title: Spring 框架源碼解讀13
date: 2020/04/20 16:51

本節(jié)內容 & 思考題

@ComponentScan 注解

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點進去 parse 方法看看：

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開始吧

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
public @interface ComponentScan {

    /**
     * 掃描的包
     */
    String[] value();
}


private void processConfigurationClass(BeanDefinitionRegistry registry, BeanDefinition classBeanDefinition, Class<?> clazz) {
    ...

    // 4长踊、處理 @ComponentScan 注解
    ComponentScan componentScan = AnnotationUtil.getAnnotation(clazz, ComponentScan.class);
    if (ObjectUtil.isNotEmpty(componentScan) && ObjectUtil.isNotEmpty(componentScan.value())) {

        // 掃描包并加入 bdMap 中
        List<BeanDefinition> beanDefinitions = this.processComponentScan(registry, componentScan.value());

        // 處理掃描到的類上包含 @Configuration 的，對他進行解析
        for (BeanDefinition beanDefinition : beanDefinitions) {
            // 找到類上攜帶 @Configuration 的
            Class<?> childClazz = ReflectUtils.getType(beanDefinition.getClassName());
            Configuration configuration = AnnotationUtil.getAnnotation(childClazz, Configuration.class);
            if (ObjectUtil.isNotEmpty(configuration)) {
                // 處理 @Configuration 標注的類
                this.processConfigurationClass(registry, beanDefinition, childClazz);
            }
        }
    }
    ...
}

private List<BeanDefinition> processComponentScan(BeanDefinitionRegistry registry, String[] basePackages) {
    List<BeanDefinition> beanDefinitions = new ArrayList<>();

    for (String basePackage : basePackages) {
        Set<Class<?>> classes = ClassUtil.scanPackage(basePackage);
        for (Class<?> clazz : classes) {
            // 判斷是否具有 @Component 注解嚼松，并且本身不是注解
            Component component = AnnotationUtil.getAnnotation(clazz, Component.class);
            if (ObjectUtil.isNotNull(component) && !clazz.isAnnotation()) {
                DefaultBeanDefinition bd = new DefaultBeanDefinition();

                String beanName = StrUtil.isNotBlank(component.value()) ? component.value() : StrUtil.lowerFirst(clazz.getSimpleName());
                bd.setName(beanName);
                bd.setClassName(clazz.getName());
                registry.registerBeanDefinition(beanName, bd);
                beanDefinitions.add(bd);
            }
        }
    }

    return beanDefinitions;
}