springboot自动装配流程源码讲解（以REDIS为例）
- springboot找到了@EnableAutoConfiguration注解
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@SpringBootConfiguration
@EnableAutoConfiguration //开启自动配置注解
@ComponentScan(excludeFilters = { @Filter(type = FilterType.CUSTOM, classes = TypeExcludeFilter.class),
@Filter(type = FilterType.CUSTOM, classes = AutoConfigurationExcludeFilter.class) })
public @interface SpringBootApplication {
- 使用@Import注解导入了AutoConfigurationImportSelector类
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@AutoConfigurationPackage
@Import(AutoConfigurationImportSelector.class) //导入AutoConfigurationImportSelector.class
public @interface EnableAutoConfiguration {
- AutoConfigurationImportSelector调用selectImports()方法导入jar包下的meta-info/spring.factories找到所有EnableAutoConfiguration为key的集合，根据Maven依赖导入的jar来筛选配置类
@Override
public String[] selectImports(AnnotationMetadata annotationMetadata) {
if (!isEnabled(annotationMetadata)) {
return NO_IMPORTS;
}
AutoConfigurationMetadata autoConfigurationMetadata = AutoConfigurationMetadataLoader
.loadMetadata(this.beanClassLoader);
AutoConfigurationEntry autoConfigurationEntry = getAutoConfigurationEntry(autoConfigurationMetadata,
annotationMetadata);
return StringUtils.toStringArray(autoConfigurationEntry.getConfigurations());
}
protected AutoConfigurationEntry getAutoConfigurationEntry(AutoConfigurationMetadata autoConfigurationMetadata,
AnnotationMetadata annotationMetadata) {
if (!isEnabled(annotationMetadata)) {
return EMPTY_ENTRY;
}
AnnotationAttributes attributes = getAttributes(annotationMetadata);
List configurations = getCandidateConfigurations(annotationMetadata, attributes);
///去除重复的配置类，若我们自己写的starter 可能存主重复的
configurations = removeDuplicates(configurations);
Set exclusions = getExclusions(annotationMetadata, attributes);
checkExcludedClasses(configurations, exclusions);
configurations.removeAll(exclusions);
//根据maven 导入的启动器过滤出 需要导入的配置类
configurations = filter(configurations, autoConfigurationMetadata);
fireAutoConfigurationImportEvents(configurations, exclusions);
return new AutoConfigurationEntry(configurations, exclusions);
}
//导入 META-INF/spring.factories文件，查找对应的EnableAutoConfiguration配置
protected List getCandidateConfigurations(AnnotationMetadata metadata, AnnotationAttributes attributes) {
List configurations = SpringFactoriesLoader.loadFactoryNames(getSpringFactoriesLoaderFactoryClass(),
getBeanClassLoader());
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;
}
//进入SpringFactoriesLoader.loadFactoryNames 方法可以看到loadSpringFactories方法
private static Map> loadSpringFactories(@Nullable ClassLoader classLoader) {
MultiValueMap result = cache.get(classLoader);
if (result != null) {
return result;
}
try {
Enumeration urls = (classLoader != null ?
