自定义注解实现Spring容器注入Bean方式(类似于mybatis的@MapperScans)

 <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>

package com.whut.scaner.annotation;

import java.lang.annotation.*;

@Documented
@Inherited
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
public @interface MyService {
}

@Documented
@Inherited
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
public @interface MyServiceScans {
    String[] basePackages() default {};
}

package com.whut.scaner.config;

import com.whut.scaner.annotation.MyService;
import org.springframework.beans.factory.config.BeanDefinitionHolder;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.context.annotation.ClassPathBeanDefinitionScanner;
import org.springframework.core.type.filter.AnnotationTypeFilter;

import java.util.Set;

public class MyServiceClassPathBeanDefinitionScanner extends ClassPathBeanDefinitionScanner {
    public MyServiceClassPathBeanDefinitionScanner(BeanDefinitionRegistry registry, boolean useDefaultFilters) {
        super(registry, useDefaultFilters);
    }

    /**
     * @addIncludeFilter 将自定义的注解添加到扫描任务中
     */
    protected void registerFilters() {
        /**
         *  注入@MyService注解标记的类
         */
        addIncludeFilter(new AnnotationTypeFilter(MyService.class));
    }
    
    @Override
    protected Set<BeanDefinitionHolder> doScan(String... basePackages) {
        return super.doScan(basePackages);
    }
}

package com.whut.scaner.config;

import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.ImportBeanDefinitionRegistrar;
import org.springframework.core.type.AnnotationMetadata;

@Slf4j
public class MyServiceRegister implements ImportBeanDefinitionRegistrar {
    /**
     * 方法1： 将带有@MyService注解的类注入到Spring容器
     */
    @Override
    public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
        //自定义的扫描类MyClassPathBeanDefinitionScanner, 实现了ClassPathBeanDefinitionScanner接口
        // 当前MyClassPathBeanDefinitionScanner已被修改为扫描带有指定注解的类
        MyServiceClassPathBeanDefinitionScanner scanner = new MyServiceClassPathBeanDefinitionScanner(registry, false);
        scanner.registerFilters(); // 过滤带有注解的类并注入到容器中
        scanner.doScan("com.whut.scaner");
    }
}

package com.whut.scaner.config;

import com.whut.scaner.annotation.MyServiceScans;
import com.whut.scaner.filter.MyServicePackageFilter;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.context.annotation.ImportBeanDefinitionRegistrar;
import org.springframework.core.annotation.AnnotationAttributes;
import org.springframework.core.type.AnnotationMetadata;
import org.springframework.lang.NonNull;
import org.springframework.util.StringUtils;
import java.util.ArrayList;
import java.util.List;

@Slf4j
public class MyServiceScansRegister implements ImportBeanDefinitionRegistrar {

    @Override
    public void registerBeanDefinitions(AnnotationMetadata annotationMetadata
            , @NonNull BeanDefinitionRegistry beanDefinitionRegistry) {
        AnnotationAttributes annotationAttrs = AnnotationAttributes
                .fromMap(annotationMetadata.getAnnotationAttributes(MyServiceScans.class.getName()));
        if (annotationAttrs == null) {
            log.warn("EsMapperScan not exist");
            return;
        }
        //构造扫描器，并将spring的beanDefinitionRegistry注入到扫描器内，方便将扫描出的BeanDefinition注入进入beanDefinitionRegistry
        MyServiceClassPathBeanDefinitionScanner scanner = new MyServiceClassPathBeanDefinitionScanner(beanDefinitionRegistry, false);

        List<String> basePackages = new ArrayList<>();
        for (String pkg : annotationAttrs.getStringArray("basePackages")) {
            if (StringUtils.hasText(pkg)) {
                basePackages.add(pkg);
            }
        }
            //添加相关过滤器（为了用户无感知，不过滤@MyService注解，直接处理basePackages下面的所有类）
        scanner.addIncludeFilter(new MyServicePackageFilter());
        //扫描并注入
        scanner.doScan(StringUtils.toStringArray(basePackages));
    }
}

package com.whut.scaner.filter;

import lombok.NonNull;
import org.springframework.core.type.classreading.MetadataReader;
import org.springframework.core.type.classreading.MetadataReaderFactory;
import org.springframework.core.type.filter.TypeFilter;

/**
 * 直接过滤 直接处理basePackages下面的所有类
 */
public class MyServicePackageFilter implements TypeFilter {
    @Override
    public boolean match(MetadataReader metadataReader, @NonNull MetadataReaderFactory metadataReaderFactory) {
//        为了用户无感知，不用过滤出带有@Myservice的类，直接处理basePackages下面的所有类
//        return metadataReader.getAnnotationMetadata()
//                .hasAnnotation("com.whut.scanner.service");
        return true;
    }
}

@Configuration
@Import({MyServiceRegister.class, MyServiceScansRegister.class})
@MyServiceScans(basePackages={"com.whut.scaner.service2"})
public class MyConfiguration {
}

package com.whut.scaner.service;

import com.whut.scaner.annotation.MyService;


@MyService
public class UserService {
    public void test() {
        System.out.println("我是UserService的test()方法");
    }
}

package com.whut.scaner.service2;

public class StudentService {
    public void test() {
        System.out.println("我是StudentService的test()方法");
    }
}

@SpringBootApplication
public class App 
{
    public static void main( String[] args )
    {
        ConfigurableApplicationContext context = SpringApplication.run(App.class, args);
        UserService userService = context.getBean(UserService.class);
        userService.test();

        StudentService studentService = context.getBean(StudentService.class);
        studentService.test();
    }
}