springboot @import 说明
@import:将类导入到项目中,spring ioc容器将相关类注册为bean
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Import {
Class<?>[] value();
}
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注册bean一般有三种方式
****************************
直接将类注册为bean
@EnableScheduling:该注解导入SchedulingConfiguration类,SchedulingConfiguration上有注解@Configuration
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Import({SchedulingConfiguration.class})
@Documented
public @interface EnableScheduling {
}
@Configuration
@Role(2)
public class SchedulingConfiguration {
public SchedulingConfiguration() {
}
@Bean(
name = {"org.springframework.context.annotation.internalScheduledAnnotationProcessor"}
)
@Role(2)
public ScheduledAnnotationBeanPostProcessor scheduledAnnotationProcessor() {
return new ScheduledAnnotationBeanPostProcessor();
}
}
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根据条件选择注册的类
@EnableAsync:导入类AsyncConfigurationSelector,该类实现了ImportSelector接口,该接口选择最终注册的类
@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接口:选择需注册的类
public interface ImportSelector {
String[] selectImports(AnnotationMetadata var1);
}
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;
}
}
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运行时自动注册类
@EnableAspectJAutoProxy:导入AspectJAutoProxyRegistratr类,该类实现ImportBeanDefinitionRegistratr接口,实现在运行时注册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);
}
}
。。。。
}