layout:
title: 5-Enable注解工作原理
date: 2017-02-05
updated: 2017-02-05
tags:
- SpringBoot
- SpringBoot与微服务
- SpringBoot实战与原理
- Spring
- 原理
categories: SpringBoot实战与原理分析
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5-Enable注解工作原理
5.1 Enable注解用法
- 把配置文件里的属性注入到bean中
package com.clsaa.edu.springboot;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.ComponentScan;
/**
* EnableConfigurationProperties是用来启用一个特性的
* 这个特性可以把配置文件的属性注入到bean里面去
*/
@EnableConfigurationProperties
@ComponentScan
public class App {
public static void main(String[] args) {
ConfigurableApplicationContext context = SpringApplication.run(App.class,args);
System.out.println(context.getBeansOfType(TomcatProperties.class));
context.close();
}
}
package com.clsaa.edu.springboot;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.stereotype.Component;
/**
* Created by Egg on 2017/2/23.
*/
@Component
@ConfigurationProperties(prefix = "tomcat")
public class TomcatProperties {
private String host;
private Integer port;
public String getHost() {
return host;
}
public void setHost(String host) {
this.host = host;
}
public Integer getPort() {
return port;
}
public void setPort(Integer port) {
this.port = port;
}
@Override
public String toString() {
return "TomcatProperties{" +
"host='" + host + '\'' +
", port=" + port +
'}';
}
}
- 使用spring启用一个异步
- @EnableAsync启用异步
- @Async标记异步
package com.clsaa.edu.springboot;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.scheduling.annotation.EnableAsync;
@EnableConfigurationProperties
@EnableAsync
@ComponentScan
public class App {
public static void main(String[] args) {
ConfigurableApplicationContext context = SpringApplication.run(App.class,args);
System.out.println("====start====");
context.getBean(Jeep.class).run();
System.out.println("====end====");
context.close();
}
}
package com.clsaa.edu.springboot;
import ch.qos.logback.core.util.TimeUtil;
import org.springframework.scheduling.annotation.Async;
import org.springframework.stereotype.Component;
import java.util.concurrent.TimeUnit;
/**
* Created by Egg on 2017/2/23.
*/
@Component
public class Jeep implements Runnable {
@Override
@Async
public void run() {
try {
for (int i = 0 ; i < 10 ; i++) {
System.out.println("================="+i);
TimeUnit.SECONDS.sleep(1);
}
}catch (InterruptedException e) {
e.printStackTrace();
}
}
}
5.2 Enable注解源码分析
/**
* Enable support for {@link ConfigurationProperties} annotated beans.
* {@link ConfigurationProperties} beans can be registered in the standard way (for
* example using {@link Bean @Bean} methods) or, for convenience, can be specified
* directly on this annotation.
*
* @author Dave Syer
*/
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Import(EnableConfigurationPropertiesImportSelector.class)
public @interface EnableConfigurationProperties {
/**
* Convenient way to quickly register {@link ConfigurationProperties} annotated beans
* with Spring. Standard Spring Beans will also be scanned regardless of this value.
* @return {@link ConfigurationProperties} annotated beans to register
*/
Class<?>[] value() default {};
}
- Enable注解的核心在于@Import
package org.springframework.context.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;
/**
* Indicates one or more {@link Configuration @Configuration} classes to import.
*
* <p>Provides functionality equivalent to the {@code <import/>} element in Spring XML.
* Allows for importing {@code @Configuration} classes, {@link ImportSelector} and
* {@link ImportBeanDefinitionRegistrar} implementations, as well as regular component
* classes (as of 4.2; analogous to {@link AnnotationConfigApplicationContext#register}).
*
* <p>{@code @Bean} definitions declared in imported {@code @Configuration} classes should be
* accessed by using {@link org.springframework.beans.factory.annotation.Autowired @Autowired}
* injection. Either the bean itself can be autowired, or the configuration class instance
* declaring the bean can be autowired. The latter approach allows for explicit, IDE-friendly
* navigation between {@code @Configuration} class methods.
*
* <p>May be declared at the class level or as a meta-annotation.
*
* <p>If XML or other non-{@code @Configuration} bean definition resources need to be
* imported, use the {@link ImportResource @ImportResource} annotation instead.
*
* @author Chris Beams
* @author Juergen Hoeller
* @since 3.0
* @see Configuration
* @see ImportSelector
* @see ImportResource
*/
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Import {
/**
* {@link Configuration}, {@link ImportSelector}, {@link ImportBeanDefinitionRegistrar}
* or regular component classes to import.
*/
Class<?>[] value();
}
- @Import的用法
- 用来导入一个或者多个类(会被spring容器托管)
- 或者导入配置类(配置类里的bean都会被spring容器托管)
package com.clsaa.edu.springboot;
import org.springframework.boot.SpringApplication;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Import;
/**
* Created by Egg on 2017/2/23.
*/
@ComponentScan
@Import({User.class,Role.class,MyConfiguration.class})
public class Application {
public static void main(String[] args) {
ConfigurableApplicationContext context = SpringApplication.run(Application.class,args);
System.out.println(context.getBean(User.class));
System.out.println(context.getBean(Role.class));
System.out.println(context.getBean(Runnable.class));
context.close();
}
}
package com.clsaa.edu.springboot;
import org.springframework.context.annotation.Bean;
/**
* Created by Egg on 2017/2/23.
*/
public class MyConfiguration {
@Bean
public Runnable createRunnable(){
return ()->{};
}
}
package com.clsaa.edu.springboot;
/**
* Created by Egg on 2017/2/23.
*/
public class User {
}
- @Import的核心在于ImportSelector
- 能根据业务逻辑(配置的注解)动态的返回一个字符串数组
package com.clsaa.edu.springboot;
import org.springframework.boot.SpringApplication;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Import;
@ComponentScan
//@Import({User.class,Role.class,MyConfiguration.class})
@Import(MyImportSelector.class)
public class Application {
public static void main(String[] args) {
ConfigurableApplicationContext context = SpringApplication.run(Application.class,args);
System.out.println(context.getBean(User.class));
System.out.println(context.getBean(Role.class));
context.close();
}
}
package com.clsaa.edu.springboot;
import org.springframework.context.annotation.ImportSelector;
import org.springframework.core.type.AnnotationMetadata;
public class MyImportSelector implements ImportSelector {
@Override
public String[] selectImports(AnnotationMetadata importingClassMetadata) {
return new String[]{"com.clsaa.edu.springboot.User","com.clsaa.edu.springboot.MyConfiguration","com.clsaa.edu.springboot.Role"};
}
}
- 另外还要注意ImportBeanDefinitionRegistrar这个接口
- 与之前的类似我们可以用这个接口提供的函数中的registry参数往容器中注入bean
public interface ImportBeanDefinitionRegistrar {
/**
* Register bean definitions as necessary based on the given annotation metadata of
* the importing {@code @Configuration} class.
* <p>Note that {@link BeanDefinitionRegistryPostProcessor} types may <em>not</em> be
* registered here, due to lifecycle constraints related to {@code @Configuration}
* class processing.
* @param importingClassMetadata annotation metadata of the importing class
* @param registry current bean definition registry
*/
public void registerBeanDefinitions(
AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry);
}
