[spring] spring advanced topics -@Enable ***How annotations work

Familiar with memory 2021-01-21 10:40:18
spring spring advanced topics enable


Reprint please indicate the source :http://blog.csdn.net/qq_26525215 This article comes from College trip _ The blog of memory

@EnableAspectJAutoProxy

@EnableAspectJAutoProxy annotation Activate Aspect Automatic agent

 <aop:aspectj-autoproxy/>

Open to AspectJ Auto agent support .

In the use of AOP When using the automatic agent of , If you understand Java Dynamic proxy for , It's easy to get familiar with AOP Automatic proxy of .

@EnableAsync

@EnableAsync Annotations enable support for asynchronous methods . I believe everyone is familiar with this . Asynchronous should be understood . Not very familiar , You can see this blog :- There are examples 【Spring】Spring Advanced topics - Multithreading -TaskExecutor

@EnableScheduling

@EnableScheduling Notes enable support for scheduled tasks .

It means literally , Enable support for scheduled tasks ! Generally @Scheduled The coordination of annotations .

See this blog for details : 【Spring】Spring Advanced topics - Planning tasks -@EnableScheduling

@EnableWebMVC

@EnableWebMVC Annotations are used to open Web MVC Configuration support for .

That is to say Spring MVC It's going to be used .

@EnableConfigurationProperties

@EnableConfigurationProperties Annotations are used to turn on @ConfigurationProperties Annotation configuration Bean Support for .

That is to say @EnableConfigurationProperties Annotations tell Spring Boot Enable to support @ConfigurationProperties

@EnableJpaRepositories

@EnableJpaRepositories Comment on Spring Data JPA Repostory Support for .

Spring Data JPA frame , The main aim is Spring The only business logic code not simplified to , thus , Developers save the only work left to implement the business logic of the persistence layer , The only thing to do , Just declare the interface of the persistence layer , Everything else Spring Data JPA To help you !

To put it simply ,Spring Data JPA It's a framework for persisting data .

@EnableTransactionManagement

@EnableTransactionManagement Annotations enable support for annotated transactions .

annotation @EnableTransactionManagement notice Spring,@Transactional Annotated classes are surrounded by facets of transactions . such @Transactional You can use it .

@EnableCaching

@EnableCaching Annotations enable annotated caching support

Through these simple @Enable* You can turn on support for a feature , So as to avoid configuring a lot of code , It greatly reduces the difficulty of use .

Let's take a look at these @Enable* Annotated source code , You can see that all annotations have one @Import annotation .

@Import Annotations are used to import configuration classes , That is to say, the implementation of automatic opening actually imports some automatic configuration Bean.

These import configuration methods are mainly divided into the following three types .

@Import There are three types of annotation import configuration

The first category : Import configuration class directly

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//
package org.springframework.scheduling.annotation;
import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import org.springframework.context.annotation.Import;
import org.springframework.scheduling.annotation.SchedulingConfiguration;
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Import({SchedulingConfiguration.class})
@Documented
public @interface EnableScheduling {
}

Import configuration class directly SchedulingConfiguration, This class annotates @Configuration, And registered a scheduledAnnotationProcessor Of Bean, Source code is as follows :

/*
* Copyright 2002-2015 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.scheduling.annotation;
import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Role;
import org.springframework.scheduling.config.TaskManagementConfigUtils;
/**
* {@code @Configuration} class that registers a {@link ScheduledAnnotationBeanPostProcessor}
* bean capable of processing Spring's @{@link Scheduled} annotation.
*
* <p>This configuration class is automatically imported when using the
* @{@link EnableScheduling} annotation. See {@code @EnableScheduling}'s javadoc
* for complete usage details.
*
* @author Chris Beams
* @since 3.1
* @see EnableScheduling
* @see ScheduledAnnotationBeanPostProcessor
*/
@Configuration
@Role(BeanDefinition.ROLE_INFRASTRUCTURE)
public class SchedulingConfiguration {
@Bean(name = TaskManagementConfigUtils.SCHEDULED_ANNOTATION_PROCESSOR_BEAN_NAME)
@Role(BeanDefinition.ROLE_INFRASTRUCTURE)
public ScheduledAnnotationBeanPostProcessor scheduledAnnotationProcessor() {
return new ScheduledAnnotationBeanPostProcessor();
}
}

The second category : Select configuration class according to conditions

EnableAsync Annotate the core code :

@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 Ordered.LOWEST_PRECEDENCE;
}

AsyncConfigurationSelector Select the configuration class to be imported through the condition , AsyncConfigurationSelector The root interface of is ImportSelector, This interface needs to be rewritten selectImports Method , In this method, the prior conditions are judged .

In the source code below , if adviceMode by PORXY, Then return to ProxyAsyncConfiguration This configuration class . if activeMode by ASPECTJ, Then return to AspectJAsyncConfiguration Configuration class . Source code is as follows :

public class AsyncConfigurationSelector extends AdviceModeImportSelector<EnableAsync> {
private static final String ASYNC_EXECUTION_ASPECT_CONFIGURATION_CLASS_NAME =
"org.springframework.scheduling.aspectj.AspectJAsyncConfiguration";
/**
* {@inheritDoc}
* @return {@link ProxyAsyncConfiguration} or {@code AspectJAsyncConfiguration} for
* {@code PROXY} and {@code ASPECTJ} values of {@link EnableAsync#mode()}, respectively
*/
@Override
public String[] selectImports(AdviceMode adviceMode) {
switch (adviceMode) {
case PROXY:
return new String[] { ProxyAsyncConfiguration.class.getName() };
case ASPECTJ:
return new String[] { ASYNC_EXECUTION_ASPECT_CONFIGURATION_CLASS_NAME };
default:
return null;
}
}
}

The third category : Dynamic registration Bean

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

AspectJAutoProxyRegistrar In advance ImportBeanDefinitionRegistrar Interface ,ImportBeanDefinitionRegistrar The role of is to automatically add... At run time Bean To the existing configuration class , By overriding the method :

@Override
public void registerBeanDefinitions(
AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry)

among ,AnnotationMetadata Parameter is used to get the annotation on the current configuration class ; BeanDefinittionRegistry Parameter is used to register Bean. Source code is as follows :

class AspectJAutoProxyRegistrar implements ImportBeanDefinitionRegistrar {
/**
* Register, escalate, and configure the AspectJ auto proxy creator based on the value
* of the @{@link EnableAspectJAutoProxy#proxyTargetClass()} attribute on the importing
* {@code @Configuration} class.
*/
@Override
public void registerBeanDefinitions(
AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
AopConfigUtils.registerAspectJAnnotationAutoProxyCreatorIfNecessary(registry);
AnnotationAttributes enableAJAutoProxy =
AnnotationConfigUtils.attributesFor(importingClassMetadata, EnableAspectJAutoProxy.class);
if (enableAJAutoProxy.getBoolean("proxyTargetClass")) {
AopConfigUtils.forceAutoProxyCreatorToUseClassProxying(registry);
}
}
}

This article is written by [ Familiar with memory ] To write , All rights reserved .

Reprint please indicate the source :http://blog.csdn.net/qq_26525215 This article comes from College trip _ The blog of memory

Participation of this paper Tencent cloud media sharing plan , You are welcome to join us , share .

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