SpringBoot如何将@Bean方法注册为BeanDefinition
我们以MyBATisPlusAutoConfiguration为例说明sqlSessionFactory()这个方法如何解析为BeanDefinition。
@Bean
@ConditionalOnMissingBean
public SqlSessionFactory sqlSessionFactory(DataSource dataSource) throws Exception {
//...
}
这个解析过程是在ConfigurationClassBeanDefinitionReader的loadBeanDefinitionsForBeanMethod方法。
private void loadBeanDefinitionsForBeanMethod(BeanMethod beanMethod) {
ConfigurationClass configClass = beanMethod.getConfigurationClass();
MethodMetadata metadata = beanMethod.getMetadata();
//本文这里是sqlSessionFactory
String methodName = metadata.getMethodName();
// Do we need to mark the bean as skipped by its condition?
//判断是否需要跳过
if (this.conditionEvaLuator.shouldSkip(metadata, ConfigurationPhase.REGISTER_BEAN)) {
configClass.skippedBeanMethods.add(methodName);
return;
}
//判断是否需要跳过
if (configClass.skippedBeanMethods.contains(methodName)) {
return;
}
//获取到@Bpythonean的注解信息
AnnotationAttributes bean = AnnotationConfigUtils.attributesFor(metadata, Bean.class);
Assert.state(bean != null, "No @Bean annotation attributes");
// Consider name and any aliases
List<String> names = new ArrayList<>(Arrays.asList(bean.getStringArray("name")));
//尝试获取bean的名称，默认使用methodName
String beanName = (!names.isEmpty() ? names.remove(0) : methodName);
// Register aliases even when overridden
//尝试注册别名
for (String alias : names) {
this.registry.registerAlias(beanName, alias);
}
// Has this effectively been overridden before (e.g. via XML)?
//校验BeanDefinition是否存在、是否允许覆盖
if (isOverriddenByExistingDefinition(beanMethod, beanName)) {
if (beanName.equals(beanMethod.getConfigurationClass().getBeanName())) {
throw new BeanDefinitionStoreException(beanMethod.getConfigurationClass().getResource().getDescription(),
beanName, "Bean name derived from @Bean method '" + beanMethod.getMetadata().getMethodName() +
"' clashes with bean name for containing configuration class; please make those names unique!");
}
return;
}
//得到一个ConfigurationClassBeanDefinition
ConfigurationClassBeanDefinition beanDef = new ConfigurationClassBeanDefinition(configClass, metadata);
beanDef.setResource(configClass.getResource());
beanDef.setSource(this.sourceExtractor.extractSource(metadata, configClass.getResource()));
//方法是否为静态方法
if (metadata.isStatic()) {
// static @Bean method
if (configClass.getMetadata() instanceof StandardAnnotationMet编程adata) {
beanDef.setBeanClass(((StandardAnnotationMetadata) configClass.getMetadata()).getIntrospectedClass());
}
else {
beanDef.setBeanClassName(configClass.getMetadata().getClassName());
}
beanDef.setUniqueFactoryMethodName(methodName);
}
elsejavascript {
//实例方法，非静态方法
// instance @Bean method
//设置FactoryBeanName，本文这里是
//com.baomidou.mybatisplus.autoconfigure.MybatisPlusAutoConf编程客栈iguration
beanDef.setFactoryBeanName(configClass.getBeanName());
// 设置factoryMethodName 本文这里是sqlSessionFactory
beanDef.setUniqueFactoryMethodName(methodName);
}
//本文这里跳过 这里是SimpleMethodMetadata
if (metadata instanceof StandardMethodMetadata) {
beanDef.setResolvedFactoryMethod(((StandardMethodMetadata) metadata).getIntrospectedMethod());
}
//设置注入标识 AUTOWIRE_CONSTRUCTOR=3
beanDef.setAutowireMode(AbstractBeanDefinition.AUTOWIRE_CONSTRUCTOR);
//设置SKIP_REQUIRED_CHECK_ATTRIBUTE属性
beanDef.setAttribute(org.springframework.beans.factory.annotation.RequiredAnnotationBeanPostProcessor.
