深度解析@Configuration注解
aop和cglib
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;@Configuration
public class AppConfig {/**
cglib重写方法
/@Beanpublic A a() {return new A();}/**
cglib重写方法
/@Bean
public B b() {
/**
调用cglib重写的a方法
/return new B(a());
}
}
使用 enhancer 对 configClass 进行增强处理，得到增强后的类 enhancedClass。
如果 enhancedClass 与 configClass 不同，意味着类被增强，将用增强后的类替换原有类。
beanDef.setBeanClass(enhancedClass);// 在beanDefinition替换掉class
public void enhanceConfigurationClasses(ConfigurableListableBeanFactory beanFactory) {.....// 如果指定属性是full, 则进行下面处理，该属性在前面阶段设置if (ConfigurationClassUtils.CONFIGURATION_CLASS_FULL.equals(configClassAttr)) {if (!(beanDef instanceof AbstractBeanDefinition)) {throw new BeanDefinitionStoreException("Cannot enhance @Configuration bean definition '" +beanName + "' since it is not stored in an AbstractBeanDefinition subclass");}else if (logger.isInfoEnabled() && beanFactory.containsSingleton(beanName)) {logger.info("Cannot enhance @Configuration bean definition '" + beanName +"' since its singleton instance has been created too early. The typical cause " +"is a non-static @Bean method with a BeanDefinitionRegistryPostProcessor " +"return type: Consider declaring such methods as 'static'.");}// 加入到增强集合中configBeanDefs.put(beanName, (AbstractBeanDefinition) beanDef);}}if (configBeanDefs.isEmpty() || NativeDetector.inNativeImage()) {// nothing to enhance -> return immediatelyenhanceConfigClasses.end();return;}// 新建增强器ConfigurationClassEnhancer enhancer = new ConfigurationClassEnhancer();// 遍历待增强的容器列表for (Map.Entry<String, AbstractBeanDefinition> entry : configBeanDefs.entrySet()) {AbstractBeanDefinition beanDef = entry.getValue();// If a @Configuration class gets proxied, always proxy the target classbeanDef.setAttribute(AutoProxyUtils.PRESERVE_TARGET_CLASS_ATTRIBUTE, Boolean.TRUE);// Set enhanced subclass of the user-specified bean classClass<?> configClass = beanDef.getBeanClass();// 进行增强处理Class<?> enhancedClass = enhancer.enhance(configClass, this.beanClassLoader);if (configClass != enhancedClass) {if (logger.isTraceEnabled()) {logger.trace(String.format("Replacing bean definition '%s' existing class '%s' with " +"enhanced class '%s'", entry.getKey(), configClass.getName(), enhancedClass.getName()));}beanDef.setBeanClass(enhancedClass);}}enhanceConfigClasses.tag("classCount", () -> String.valueOf(configBeanDefs.keySet().size())).end();}
