springboot如何实现自动装配源码解读

Spring Boot 自动装配

最重要的注解@SpringBootApplication

@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 {

	@AliasFor(annotation = EnableAutoConfiguration.class)
	Class<?>[] exclude() default {};

	@AliasFor(annotation = EnableAutoConfiguration.class)
	String[] excludeName() default {};

	@AliasFor(annotation = ComponentScan.class, attribute = "basePackages")
	String[] scanBasePackages() default {};

	@AliasFor(annotation = ComponentScan.class, attribute = "basePackageClasses")
	Class<?>[] scanBasePackageClasses() default {};

	@AliasFor(annotation = Configuration.class)
	boolean proxyBeanMethods() default true;

}

EnableAutoConfiguration

是实现自动装配的核心注解

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

getAutoConfigurationMetadata()

@Override
public void process(AnnotationMetadata annotationMetadata, DeferredImportSelector deferredImportSelector) {
	Assert.state(deferredImportSelector instanceof AutoConfigurationImportSelector,
			() -> String.format("Only %s implementations are supported, got %s",
					AutoConfigurationImportSelector.class.getSimpleName(),
					deferredImportSelector.getClass().getName()));
	AutoConfigurationEntry autoConfigurationEntry = ((AutoConfigurationImportSelector) deferredImportSelector)
			.getAutoConfigurationEntry(
					// 加载配置元数据
					getAutoConfigurationMetadata(), annotationMetadata);
	this.autoConfigurationEntries.add(autoConfigurationEntry);
	for (String importClassName : autoConfigurationEntry.getConfigurations()) {
		this.entries.putIfAbsent(importClassName, annotationMetadata);
	}
}


private AutoConfigurationMetadata getAutoConfigurationMetadata() {
	if (this.autoConfigurationMetadata == null) {
		// 加载配置信息
		this.autoConfigurationMetadata = AutoConfigurationMetadataLoader.loadMetadata(this.beanClassLoader);
	}
	return this.autoConfigurationMetadata;
}
static AutoConfigurationMetadata loadMetadata(ClassLoader classLoader, String path) {
	try {

	  // 获取资源路径
		Enumeration<URL> urls = (classLoader != null) ? classLoader.getResources(path)
				: ClassLoader.getSystemResources(path);
		Properties properties = new Properties();
		while (urls.hasMoreElements()) {
			properties.putAll(PropertiesLoaderUtils.loadProperties(new UrlResource(urls.nextElement())));
		}
		return loadMetadata(properties);
	}
	catch (IOException ex) {
		throw new IllegalArgumentException("Unable to load @ConditionalOnClass location [" + path + "]", ex);
	}
}

protected static final String PATH = "META-INF/spring-autoconfigure-metadata.properties";

注意： 这个文件在target编译后的文件夹中
自动装配

spring-boot-project/spring-boot-autoconfigure/src/main/resources/META-INF/spring.factories

该文件内存有:

Auto Configure

org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
org.springframework.boot.autoconfigure.admin.SpringApplicationAdminJmxAutoConfiguration,\
org.springframework.boot.autoconfigure.aop.AopAutoConfiguration,\
org.springframework.boot.autoconfigure.amqp.RabbitAutoConfiguration,\
org.springframework.boot.autoconfigure.batch.BatchAutoConfiguration,\
org.springframework.boot.autoconfigure.cache.CacheAutoConfiguration,\

EnableConfigurationProperties

@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;

	/**
	 * Client name to be set on connections with CLIENT SETNAME.
	 */
	private String clientName;	

}

希望通过本篇对于springboot自动装配的解读，让大家对springboot底层有了一个大致了解，只分析了主要方法，希望对大家有帮助

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