SKIP_REQUIRED_CHECK_ATTRIBUTE, Boolean.TRUE);
//BeanDefinition的通用后置处理，如Lazy、Primary、DependsOn、Role以及Description
AnnotationConfigUtils.processCommonDefinitionAnnotations(beanDef, metadata);
//解析注解上配置的autowire
Autowire autowire = bean.getEnum("autowire");
if (autowire.isAutowire()) {
beanDef.setAutowireMode(autowire.value());
}
//解析注解上配置的autowireCandidate
boolean autowireCandidate = bean.getBoolean("autowireCandidate");
if (!autowireCandidate) {
beanDef.setAutowireCandidate(false);
}
//解析注解上配置的initMethod
String initMethodName = bean.getString("initMethod");
if (StringUtils.hasText(initMethodName)) {
beanDef.setInitMethodName(initMethodName);
}
//解析注解上配置的destroyMethod
String destroyMethodName = bean.getString("destroyMethod");
beanDef.setDestroyMethodName(destroyMethodName);
// Consider scoping
ScopedProxyMode proxyMode = ScopedProxyMode.NO;
//获取@Scope注解信息
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
BeanDefinition beanDefToRegister = beanDef;
if (proxyMode != ScopedProxyMode.NO) {
//尝试创建代理
BeanDefinitionHolder proxyDef = ScopedProxyCreator.createScopedProxy(
new BeanDefinitionHolder(beanDef, beanName), this.registry,
proxyMode == ScopedProxyMode.TARGET_CLASS);
beanDefToRegister = new ConfigurationClassBeanDefinition(
(RootBeanDefinition) proxyDef.getBeanDefinition(), configClass, metadata);
}
if (logger.isTraceEnabled()) {
logger.trace(String.format("Registering bean definition for @Bean method %s.%s()",
configClass.getMetadata().getClassName(), beanName));
}
//注册BeanDefinition，beanName默认是methodName sqlSessionFactory
this.registry.registerBeanDefinition(beanName, beanDefToRegister);
}
方法流程如上所示，核心步骤都加了注释。这里要特别注意的是如下几点：
- 得到的BeanDefinition是ConfigurationClassBeanDefinition类型；
- 会为BeanDefinition设置factoryMethodName，这意味着当实例化这个bean的时候将采用工厂方法；
- 会区分方法是否为静态方法来设置BeanClass或者FactoryBeanName
这里得到的configClass
这里得到的MethodMetadata
最终得到的BeanDefinition属性
annotationMetadata = {SimpleAnnotationMetadata@5352}
factoryMethodMetadata = {SimpleMethodMetadata@5635}
decoratedDefinition = null
qualifiedElement = null
stale = false
allowCaching = true
isFactoryMethodUnique = true
targetType = null
resolvedTargetType = null
isFactoryBean = null
factoryMethodReturnType = null
factoryMethodToIntrospect = null
constructorArgumentLock = {Object@5823}
resolvedConstructorOrFactoryMethod = null
constructorArgumentsResolved = false
resolvedConstructorArguments = null
preparedConstructorArguments = null
postProcessingLock = {Object@5824}
postProcessed = false
beforeInstantiationResolved = null
externallyManagedConfigMembers = null
externallyManagedInitMethods = null
externallyManagedDestroyMethods = null
beanClass = null
scope = ""
abstractFlag = false
lazyInit = null
autowireMode = 3
dependencyCheck = 0
dependsOn = null
autowireCandidate = true
primary = false
qualifiers = {LinkedHashMap@5825} size = 0
instanceSupplier = null
nonPublicAccessAllowed = true
lenientConstructorResolution = false
factoryBeanName = "com.baomidou.mybatisplus.autoconfigure.MybatisPlusAutoConfiguration"
factoryMethodName = "sqlSessionFactory"
constructorArgumentValues = null
propertyValues = null
methodOverrides = {MethodOverrides@5826}
iniandroidtMethodName = null
destroyMethodName = "(inferred)"
enforceInitMethod = true
enforceDestroyMethod = true
synthetic = false
role = 0
description = null
resource = {ClassPathResource@5353} "class path resource [com/baomidou/mybatisplus/autoconfigure/MybatisPlusAutoConfiguration.class]"
source = {SimpleMethodMetadata@5635}
attributes = {LinkedHashMap@5827} size = 1
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