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

来源：https://blog.csdn.net/weixin_44302240/article/details/110630566