[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 annotation Activate Aspect Automatic agent


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 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 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 Annotations are used to open Web MVC Configuration support for .

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


@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 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 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 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;
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,
* 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
public class SchedulingConfiguration {
public ScheduledAnnotationBeanPostProcessor scheduledAnnotationProcessor() {
return new ScheduledAnnotationBeanPostProcessor();

The second category : Select configuration class according to conditions

EnableAsync Annotate the core code :

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> {
* {@inheritDoc}
* @return {@link ProxyAsyncConfiguration} or {@code AspectJAsyncConfiguration} for
* {@code PROXY} and {@code ASPECTJ} values of {@link EnableAsync#mode()}, respectively
public String[] selectImports(AdviceMode adviceMode) {
switch (adviceMode) {
case PROXY:
return new String[] { ProxyAsyncConfiguration.class.getName() };
return null;

The third category : Dynamic registration Bean

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 :

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.
public void registerBeanDefinitions(
AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
AnnotationAttributes enableAJAutoProxy =
AnnotationConfigUtils.attributesFor(importingClassMetadata, EnableAspectJAutoProxy.class);
if (enableAJAutoProxy.getBoolean("proxyTargetClass")) {

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

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