springboot自动配置原理解析

<dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-redis</artifactId>
            <version>2.1.7.RELEASE</version>
        </dependency>
</dependencies>

spring.redis.port=6379
spring.redis.host=localhost
spring.redis.database=0

@RequestMapping("/redistest")
    public String test(){
        redisTemplate.opsForSet().add("aaaaa","123456");
        return "OK";
    }

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@SpringBootConfiguration
@EnableAutoConfiguration
@ComponentScan(excludeFilters = { @Filter(type = FilterType.CUSTOM, classes = TypeExcludeFilter.class),
		@Filter(type = FilterType.CUSTOM, classes = AutoConfigurationExcludeFilter.class) })
public @interface SpringBootApplication 

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@AutoConfigurationPackage
@Import(AutoConfigurationImportSelector.class)
public @interface EnableAutoConfiguration

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@Import(AutoConfigurationPackages.Registrar.class)
public @interface AutoConfigurationPackage {

}

static class Registrar implements ImportBeanDefinitionRegistrar, DeterminableImports {

        //metadata是注解的元信息 registry是bean定义的注册器
		@Override
		public void registerBeanDefinitions(AnnotationMetadata metadata, BeanDefinitionRegistry registry) {
            //把注解所在的包下所有的组件都进行注册
			register(registry, new PackageImport(metadata).getPackageName());
		}

		@Override
		public Set<Object> determineImports(AnnotationMetadata metadata) {
			return Collections.singleton(new PackageImport(metadata));
		}

	}




public static void register(BeanDefinitionRegistry registry, String... packageNames) {
		//首先判断这个bean有没有被注册
		if (registry.containsBeanDefinition(BEAN)) {
			//获取bean定义
			BeanDefinition beanDefinition = registry.getBeanDefinition(BEAN);
			//通过bean定义获取构造函数值
			ConstructorArgumentValues constructorArguments = beanDefinition.getConstructorArgumentValues();
			//给构造函数添加参数值
			constructorArguments.addIndexedArgumentValue(0, addBasePackages(constructorArguments, packageNames));
		}
		else {
			//一个新的bean定义
			GenericBeanDefinition beanDefinition = new GenericBeanDefinition();
			//设置beanClass为beanPackages类型
			beanDefinition.setBeanClass(BasePackages.class);
			beanDefinition.getConstructorArgumentValues().addIndexedArgumentValue(0, packageNames);
			beanDefinition.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
			//bean注册
			registry.registerBeanDefinition(BEAN, beanDefinition);
		}
	}

@Override
	public String[] selectImports(AnnotationMetadata annotationMetadata) {
		if (!isEnabled(annotationMetadata)) {
			return NO_IMPORTS;
		}
		//加载元数据
		AutoConfigurationMetadata autoConfigurationMetadata = AutoConfigurationMetadataLoader
				.loadMetadata(this.beanClassLoader);
		//获得自动装配的实体
		AutoConfigurationEntry autoConfigurationEntry = getAutoConfigurationEntry(autoConfigurationMetadata,
				annotationMetadata);
		return StringUtils.toStringArray(autoConfigurationEntry.getConfigurations());
	}

protected AutoConfigurationEntry getAutoConfigurationEntry(AutoConfigurationMetadata autoConfigurationMetadata,
			AnnotationMetadata annotationMetadata) {
		if (!isEnabled(annotationMetadata)) {
			return EMPTY_ENTRY;
		}
		//获得属性
		AnnotationAttributes attributes = getAttributes(annotationMetadata);
		//获得候选的配置类，核心方法
		List<String> configurations = getCandidateConfigurations(annotationMetadata, attributes);
		//去除重复
		configurations = removeDuplicates(configurations);
		//获得排除的配置
		Set<String> exclusions = getExclusions(annotationMetadata, attributes);
		//检查排除的配置
		checkExcludedClasses(configurations, exclusions);
		//排除
		configurations.removeAll(exclusions);
		configurations = filter(configurations, autoConfigurationMetadata);
		fireAutoConfigurationImportEvents(configurations, exclusions);
		return new AutoConfigurationEntry(configurations, exclusions);
	}

