spring自动装配bean的3种方式

spring boot：2.0.3

jdk：1.8

自动创建bean即大家常见的这样的注解。 @EnableWebMvc @EnableCacheing 等等

具体实现方式有3种。

方式1：使用@Import + @Configuration 组合

@Configuration
public class HelloConfiguration {

    @Bean
    public HelloBean helloBean() {
        return new HelloBean();
    }
}

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Import(HelloConfiguration.class)
public @interface EnableHelloWithConfiguration {
}

方式2：使用@Import + ImportSelect实现类 的组合

public class HelloSelector implements ImportSelector {

    @Override
    public String[] selectImports(AnnotationMetadata importingClassMetadata) {
        ObjectMapper om = new ObjectMapper();
        try {
            System.out.println("importingClassMetadata..." + om.writeValueAsString(importingClassMetadata));
        } catch (JsonProcessingException e) {
            e.printStackTrace();
        }
        return new String[]{
            HelloBean.class.getName()};
    }
}

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Import(HelloSelector.class)
public @interface EnableHelloWithSelector {
}

方式3：使用@Import + ImportBeanDefinitionRegistrar 实现类的方式

/**
 * 同时可以继承 ResourceLoaderAware, BeanFactoryAware 等获取其他信息
 */
public class HellobeanRegistry implements ImportBeanDefinitionRegistrar {

    @Override
    public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
        ObjectMapper om = new ObjectMapper();
        try {
            System.out.println("importingClassMetadata..." + om.writeValueAsString(importingClassMetadata));
        } catch (JsonProcessingException e) {
            e.printStackTrace();
        }
        ClassPathBeanDefinitionScanner scanner = new ClassPathBeanDefinitionScanner(registry, false);

        //方式一 直接使用对应的Bean.class 过滤
        TypeFilter helloServiceFilter = new AssignableTypeFilter(HelloBean.class);
        scanner.addIncludeFilter(helloServiceFilter);

        //方式二  使用注解过滤，即在目标bean上添加特定的注解
//        scanner.addIncludeFilter(new AnnotationTypeFilter(HelloBeanAnnotation.class));

        scanner.scan("com.illegalaccess.tutorials.spring.enable");
    }
}

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Import(HellobeanRegistry.class)
public @interface EnableHelloWithRegistry {
}

完整代码建：