigurationClass(ConfigurationClass configClass) throws IOException {
// 解析@Conditional注解，判断是否需要解析
if (this.conditionEvaluator.shouldSkip(configClass.getMetadata(), ConfigurationPhase.PARSE_CONFIGURATION)) {
return;
}
ConfigurationClass existingClass = this.configurationClasses.get(configClass);
if (existingClass != null) {
if (configClass.isImported()) {
if (existingClass.isImported()) {
// todo
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);
this.knownSuperclasses.values().removeIf(configClass::equals);
}
}
// Recursively process the configuration class and its superclass hierarchy.
SourceClass sourceClass = asSourceClass(configClass);
do {
sourceClass = doProcessConfigurationClass(configClass, sourceClass);
}
while (sourceClass != null);
// 把当前配置类存在configurationClasses里面
this.configurationClasses.put(configClass, configClass);
}
@Nullable
protected final SourceClass doProcessConfigurationClass(ConfigurationClass configClass, SourceClass sourceClass)
throws IOException {
// 1. 如果配置bean上有@Component注解，递归去解析内部类上的注解
if (configClass.getMetadata().isAnnotated(Component.class.getName())) {
// Recursively process any member (nested) classes first
processMemberClasses(configClass, sourceClass);
}
// Process any @PropertySource annotations
// 2. 解析@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");
}
}
// Process any @ComponentScan annotations
// 3. 解析@ComponentScan注解，并进行扫描
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
// 扫描得到BeanDefinition
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();
}
// 检查扫描所得到BeanDefinition是不是配置Bean，基本上都有@Component注解，所以都是配置类
if (ConfigurationClassUtils.checkConfigurationClassCandidate(bdCand, this.metadataReaderFactory)) {
parse(bdCand.getBeanClassName(), holder.getBeanName());
}
}
}
}
// Process any @Import annotations
// 4. 解析@Import，getImports方法返回AppConfig.class上定义的Import注解中所导入的类的信息
processImports(configClass, sourceClass, getImports(sourceClass), true);
// Process any @ImportResource annotations
// 5. 解析@ImportResource，得到导入进来的spring的xml配置文件，然后解析
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);
}
}
// Process individual @Bean methods
// 6. 解析配置类中的加了@Bean注解的方法
Set<MethodMetadata> beanMethods = retrieveBeanMethodMetadata(sourceClass);
for (MethodMetadata methodMetadata : beanMethods) {
configClass.addBeanMethod(new BeanMethod(methodMetadata, configClass));
}
// Process default methods on interfaces
// 7. 如果配置类实现了某个接口，那么则解析该接口中的加了@Bean注解的默认方法
processInterfaces(configClass, sourceClass);
// Process superclass, if any
// 8. 如果有父类，则返回父类给上层遍历进行处理
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;
}
1.处理@ComponentScan注解 (主要是通过这个注解注入大多数的业务bean)
protected Set<BeanDefinitionHolder> doScan(String... basePackages) {
// 这是Spring中的Assert，大家开发时也可以用
Assert.notEmpty(basePackages, "At least one base package must be specified");
Set<BeanDefinitionHolder> beanDefinitions = new LinkedHashSet<>();
for (String basePackage : basePackages) {
// 扫描包路径得到BeanDefinition，得到的BeanDefinition是空的，还没有解析类上所定义的注解信息
Set<BeanDefinition> candidates = findCandidateComponents(basePackage);
for (BeanDefinition candidate : candidates) {
// 得到Scope的信息，并设置
ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(candidate);
candidate.setScope(scopeMetadata.getScopeName());
// 得到beanName
String beanName = this.beanNameGenerator.generateBeanName(candidate, this.registry);
if (candidate instanceof AbstractBeanDefinition) {
// 扫描出来的bd设置默认值，进一步填充bd中的属性
postProcessBeanDefinition((AbstractBeanDefinition) candidate, beanName);
}
if (candidate instanceof AnnotatedBeanDefinition) {
AnnotationConfigUtils.processCommonDefinitionAnnotations((AnnotatedBeanDefinition) candidate);
}
if (checkCandidate(beanName, candidate)) {
// 生成BeanDefinitionHolder并注册到registry中
BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(candidate, beanName);
definitionHolder =
AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
beanDefinitions.add(definitionHolder);
registerBeanDefinition(definitionHolder, this.registry);
}
}
}
return beanDefinitions;
}
扫描出了包添加的bd对象
说明方法是在Set candidates = findCandidateComponents(basePackage); 这里把包下面的java对象扫描进来
扫描的bd封装成ScannedGenericBeanDefinition
/**
* Scan the class path for candidate components.
* @param basePackage the package to check for annotated classes
* @return a corresponding Set of autodetected bean definitions
*/
public Set<BeanDefinition> findCandidateComponents(String basePackage) {
// 扫描Component，最笨的方法就是扫描basePackage下的所有类，看是否有@Component注解
// Spring提供了一种支持更快速扫描的机制，就是编译时直接创建一个静态的
if (this.componentsIndex != null && indexSupportsIncludeFilters()) {
return addCandidateComponentsFromIndex(this.componentsIndex, basePackage);
}
else {
// 得到所有的bd
return scanCandidateComponents(basePackage);
}
}
private Set<BeanDefinition> scanCandidateComponents(String basePackage) {
// 扫描类，得到BeanDefinition
Set<BeanDefinition> candidates = new LinkedHashSet<>();
try {
// 拼接成这种形式：classpath*:
String packageSearchPath = ResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX +
resolveBasePackage(basePackage) + '/' + this.resourcePattern;
// 获取到所有的class文件封装而成的Resource对象
Resource[] resources = getResourcePatternResolver().getResources(packageSearchPath);
boolean traceEnabled = logger.isTraceEnabled();
boolean debugEnabled = logger.isDebugEnabled();
for (Resource resource : resources) {
if (traceEnabled) {
logger.trace("Scanning " + resource);
}
if (resource.isReadable()) {
try {
// MetadataReader包含了对应class的元信息以及注解元信息, MetadataReader
MetadataReader metadataReader = getMetadataReaderFactory().getMetadataReader(resource);
// 判断一个类是不是Component
if (isCandidateComponent(metadataReader)) {
// 通过扫描@Component得到的BeanDefinition为ScannedGenericBeanDefinition
ScannedGenericBeanDefinition sbd = new ScannedGenericBeanDefinition(metadataReader);
sbd.setResource(resource);
sbd.setSource(resource);
// 再进一步验证是不是备选的Component
if (isCandidateComponent(sbd)) {
if (debugEnabled) {
logger.debug("Identified candidate component class: " + resource);
}
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;
}
这些resource 是如何得到的 大致是遍历com.luban 下所有文件 得到的