使用Spring的BeanFactoryPostProcessor扩展点完成自定义注解扫描
一、概述
本次实验是上一次https://blog.csdn.net/2301_80749359/article/details/157651601?fromshare=blogdetail&sharetype=blogdetail&sharerId=157651601&sharerefer=PC&sharesource=2301_80749359&sharefrom=from_link的扩展，只是加了自定义注解较为方便。
二、具体步骤
2.1创建自定义注解
packagecom.itheima.ano;importjava.lang.annotation.ElementType;importjava.lang.annotation.Retention;importjava.lang.annotation.RetentionPolicy;importjava.lang.annotation.Target;//设定在哪些类型上可以使用@Target(ElementType.TYPE)//设定作用的范围@Retention(RetentionPolicy.RUNTIME)public@interfaceMyComponent{// 配置value属性，以代表bean的名字Stringvalue();}2.2引入扫描注解包的工具类
packagecom.itheima.utils;importcom.itheima.ano.MyComponent;importorg.springframework.core.io.Resource;importorg.springframework.core.io.support.PathMatchingResourcePatternResolver;importorg.springframework.core.io.support.ResourcePatternResolver;importorg.springframework.core.type.classreading.CachingMetadataReaderFactory;importorg.springframework.core.type.classreading.MetadataReader;importorg.springframework.core.type.classreading.MetadataReaderFactory;importorg.springframework.util.ClassUtils;importjava.lang.annotation.Annotation;importjava.util.HashMap;importjava.util.List;importjava.util.Map;publicclassBaseClassScanUtils{//设置资源规则privatestaticfinalStringRESOURCE_PATTERN="/**/*.class";publicstaticMap<String,Class>scanMyComponentAnnotation(StringbasePackage){//创建容器存储使用了指定注解的Bean字节码对象Map<String,Class>annotationClassMap=newHashMap<String,Class>();//spring工具类，可以获取指定路径下的全部类ResourcePatternResolverresourcePatternResolver=newPathMatchingResourcePatternResolver();try{Stringpattern=ResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX+ClassUtils.convertClassNameToResourcePath(basePackage)+RESOURCE_PATTERN;Resource[]resources=resourcePatternResolver.getResources(pattern);//MetadataReader 的工厂类MetadataReaderFactoryrefractory=newCachingMetadataReaderFactory(resourcePatternResolver);for(Resourceresource:resources){//用于读取类信息MetadataReaderreader=refractory.getMetadataReader(resource);//扫描到的classStringclassname=reader.getClassMetadata().getClassName();Class<?>clazz=Class.forName(classname);//判断是否属于指定的注解类型if(clazz.isAnnotationPresent(MyComponent.class)){//获得注解对象MyComponentannotation=clazz.getAnnotation(MyComponent.class);//获得属value属性值StringbeanName=annotation.value();//判断是否为""if(beanName!=null&&!beanName.equals("")){//存储到Map中去annotationClassMap.put(beanName,clazz);continue;}//如果没有为"",那就把当前类的类名作为beanNameannotationClassMap.put(clazz.getSimpleName(),clazz);}}}catch(Exceptionexception){}returnannotationClassMap;}publicstaticvoidmain(String[]args){Map<String,Class>stringClassMap=scanMyComponentAnnotation("com.itheima");System.out.println(stringClassMap);}}2.3利用工具类扫描包
利用工具类扫描包（包括该包及其子包下）中带有@MyComponent注释的类，然后遍历Map进行相关的操作（具体见代码注释）
packagecom.itheima.processor;importcom.itheima.utils.BaseClassScanUtils;importorg.springframework.beans.BeansException;importorg.springframework.beans.factory.config.BeanDefinition;importorg.springframework.beans.factory.config.ConfigurableListableBeanFactory;importorg.springframework.beans.factory.support.BeanDefinitionRegistry;importorg.springframework.beans.factory.support.BeanDefinitionRegistryPostProcessor;importorg.springframework.beans.factory.support.RootBeanDefinition;importjava.util.Map;publicclassMyComponentBeanFactoryPostProcessorimplementsBeanDefinitionRegistryPostProcessor{@OverridepublicvoidpostProcessBeanDefinitionRegistry(BeanDefinitionRegistrybeanDefinitionRegistry)throwsBeansException{//先是使用扫描的工具进行扫描Map<String,Class>myComponentAnnotationMap=BaseClassScanUtils.scanMyComponentAnnotation("com.itheima");// 然后是遍历这个map，得到bbeanDefinitionmyComponentAnnotationMap.forEach((beanName,beanClass)->{// 先是获取到全限制名(转为String类型的)StringclassName=beanClass.getName();// 然后是定义bbeanDefinitionBeanDefinitionbeanDefinition=newRootBeanDefinition();beanDefinition.setBeanClassName(className);// 再是进行注册，这就是放到单例池单中了beanDefinitionRegistry.registerBeanDefinition(beanName,beanDefinition);});}@OverridepublicvoidpostProcessBeanFactory(ConfigurableListableBeanFactoryconfigurableListableBeanFactory)throwsBeansException{}}2.4测试：
packagecom.itheima.test;importcom.alibaba.druid.pool.DruidDataSource;importcom.itheima.beans.OthrerBean;importcom.itheima.beans.Xxxbean;importcom.itheima.dao.impl.UserDaoImpl;importcom.itheima.dao.personDao;importcom.itheima.service.UserService;importcom.mysql.jdbc.Connection;importorg.apache.ibatis.io.Resources;importorg.apache.ibatis.session.SqlSession;importorg.apache.ibatis.session.SqlSessionFactory;importorg.apache.ibatis.session.SqlSessionFactoryBuilder;importorg.springframework.beans.factory.config.BeanDefinition;importorg.springframework.beans.factory.support.DefaultListableBeanFactory;importorg.springframework.beans.factory.xml.XmlBeanDefinitionReader;importorg.springframework.context.ApplicationContext;importorg.springframework.context.support.ClassPathXmlApplicationContext;importjavax.xml.bind.annotation.XmlAccessOrder;importjava.io.IOException;importjava.io.InputStream;importjava.sql.DriverManager;publicclassBeanFactoryTest{publicstaticvoidmain(String[]args)throwsException{ApplicationContextapplicationContext=newClassPathXmlApplicationContext("applicationContext_beanfac.xml");OthrerBeanothrerBean=(OthrerBean)applicationContext.getBean("otherBean");System.out.println(othrerBean);}}结果：