protected List<String> getCandidateConfigurations(AnnotationMetadata metadata, AnnotationAttributes attributes) {
		//从工厂中获取自动配置类
		List<String> configurations = SpringFactoriesLoader.loadFactoryNames(getSpringFactoriesLoaderFactoryClass(),
				getBeanClassLoader());
		//这句断言很重要，告诉了我们工厂是去哪里找自动配置类的,这里显然META-INF/spring.factories是一个路径
		Assert.notEmpty(configurations, "No auto configuration classes found in META-INF/spring.factories. If you "
				+ "are using a custom packaging, make sure that file is correct.");
		return configurations;
	}

org.springframework.boot.autoconfigure.data.redis.RedisAutoConfiguration,\
org.springframework.boot.autoconfigure.data.redis.RedisReactiveAutoConfiguration,\
org.springframework.boot.autoconfigure.data.redis.RedisRepositoriesAutoConfiguration,\

@Configuration
//条件注解，某个class位于类路径上，才会实例化一个Bean，这个类是redis操作的类
@ConditionalOnClass(RedisOperations.class)
//使得@ConfigurationProperties 注解的类生效，这个类是配置redis属性的类
@EnableConfigurationProperties(RedisProperties.class)
//导入一些配置
@Import({ LettuceConnectionConfiguration.class, JedisConnectionConfiguration.class })
public class RedisAutoConfiguration {

	@Bean
	//仅仅在当前上下文中不存在某个对象时，才会实例化一个Bean，这个就是spring默认的redisTemplate
	@ConditionalOnMissingBean(name = "redisTemplate")
	public RedisTemplate<Object, Object> redisTemplate(RedisConnectionFactory redisConnectionFactory)
			throws UnknownHostException {
		RedisTemplate<Object, Object> template = new RedisTemplate<>();
		template.setConnectionFactory(redisConnectionFactory);
		return template;
	}

	@Bean
	@ConditionalOnMissingBean
	public StringRedisTemplate stringRedisTemplate(RedisConnectionFactory redisConnectionFactory)
			throws UnknownHostException {
		StringRedisTemplate template = new StringRedisTemplate();
		template.setConnectionFactory(redisConnectionFactory);
		return template;
	}

}

//前缀spring.redis
@ConfigurationProperties(prefix = "spring.redis")
public class RedisProperties {

	/**
	 * Database index used by the connection factory.
	 */
	private int database = 0;

	/**
	 * Connection URL. Overrides host, port, and password. User is ignored. Example:
	 * redis://user:password@example.com:6379
	 */
	private String url;

	/**
	 * Redis server host.
	 */
	private String host = "localhost";

	/**
	 * Login password of the redis server.
	 */
	private String password;

	/**
	 * Redis server port.
	 */
	private int port = 6379;

	/**
	 * Whether to enable SSL support.
	 */
	private boolean ssl;

	/**
	 * Connection timeout.
	 */
	private Duration timeout;

	private Sentinel sentinel;

	private Cluster cluster;

	private final Jedis jedis = new Jedis();

	private final Lettuce lettuce = new Lettuce();
}

@Configuration
public class RedisConfig {
    //这里的上下文已经有了自定义的redisTemplate，所以默认的redisTemplate不会生效
    @Bean
    public RedisTemplate<Object,Object> redisTemplate(RedisConnectionFactory redisConnectionFactory)  {
        RedisTemplate<Object,Object> redisTemplate=new RedisTemplate<>();
        //设置自定义序列化器
        redisTemplate.setDefaultSerializer(new Jackson2JsonRedisSerializer<Object>(Object.class));
        redisTemplate.setConnectionFactory(redisConnectionFactory);
        return redisTemplate;
    }
}

public String test(){
        redisTemplate.opsForSet().add("ffffff","55555555");
        return "OK";
    }