Spring Boot 2.x AutoConfiguratio

作者: ZozoSpider | 来源:发表于2018-10-12 23:29 被阅读0次

Spring 模式注解装配

Spring Annotation Programming Model

A stereotype annotation is an annotation that is used to declare the role that a component plays within the application. For example, the @Repository annotation in the Spring Framework is a marker for any class that fulfills the role or stereotype of a repository (also known as Data Access Object or DAO).

@Component is a generic stereotype for any Spring-managed component. Any component annotated with @Component is a candidate for component scanning. Similarly, any component annotated with an annotation that is itself meta-annotated with @Component is also a candidate for component scanning. For example, @Service is meta-annotated with @Component.

模式注解是一种用于声明在应用中扮演“组件”角色的注解。如Spring Framework中的@Repository标注在任何类上，用于扮演仓储角色的模式注解。

@Component作为一种由Spring容器托管的通用模式组件，任何被@Component标准的组件均为组件扫描的候选对象。类似地，凡是被@Component元标注（meta-annotated）的注解，如@Service，当任何组件标注它时，也被视作组件扫描的候选对象。

Spring 模式注解装配 -> 举例

Spring Framework 注解	场景说明	起始版本
`@Component`	通用组件模式注解	2.5
`@Repository`	数据仓储模式注解	2.0
`@Service`	服务模式注解	2.5
`@Controller`	Web控制器模式注解	2.5
`@Configuration`	配置类模式注解	3.0

Spring 模式注解装配 -> 装配方式: @ComponentScan & <context:component-scan>

Spring Framework 5.1.0 Classpath Scanning and Managed Components

要自动检测这些类并注册相应的bean，您需要将 @ComponentScan 添加到 @Configuration 类

@Configuration
@ComponentScan(basePackages = "org.example")
public class AppConfig  {
    ...
}

等价xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context.xsd">

    <!-- 激活注解驱动特性 -->
    <context:annotation-config>

    <!-- 找寻被 @Component 或者其派生 Annotation 标记的类（Class），将它们注册为 Spring Bean -->
    <context:component-scan base-package="org.example"/>

</beans>

以下示例显示忽略所有@Repository注释并使用“存根”存储库的配置

@Configuration
@ComponentScan(basePackages = "org.example",
        includeFilters = @Filter(type = FilterType.REGEX, pattern = ".*Stub.*Repository"),
        excludeFilters = @Filter(Repository.class))
public class AppConfig {
    ...
}

等价xml

<beans>
    <context:component-scan base-package="org.example">
        <context:include-filter type="regex"
                expression=".*Stub.*Repository"/>
        <context:exclude-filter type="annotation"
                expression="org.springframework.stereotype.Repository"/>
    </context:component-scan>
</beans>

Spring 模式注解装配 -> 自定义

定义注解 @FirstLevelRepository ，从 @Repository 派生，其中， @Repository 从 @Component 派生。
@FirstLevelRepository > @Repository > @Component

import org.springframework.stereotype.Repository;

import java.lang.annotation.*;

/**
 * 一级 {@link Repository @Repository}
 *
 * @author zoz
 * @since 1.0
 */
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Repository
public @interface FirstLevelRepository {

    String value() default "";

}

定义注解 @SecondLevelRepository ，从 @FirstLevelRepository 派生。
@SecondLevelRepository > @FirstLevelRepository > @Repository > @Component

import org.springframework.stereotype.Repository;

import java.lang.annotation.*;

/**
 * 二级 {@link Repository}
 *
 * @author zoz
 * @since 1.0
 */
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@FirstLevelRepository
public @interface SecondLevelRepository {

    String value() default "";

}

定义类引用注解 @FirstLevelRepository

package com.imooc.diveinspringboot.configuration.repository;

import com.imooc.diveinspringboot.configuration.annotation.FirstLevelRepository;

@FirstLevelRepository(value = "myFirstLevelRepository")
public class MyFirstLevelRepository {

}

定义类引用注解 @SecondLevelRepository

package com.imooc.diveinspringboot.configuration.repository;

import com.imooc.diveinspringboot.configuration.annotation.SecondLevelRepository;

@SecondLevelRepository(value = "mySecondLevelRepository")
public class MySecondLevelRepository {
    
