springboot @import 说明

---

springboot @import 说明

 

@import：将导入的类注册为bean

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Import {
    Class<?>[] value();
}

 

 

**********************

直接注册为bean

 

@EnableScheduling：导入SchedulingConfiguration类，类上有注解@Configuration

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

 

SchedulingConfiguration

@Configuration
@Role(2)
public class SchedulingConfiguration {
    public SchedulingConfiguration() {
    }

    @Bean(
        name = {"org.springframework.context.annotation.internalScheduledAnnotationProcessor"}
    )
    @Role(2)
    public ScheduledAnnotationBeanPostProcessor scheduledAnnotationProcessor() {
        return new ScheduledAnnotationBeanPostProcessor();
    }
}

 

 

*******************

根据条件选择注册

 

@EnableAsync：导入类AsyncConfigurationSelector，该类实现了ImportSelector接口，根据条件选择注册的类

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Import({AsyncConfigurationSelector.class})
public @interface EnableAsync {
    Class<? extends Annotation> annotation() default Annotation.class;

    boolean proxyTargetClass() default false;

    AdviceMode mode() default AdviceMode.PROXY;

    int order() default 2147483647;
}

 

ImportSelector：根据条件选择注册的类

public interface ImportSelector {
    String[] selectImports(AnnotationMetadata var1);
}

 

AsyncConfigurationSelector

public class AsyncConfigurationSelector extends AdviceModeImportSelector<EnableAsync> {
    private static final String ASYNC_EXECUTION_ASPECT_CONFIGURATION_CLASS_NAME = "org.springframework.scheduling.aspectj.AspectJAsyncConfiguration";

    public AsyncConfigurationSelector() {
    }

    @Nullable
    public String[] selectImports(AdviceMode adviceMode) {
        switch(adviceMode) {
        case PROXY:
            return new String[]{ProxyAsyncConfiguration.class.getName()};
                   //如果为proxy，导入ProxyAsyncConfiguration类，默认导入该类
        case ASPECTJ:
            return new String[]{"org.springframework.scheduling.aspectj.AspectJAsyncConfiguration"};
                   //如果为aspectj，导入AspectJAsyncConfiguration类
        default:
            return null;
        }
    }
}

 

AdviceMode为Proxy导入的类

@Configuration
@Role(2)
public class ProxyAsyncConfiguration extends AbstractAsyncConfiguration {
    public ProxyAsyncConfiguration() {
    }

    @Bean(
        name = {"org.springframework.context.annotation.internalAsyncAnnotationProcessor"}
    )
    @Role(2)
    public AsyncAnnotationBeanPostProcessor asyncAdvisor() {
        Assert.notNull(this.enableAsync, "@EnableAsync annotation metadata was not injected");
        AsyncAnnotationBeanPostProcessor bpp = new AsyncAnnotationBeanPostProcessor();
        bpp.configure(this.executor, this.exceptionHandler);
        Class<? extends Annotation> customAsyncAnnotation = this.enableAsync.getClass("annotation");
        if (customAsyncAnnotation != AnnotationUtils.getDefaultValue(EnableAsync.class, "annotation")) {
            bpp.setAsyncAnnotationType(customAsyncAnnotation);
        }

        bpp.setProxyTargetClass(this.enableAsync.getBoolean("proxyTargetClass"));
        bpp.setOrder((Integer)this.enableAsync.getNumber("order"));
        return bpp;
    }
}

 

 

*******************

运行时注册类

 

@EnableAspectJAutoProxy：导入AspectJAutoProxyRegistratr类，该类实现ImportBeanDefinitionRegistratr接口，可在运行时注册bean

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Import({AspectJAutoProxyRegistrar.class})
public @interface EnableAspectJAutoProxy {
    boolean proxyTargetClass() default false;

    boolean exposeProxy() default false;
}

 

ImportBeanDefinitionRegistratr：运行时注册bean的接口

public interface ImportBeanDefinitionRegistrar {
    default void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry, BeanNameGenerator importBeanNameGenerator) {
        this.registerBeanDefinitions(importingClassMetadata, registry);
    }

    default void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
    }
}

 

AspectJAutoProxyRegistratr：导入的注册类

class AspectJAutoProxyRegistrar implements ImportBeanDefinitionRegistrar {
    AspectJAutoProxyRegistrar() {
    }

    public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
        AopConfigUtils.registerAspectJAnnotationAutoProxyCreatorIfNecessary(registry);
        AnnotationAttributes enableAspectJAutoProxy = AnnotationConfigUtils.attributesFor(importingClassMetadata, EnableAspectJAutoProxy.class);
        if (enableAspectJAutoProxy != null) {
            if (enableAspectJAutoProxy.getBoolean("proxyTargetClass")) {
                AopConfigUtils.forceAutoProxyCreatorToUseClassProxying(registry);
            }

            if (enableAspectJAutoProxy.getBoolean("exposeProxy")) {
                AopConfigUtils.forceAutoProxyCreatorToExposeProxy(registry);
            }
        }

    }
}

 

AopConfigUtils：aop配置工具类

public abstract class AopConfigUtils {

    public static void forceAutoProxyCreatorToUseClassProxying(BeanDefinitionRegistry registry) {
        if (registry.containsBeanDefinition("org.springframework.aop.config.internalAutoProxyCreator")) {
            BeanDefinition definition = registry.getBeanDefinition("org.springframework.aop.config.internalAutoProxyCreator");
            definition.getPropertyValues().add("proxyTargetClass", Boolean.TRUE);
        }

    }

    public static void forceAutoProxyCreatorToExposeProxy(BeanDefinitionRegistry registry) {
        if (registry.containsBeanDefinition("org.springframework.aop.config.internalAutoProxyCreator")) {
            BeanDefinition definition = registry.getBeanDefinition("org.springframework.aop.config.internalAutoProxyCreator");
            definition.getPropertyValues().add("exposeProxy", Boolean.TRUE);
        }

    }

    。。。。
}

 

 

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示例

 

*****************

pojo 层

 

Person

@Data
public class Person {

    private String name;
    private Integer age;
}

 

People

@Data
public class People {
    
    private String name;
    private Integer age;
}

 

Student

@Data
public class Student {
    
    private String name;
    private Integer age;
}

 

*****************

config 层

 

DataConfig

class CustomImportSelector implements ImportSelector {

    @Override
    public String[] selectImports(AnnotationMetadata annotationMetadata) {
        return new String[]{People.class.getName()};
    }
}

class CustomImportBeanDefinitionRegistrar implements ImportBeanDefinitionRegistrar{

    @Override
    public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
        BeanDefinition beanDefinition=new RootBeanDefinition(Student.class);
        beanDefinition.getPropertyValues().add("name","瓜田李下");
        beanDefinition.getPropertyValues().add("age",20);
        registry.registerBeanDefinition("student",beanDefinition);  //student为bean的名字
    }  //此种方式可自定义bean的属性
}

@Import({Person.class,CustomImportSelector.class,
        CustomImportBeanDefinitionRegistrar.class})
@Configuration
public class DataConfig {

}

 

*****************

controller 层

 

HelloController

@RestController
public class HelloController {

    @Resource
    private Person person;

    @Resource
    private People people;

    @Resource
    private Student student;

    @RequestMapping("/hello")
    public String hello(){
        System.out.println(person);
        System.out.println(people);
        System.out.println(student);

        return "success";
    }
}

 

 

**********************

控制台输出

 

localhost:8080/hello

Person(name=null, age=null)
People(name=null, age=null)
Student(name=瓜田李下, age=20)