Spring 高级 工厂后处理器模拟实现组件扫描-模拟ComponentScan 进阶

一、自定义Bean 后处理器 Processor

package com.mangoubiubiu.show.a05.component;

import com.mangoubiubiu.show.a05.Config;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.beans.factory.support.AbstractBeanDefinition;
import org.springframework.beans.factory.support.BeanDefinitionBuilder;
import org.springframework.beans.factory.support.DefaultListableBeanFactory;
import org.springframework.context.annotation.AnnotationBeanNameGenerator;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.support.GenericApplicationContext;
import org.springframework.core.annotation.AnnotationUtils;
import org.springframework.core.io.Resource;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
import org.springframework.core.type.AnnotationMetadata;
import org.springframework.core.type.classreading.CachingMetadataReaderFactory;
import org.springframework.core.type.classreading.MetadataReader;
import org.springframework.stereotype.Component;

import java.io.IOException;

public class ComponentScanPostProcessor implements BeanFactoryPostProcessor {

    /**
     * context.refresh   初始化ApplicationContext的时候会回调这个方法
     * @param configurableListableBeanFactory
     * @throws BeansException
     */
    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory configurableListableBeanFactory) throws BeansException {

        try {

            //Spring工具类 读取类的源信息
            CachingMetadataReaderFactory factory = new CachingMetadataReaderFactory();
            //查找某个类上有没有加注解 第一个参数 某个类的类型  第二个参数 要找的注解
            ComponentScan componentScan = AnnotationUtils.findAnnotation(Config.class, ComponentScan.class);
            if(componentScan!=null){
                for (String p:componentScan.basePackages()) {
                    System.out.println("包名："+p);


                    AnnotationBeanNameGenerator generator = new AnnotationBeanNameGenerator();

                    //com.mangoubiubiu.show.a05.component
                    StringBuilder path = new StringBuilder();
                    path.append("classpath*:").append(p.replace(".","/")).append("/**/*.class");
                    System.out.println("拼接后的包名："+path.toString());
                    //读取路径下的文件
                    Resource[] resources = new PathMatchingResourcePatternResolver().getResources(path.toString());
                    for (Resource res:resources) {
                        System.out.println("读取到的文件信息为："+res);
                        MetadataReader reader = factory.getMetadataReader(res);
                        System.out.println("得到类信息："+ reader.getClassMetadata().getClassName());
                        AnnotationMetadata annotationMetadata = reader.getAnnotationMetadata();
                        System.out.println("是否加了Component注解"+ annotationMetadata.hasAnnotation(Component.class.getName()));
                        System.out.println("是否加了Component注解 派生"+ annotationMetadata.hasMetaAnnotation(Component.class.getName()));

                        if(annotationMetadata.hasAnnotation(Component.class.getName()) || annotationMetadata.hasMetaAnnotation(Component.class.getName())){
                            AbstractBeanDefinition beanDefinition = BeanDefinitionBuilder.genericBeanDefinition(reader.getClassMetadata().getClassName()).getBeanDefinition();

                            if (configurableListableBeanFactory instanceof DefaultListableBeanFactory  ) {
                                DefaultListableBeanFactory beanFactory = ((DefaultListableBeanFactory) configurableListableBeanFactory);
                                String beanName = generator.generateBeanName(beanDefinition, beanFactory);
                                beanFactory.registerBeanDefinition(beanName,beanDefinition);
                            }
                        }


                    }


                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

二、将ComponentScanPostProcessor 注入到容器里面

package com.mangoubiubiu.show.a05;

import com.mangoubiubiu.show.a05.component.ComponentScanPostProcessor;
import lombok.extern.slf4j.Slf4j;
import org.mybatis.spring.mapper.MapperScannerConfigurer;
import org.springframework.beans.factory.support.AbstractBeanDefinition;
import org.springframework.beans.factory.support.BeanDefinitionBuilder;
import org.springframework.beans.factory.support.BeanNameGenerator;
import org.springframework.beans.factory.support.DefaultListableBeanFactory;
import org.springframework.context.annotation.AnnotationBeanNameGenerator;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.ConfigurationClassPostProcessor;
import org.springframework.context.support.GenericApplicationContext;
import org.springframework.core.annotation.AnnotationUtils;
import org.springframework.core.io.Resource;
import org.springframework.core.type.AnnotationMetadata;
import org.springframework.core.type.classreading.CachingMetadataReaderFactory;
import org.springframework.core.type.classreading.MetadataReader;
import org.springframework.stereotype.Component;

import java.awt.*;
import java.io.IOException;

@Slf4j
public class A05Application {

    private MetadataReader reader;

    public static void main(String[] args) throws IOException {
        GenericApplicationContext context = new GenericApplicationContext();
        //将config注册到容器里面
        context.registerBean("config",Config.class);
        context.registerBean(ComponentScanPostProcessor.class);
//        context.registerBean(MapperScannerConfigurer.class,beanDefinition -> {
//            beanDefinition.getPropertyValues().add("basePackage","com.mangoubiubiu.show.a05.mapper");
//        });



        //初始化容器

        context.refresh();

        for (String name: context.getBeanDefinitionNames()) {
            System.out.println(name);
        }

        context.close();
    }



}

 

可以看到在Config类上面配了包扫描，指定包下标注了@Component或者@Controller的bean 被我们成功扫描进IOC容器里面。