}

启动类，通过 @ComponentScan 扫描所有引用了注解 @Component 或其派生的类，并获取类的实体。

import com.imooc.diveinspringboot.configuration.repository.MyFirstLevelRepository;
import com.imooc.diveinspringboot.configuration.repository.MySecondLevelRepository;
import org.springframework.boot.WebApplicationType;
import org.springframework.boot.builder.SpringApplicationBuilder;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.ComponentScan;

@ComponentScan(basePackages = "com.imooc.diveinspringboot.configuration.repository")
public class RepositoryBootstrap {

    public static void main(String[] args) {

        ConfigurableApplicationContext context = new SpringApplicationBuilder(RepositoryBootstrap.class)
                .web(WebApplicationType.NONE)
                .run(args);

        MyFirstLevelRepository myFirstLevelRepository = context.getBean("myFirstLevelRepository", MyFirstLevelRepository.class);
        MySecondLevelRepository mySecondLevelRepository = context.getBean("mySecondLevelRepository", MySecondLevelRepository.class);

        System.out.println("myFirstLevelRepository Bean: " + myFirstLevelRepository);
        System.out.println("mySecondLevelRepository Bean: " + mySecondLevelRepository);

        // 关闭上下文
        context.close();

    }

}

Spring 模式 @Enable 模块装配

Spring Framework 3.1 开始支持 @Enable 模块装配，即将具有相同领域的功能组件集合，组合成一个独立的单元。

Spring 模式 @Enable 模块装配 -> 举例

框架实现	`@Enable` 注解模块	激活模块
Spring Framework	`@EnableWebMvc`	Web MVC 模块
	`@EnableTransactionManagement`	事务管理模块
	`@EnableCaching`	Caching 模块
	`@EnableMBeanExport`	JMX 模块
	`@EnableAsync`	异步处理模块
	`@EnableWebFlux`	Web Flux 模块
	`@EnableAspectJAutoProxy`	AspectJ 代理模块

Spring Boot	`@EnableAutoConfiguration`	自动装配模块
	`@EnableManagementContext`	Actuator 模块
	`@EnableConfigurationProperties`	配置属性绑定模块
	`@EnableOAuth2Sso`	OAuth2 单点登录模块
Spring Cloud
	`@EnableEurekaServer`	Eureka 服务器模块
	`@EnableConfigServer`	配置服务器模块
	`@EnableFeignClients`	Feign 客户端模块
	`@EnableZuulProxy`	服务网关 Zuul 模块
	`@EnableCircuitBreaker`	服务熔断模块

Spring 模式 @Enable 模块装配 -> 实现方式: 注解驱动

Spring Framework @EnableWebMvc 导入 DelegatingWebMvcConfiguration

package org.springframework.web.servlet.config.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;

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
@Documented
@Import(DelegatingWebMvcConfiguration.class)
public @interface EnableWebMvc {

}

DelegatingWebMvcConfiguration 添加 @Configuration 注解

@Configuration
public class DelegatingWebMvcConfiguration extends WebMvcConfigurationSupport {

    private final WebMvcConfigurerComposite configurers = new WebMvcConfigurerComposite();

    @Autowired(required = false)
    public void setConfigurers(List<WebMvcConfigurer> configurers) {
        if (!CollectionUtils.isEmpty(configurers)) {
            this.configurers.addWebMvcConfigurers(configurers);
        }
    }

    @Override
    protected void configurePathMatch(PathMatchConfigurer configurer) {
        this.configurers.configurePathMatch(configurer);
    }

    ...

}

自定义 @EnableHelloConfiguration 导入 HelloConfiguration

import com.imooc.diveinspringboot.configuration.configuration.HelloConfiguration;
import org.springframework.context.annotation.Import;

import java.lang.annotation.*;

/**
 * 激活 Hello 模块
 *
 * @author zozo
 * @since 1.0
 */
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
@Documented
@Import(HelloConfiguration.class)
public @interface EnableHelloConfiguration {

}

HelloConfiguration 添加 @Configuration 注解

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

/**
 * Hello 配置
 *
 * @author zozo
 * @since 1.0
 */
@Configuration
public class HelloConfiguration {

    @Bean
    public String hello() { // 方法名即 Bean 名称
        return "Hello Bean";
    }

}

引用 & 运行结果

import com.imooc.diveinspringboot.configuration.annotation.EnableHelloConfiguration;
import org.springframework.boot.WebApplicationType;
import org.springframework.boot.builder.SpringApplicationBuilder;
import org.springframework.context.ConfigurableApplicationContext;

