spring import 注解分析

Author: huifer

README.md

@@ -48,6 +48,7 @@
 - [Spring messageSource](/docs/Spring/clazz/Spring-MessageSource.md)
 - [Spring 自定义属性解析器](/docs/Spring/clazz/Spring-Custom-attribute-resolver.md)
 - [Spring 排序工具](/docs/Spring/clazz/Spring-OrderUtils.md)
+- [Spring-import注解](/docs/Spring/clazz/Spring-Import.md)
 ### Spring5 新特性
 - [Spring5-spring.components解析](/docs/Spring/Spring5新特性/Spring-spring-components.md)
 

docs/Spring/clazz/Spring-Import.md

@@ -0,0 +1,98 @@
+# Spring Import 
+- Author: [HuiFer](https://github.com/huifer)
+- 源码阅读仓库: [SourceHot-spring](https://github.com/SourceHot/spring-framework-read)
+
+## 分析
+- org.springframework.context.annotation.Import
+```java
+@Target(ElementType.TYPE)
+@Retention(RetentionPolicy.RUNTIME)
+@Documented
+public @interface Import {
+
+    /**
+     * {@link Configuration @Configuration}, {@link ImportSelector},
+     * {@link ImportBeanDefinitionRegistrar}, or regular component classes to import.
+     *
+     * 需要导入的类
+     */
+    Class<?>[] value();
+}
+```
+### ImportBeanDefinitionRegistrar
+- 注册Import Bean 
+- `org.springframework.context.annotation.ImportBeanDefinitionRegistrar`
+```java
+public interface ImportBeanDefinitionRegistrar {
+
+    /**
+     * Register bean definitions as necessary based on the given annotation metadata of
+     * the importing {@code @Configuration} class.
+     * <p>Note that {@link BeanDefinitionRegistryPostProcessor} types may <em>not</em> be
+     * registered here, due to lifecycle constraints related to {@code @Configuration}
+     * class processing.
+     *
+     * 对import value属性的注册
+     * @param importingClassMetadata annotation metadata of the importing class
+     * @param registry               current bean definition registry
+     */
+    void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry);
+
+}
+```
+- 两个实现类
+    1. `org.springframework.context.annotation.AutoProxyRegistrar`
+    2. `org.springframework.context.annotation.AspectJAutoProxyRegistrar`
+
+#### AutoProxyRegistrar
+```java
+public class AutoProxyRegistrar implements ImportBeanDefinitionRegistrar {
+
+    private final Log logger = LogFactory.getLog(getClass());
+
+    /**
+     * 注册import bean定义
+     */
+    @Override
+    public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
+        boolean candidateFound = false;
+        // 获取注解
+        Set<String> annTypes = importingClassMetadata.getAnnotationTypes();
+        for (String annType : annTypes) {
+            // 注解属性
+            AnnotationAttributes candidate = AnnotationConfigUtils.attributesFor(importingClassMetadata, annType);
+            if (candidate == null) {
+                continue;
+            }
+            // 获取 mode 属性
+            Object mode = candidate.get("mode");
+            // 获取代理对象
+            Object proxyTargetClass = candidate.get("proxyTargetClass");
+            if (mode != null && proxyTargetClass != null && AdviceMode.class == mode.getClass() &&
+                    Boolean.class == proxyTargetClass.getClass()) {
+                candidateFound = true;
+                if (mode == AdviceMode.PROXY) {
+                    // 注册
+                    AopConfigUtils.registerAutoProxyCreatorIfNecessary(registry);
+                    if ((Boolean) proxyTargetClass) {
+                        AopConfigUtils.forceAutoProxyCreatorToUseClassProxying(registry);
+                        return;
+                    }
+                }
+            }
+        }
+        if (!candidateFound && logger.isInfoEnabled()) {
+            String name = getClass().getSimpleName();
+            logger.info(String.format("%s was imported but no annotations were found " +
+                    "having both 'mode' and 'proxyTargetClass' attributes of type " +
+                    "AdviceMode and boolean respectively. This means that auto proxy " +
+                    "creator registration and configuration may not have occurred as " +
+                    "intended, and components may not be proxied as expected. Check to " +
+                    "ensure that %s has been @Import'ed on the same class where these " +
+                    "annotations are declared; otherwise remove the import of %s " +
+                    "altogether.", name, name, name));
+        }
+    }
+
+}
+```