spring boot 自动装配 自己小结
@SpringBootApplication
||
||点击进来发现
||
\/
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@SpringBootConfiguration //说明这是一个自动配置类
@EnableAutoConfiguration//自动配置类
@ComponentScan(excludeFilters = {
@Filter(type = FilterType.CUSTOM, classes = TypeExcludeFilter.class),
@Filter(type = FilterType.CUSTOM, classes = AutoConfigurationExcludeFilter.class) })
||
||点击进来发现
||
\/
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@AutoConfigurationPackage //自动配置包
@Import(AutoConfigurationImportSelector.class) //自动配置导入选择器 ||
||点击进来发现
||
\/
//导入这个类
public class AutoConfigurationImportSelector implements DeferredImportSelector, BeanClassLoaderAware,
ResourceLoaderAware, BeanFactoryAware, EnvironmentAware, Ordered {
private static final AutoConfigurationEntry EMPTY_ENTRY = new AutoConfigurationEntry();
private static final String[] NO_IMPORTS = {
};
private static final Log logger = LogFactory.getLog(AutoConfigurationImportSelector.class);
private static final String PROPERTY_NAME_AUTOCONFIGURE_EXCLUDE = "spring.autoconfigure.exclude";
private ConfigurableListableBeanFactory beanFactory;
private Environment environment;
private ClassLoader beanClassLoader;
private ResourceLoader resourceLoader;
@Override
public String[] selectImports(AnnotationMetadata annotationMetadata) {
if (!isEnabled(annotationMetadata)) {
return NO_IMPORTS;
}
AutoConfigurationMetadata autoConfigurationMetadata = AutoConfigurationMetadataLoader
.loadMetadata(this.beanClassLoader);
AutoConfigurationEntry autoConfigurationEntry = getAutoConfigurationEntry(autoConfigurationMetadata,
annotationMetadata); //获取自动配置条目，进入这个方法
return StringUtils.toStringArray(autoConfigurationEntry.getConfigurations());
}
进入getAutoConfigurationEntry () 方法
/**
* Return the {@link AutoConfigurationEntry} based on the {@link AnnotationMetadata}
* of the importing {@link Configuration @Configuration} class.
* @param autoConfigurationMetadata the auto-configuration metadata
* @param annotationMetadata the annotation metadata of the configuration class
* @return the auto-configurations that should be imported
*/
protected AutoConfigurationEntry getAutoConfigurationEntry(AutoConfigurationMetadata autoConfigurationMetadata,
AnnotationMetadata annotationMetadata) {
if (!isEnabled(annotationMetadata)) {
return EMPTY_ENTRY;
}
AnnotationAttributes attributes = getAttributes(annotationMetadata);
List<String> configurations = getCandidateConfigurations(annotationMetadata, attributes);//获取候选配置
configurations = removeDuplicates(configurations);//是否有重复的
Set<String> exclusions = getExclusions(annotationMetadata, attributes);//排除不用的自动配置类
checkExcludedClasses(configurations, exclusions);
configurations.removeAll(exclusions);//排除
configurations = filter(configurations, autoConfigurationMetadata); //判断有没有导入jar包
fireAutoConfigurationImportEvents(configurations, exclusions);
return new AutoConfigurationEntry(configurations, exclusions);
}
点击进入 getCandidateConfigurations () 候选配置方法
/**
* Return the auto-configuration class names that should be considered. By default
* this method will load candidates using {@link SpringFactoriesLoader} with
* {@link #getSpringFactoriesLoaderFactoryClass()}.
* @param metadata the source metadata
* @param attributes the {@link #getAttributes(AnnotationMetadata) annotation
* attributes}
* @return a list of candidate configurations
*/
protected List<String> getCandidateConfigurations(AnnotationMetadata metadata, AnnotationAttributes attributes) {
List<String> configurations =
//加载工厂名称 loadFactoryNames
SpringFactoriesLoader.loadFactoryNames(getSpringFactoriesLoaderFactoryClass(),
getBeanClassLoader());//传入2个参数 一个加载自动装配类 ，还有类加载器
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;
}
点击进入 loadFactoryNames() 会加载配置的 META-INF/spring.factories 中的自动装配类
private static Map<String, List<String>> loadSpringFactories(@Nullable ClassLoader classLoader) {
MultiValueMap<String, String> result = cache.get(classLoader);//第一次查询将全部全部放到缓存中 MultiValueMap 结构 key 多个value
if (result != null) {
return result;
}
try {
Enumeration<URL> 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);
}
}
//返回spi 方式