@EnableHelloConfiguration
public class EnableHelloConfigurationBootstrap {

    public static void main(String[] args) {

        ConfigurableApplicationContext context = new SpringApplicationBuilder(EnableHelloConfigurationBootstrap.class)
                .web(WebApplicationType.NONE)
                .run(args);

        // 查找 Bean
        String hello = context.getBean("hello", String.class);

        System.out.println("hello Bean: " + hello);

        // 关闭上下文
        context.close();

    }

}

hello Bean: Hello Bean

Spring 模式 @Enable 模块装配 -> 实现方式: 接口编程

Spring Framework @EnableCaching 导入 CachingConfigurationSelector

package org.springframework.cache.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.AdviceMode;
import org.springframework.context.annotation.Import;
import org.springframework.core.Ordered;

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Import(CachingConfigurationSelector.class)
public @interface EnableCaching {

    boolean proxyTargetClass() default false;

    AdviceMode mode() default AdviceMode.PROXY;

    int order() default Ordered.LOWEST_PRECEDENCE;

}

CachingConfigurationSelector 继承 AdviceModeImportSelector 实现 ImportSelector 接口

public class CachingConfigurationSelector extends AdviceModeImportSelector<EnableCaching> {

    private static final String PROXY_JCACHE_CONFIGURATION_CLASS =
            "org.springframework.cache.jcache.config.ProxyJCacheConfiguration";

    private static final String CACHE_ASPECT_CONFIGURATION_CLASS_NAME =
            "org.springframework.cache.aspectj.AspectJCachingConfiguration";

    ...

    @Override
    public String[] selectImports(AdviceMode adviceMode) {
        switch (adviceMode) {
            case PROXY:
                return getProxyImports();
            case ASPECTJ:
                return getAspectJImports();
            default:
                return null;
        }
    }

    private String[] getProxyImports() {
        List<String> result = new ArrayList<>(3);
        result.add(AutoProxyRegistrar.class.getName());
        result.add(ProxyCachingConfiguration.class.getName());
        if (jsr107Present && jcacheImplPresent) {
            result.add(PROXY_JCACHE_CONFIGURATION_CLASS);
        }
        return StringUtils.toStringArray(result);
    }

    ...

}

自定义 @EnableHelloImportSelector 导入 HelloImportSelector

import com.imooc.diveinspringboot.configuration.configuration.HelloImportSelector;
import org.springframework.context.annotation.Import;

import java.lang.annotation.*;

/**
 * 激活 Hello 模块
 *
 * @author zozo
 * @since 1.0
 */
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
@Documented
@Import(HelloImportSelector.class)
public @interface EnableHelloImportSelector {

}

HelloImportSelector 实现 ImportSelector 接口

import org.springframework.context.annotation.ImportSelector;
import org.springframework.core.type.AnnotationMetadata;

/**
 * Hello {@link ImportSelector} 实现
 *
 * @author zozo
 * @since 1.0
 */
public class HelloImportSelector implements ImportSelector {

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

}

引用 & 运行结果

import com.imooc.diveinspringboot.configuration.annotation.EnableHelloImportSelector;
import org.springframework.boot.WebApplicationType;
import org.springframework.boot.builder.SpringApplicationBuilder;
import org.springframework.context.ConfigurableApplicationContext;

@EnableHelloImportSelector
public class EnableHelloImportSelectorBootstrap {

    public static void main(String[] args) {

        ConfigurableApplicationContext context = new SpringApplicationBuilder(EnableHelloImportSelectorBootstrap.class)
                .web(WebApplicationType.NONE)
                .run(args);

        // 查找 Bean
        String hello = context.getBean("hello", String.class);

        System.out.println("hello Bean: " + hello);

        // 关闭上下文
        context.close();
    }

}

hello Bean: Hello Bean

Spring Boot 2.x AutoConfiguratio

Spring 模式注解装配

Spring 模式注解装配 -> 举例

Spring 模式注解装配 -> 装配方式: @ComponentScan & <context:component-scan>

Spring 模式注解装配 -> 自定义

Spring 模式 @Enable 模块装配

Spring 模式 @Enable 模块装配 -> 举例

Spring 模式 @Enable 模块装配 -> 实现方式: 注解驱动

Spring 模式 @Enable 模块装配 -> 实现方式: 接口编程

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