classLoader.getResources(FACTORIES_RESOURCE_LOCATION) :
ClassLoader.getSystemResources(FACTORIES_RESOURCE_LOCATION));
result = new LinkedMultiValueMap<>();
while (urls.hasMoreElements()) {
URL url = urls.nextElement();
UrlResource resource = new UrlResource(url);
Properties properties = PropertiesLoaderUtils.loadProperties(resource);
for (Map.Entry entry : properties.entrySet()) {
String factoryTypeName = ((String) entry.getKey()).trim();
for (String factoryImplementationName : StringUtils.commaDelimitedListToStringArray((String) entry.getValue())) {
result.add(factoryTypeName, factoryImplementationName.trim());
}
}
}
cache.put(classLoader, result);
return result;
}
catch (IOException ex) {
throw new IllegalArgumentException("Unable to load factories from location [" +
FACTORIES_RESOURCE_LOCATION + "]", ex);
}
}
- 因为导入了spring-boot-starter-data-redis的Maven依赖，因此RedisAutoConfiguration配置类会起作用（利用@ ConditionalOnClass注解）
@Configuration(proxyBeanMethods = false)
//当引入到RedisOperation类，配置才会生效
@ConditionalOnClass(RedisOperations.class)
@EnableConfigurationProperties(RedisProperties.class)
@Import({ LettuceConnectionConfiguration.class, JedisConnectionConfiguration.class })
public class RedisAutoConfiguration {
@Bean
@ConditionalOnMissingBean(name = "redisTemplate")
public RedisTemplate redisTemplate(RedisConnectionFactory redisConnectionFactory)
throws UnknownHostException {
RedisTemplate 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;
}
}
- @EnableConfigurationProperties(RedisProperties.class)开启读取RedisProperties映射的配置，进入该注解查看源码可以看到引入了EnableConfigurationPropertiesRegistrar.class类
EnableConfigurationPropertiesRegistrar.class类实现了ImportBeanDefinitionRegistrar接口的类将会调用它的registerBeanDefinitions方法,向Spring容器中注册Bean定义
class EnableConfigurationPropertiesRegistrar implements ImportBeanDefinitionRegistrar {
@Override
public void registerBeanDefinitions(AnnotationMetadata metadata, BeanDefinitionRegistry registry) {
registerInfrastructureBeans(registry);
ConfigurationPropertiesBeanRegistrar beanRegistrar = new ConfigurationPropertiesBeanRegistrar(registry);
getTypes(metadata).forEach(beanRegistrar::register);
}
private Set> getTypes(AnnotationMetadata metadata) {
return metadata.getAnnotations().stream(EnableConfigurationProperties.class)
.flatMap((annotation) -> Arrays.stream(annotation.getClassArray(MergedAnnotation.VALUE)))
.filter((type) -> void.class != type).collect(Collectors.toSet());
}
@SuppressWarnings("deprecation")
static void registerInfrastructureBeans(BeanDefinitionRegistry registry) {
ConfigurationPropertiesBindingPostProcessor.register(registry);
ConfigurationPropertiesBeanDefinitionValidator.register(registry);
ConfigurationBeanFactoryMetadata.register(registry);
}
}
@ConfigurationProperties可以将外部配置文件（applicaition.properties中spring.redis下的配置）加载进来，填充对象的对应字段的数据，然后供其他Bean使用。
/**
* Configuration properties for Redis.
*
* @author Dave Syer
* @author Christoph Strobl
* @author Eddú Meléndez
* @author Marco Aust
* @author Mark Paluch
* @author Stephane Nicoll
* @since 1.0.0
*/
//指明spring.redis作为前缀
@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:[email protected]:6379
*/
private String url;
/**
* Redis server host.
*/
private String host = "localhost";
/**
* Login password of the redis server.
*/
private String password;
- RedisAutoConfiguration里配置了redisTemplate和stringRedisTemplate组件
- 使用@Import 注解导入了JedisConnectionConfiguration.class
- JedisConnectionConfiguration 类把JedisConnectionFactory注册到了bean，并且配置了jedisPoolConfig
private JedisClientConfiguration getJedisClientConfiguration(
ObjectProvider builderCustomizers) {
JedisClientConfigurationBuilder builder = applyProperties(JedisClientConfiguration.builder());
RedisProperties.Pool pool = getProperties().getJedis().getPool();
if (pool != null) {
applyPooling(pool, builder);
}
if (StringUtils.hasText(getProperties().getUrl())) {
customizeConfigurationFromUrl(builder);
}
builderCustomizers.orderedStream().forEach((customizer) -> customizer.customize(builder));
return builder.build();
}
private JedisPoolConfig jedisPoolConfig(RedisProperties.Pool pool) {
JedisPoolConfig config = new JedisPoolConfig();
config.setMaxTotal(pool.getMaxActive());
config.setMaxIdle(pool.getMaxIdle());
config.setMinIdle(pool.getMinIdle());
if (pool.getTimeBetweenEvictionRuns() != null) {
config.setTimeBetweenEvictionRunsMillis(pool.getTimeBetweenEvictionRuns().toMillis());
}
if (pool.getMaxWait() != null) {
config.setMaxWaitMillis(pool.getMaxWait().toMillis());
}
return config;
}