Spring随笔

BeanFactory和ApplictionContext

• BeanFactory装载了bean实例，一个容器，提供了对bean的增删改查

• ApplictionContext继承了factory，除此之外还装配了一系列的工厂后置处理器和bean后置处理器

  • BeanFactoryPostProcessor工厂的增强，比如解析@Config，@ComponentScan，@Bean等注解
  • BeanPostProcessor bean的增强，比如解析@Autowired，@Resource等

bean增强 AutowiredAnnotationBeanPostProcessor

        Field bean3 = Bean1.class.getDeclaredField("bean3");
        //对字段依赖的封装
        DependencyDescriptor dd1 = new DependencyDescriptor(bean3, false);
        Object o = beanFactory.doResolveDependency(dd1, null, null, null);
        System.out.println(o);

        Method setBean2 = Bean1.class.getDeclaredMethod("setBean2", Bean2.class);
        DependencyDescriptor dd2 =
        				//方法中可能会有多个参数
                new DependencyDescriptor(new MethodParameter(setBean2, 0), true);
                //交个bean工厂去解析依赖数据
        Object o1 = beanFactory.doResolveDependency(dd2, null, null, null);
        System.out.println(o1);

工厂增强 ComponentScanPostProcessor

public class ComponentScanPostProcessor implements BeanDefinitionRegistryPostProcessor {
    @Override // context.refresh
    public void postProcessBeanFactory(ConfigurableListableBeanFactory configurableListableBeanFactory) throws BeansException {

    }

    @Override
    public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry beanFactory) throws BeansException {
        try {
            ComponentScan componentScan = AnnotationUtils.findAnnotation(Config.class, ComponentScan.class);
            if (componentScan != null) {
                for (String p : componentScan.basePackages()) {
                    System.out.println(p);
                    // com.itheima.a05.component -> classpath*:com/itheima/a05/component/**/*.class
                    String path = "classpath*:" + p.replace(".", "/") + "/**/*.class";
                    System.out.println(path);
                    CachingMetadataReaderFactory factory = new CachingMetadataReaderFactory();
                    Resource[] resources = new PathMatchingResourcePatternResolver().getResources(path);
                    AnnotationBeanNameGenerator generator = new AnnotationBeanNameGenerator();
                    for (Resource resource : resources) {
                        // System.out.println(resource);
                        MetadataReader reader = factory.getMetadataReader(resource);
                        // System.out.println("类名:" + reader.getClassMetadata().getClassName());
                        AnnotationMetadata annotationMetadata = reader.getAnnotationMetadata();
                        // System.out.println("是否加了 @Component:" + annotationMetadata.hasAnnotation(Component.class.getName()));
                        // System.out.println("是否加了 @Component 派生:" + annotationMetadata.hasMetaAnnotation(Component.class.getName()));
                        if (annotationMetadata.hasAnnotation(Component.class.getName())
                            || annotationMetadata.hasMetaAnnotation(Component.class.getName())) {
                            AbstractBeanDefinition bd = BeanDefinitionBuilder
                                    .genericBeanDefinition(reader.getClassMetadata().getClassName())
                                    .getBeanDefinition();
                            String name = generator.generateBeanName(bd, beanFactory);
                            beanFactory.registerBeanDefinition(name, bd);
                        }
                    }
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}