利用 Spring 工廠加載機制,實例化 ApplicationContextInitializer 實現類,並排序對象集合。
關鍵方法
privateCollectiongetSpringFactoriesInstances(Classtype, Class[] parameterTypes, Object... args) { ClassLoader classLoader = Thread.currentThread().getContextClassLoader(); // Use names and ensure unique to protect against duplicates Setnames = new LinkedHashSet<>( SpringFactoriesLoader.loadFactoryNames(type, classLoader)); Listinstances = createSpringFactoriesInstances(type, parameterTypes, classLoader, args, names); AnnotationAwareOrderComparator.sort(instances); return instances; }
技術實現步驟
實現類: org.springframework.core.io.support.SpringFactoriesLoader
配置資源: META-INF/spring.factories
排序: AnnotationAwareOrderComparator#sort
自定義初始化器
編寫類實現ApplicationContextInitializer接口
有兩種指定順序的方法,第一種:類上加註解@Order(Ordered.HIGHEST_PRECEDENCE),第二種則是實現Ordered接口
@Order(Ordered.HIGHEST_PRECEDENCE) public class HelloWorldApplicationContextInitializerimplements ApplicationContextInitializer{ @Override public void initialize(C applicationContext) { System.out.println("ConfigurableApplicationContext.id = "+ applicationContext.getId()); } }
public class AfterHelloWorldApplicationContextInitializer implements ApplicationContextInitializer, Ordered { @Override public void initialize(ConfigurableApplicationContext applicationContext) { System.out.println("After application.id = " + applicationContext.getId()); } @Override public int getOrder() { return Ordered.LOWEST_PRECEDENCE; } }
在spring.properties中配置
# ApplicationContextInitializer
org.springframework.context.ApplicationContextInitializer=
com.imooc.diveinspringboot.context.AfterHelloWorldApplicationContextInitializer,
com.imooc.diveinspringboot.context.HelloWorldApplicationContextInitializer
[madbeef ] SpringBoot上下文初始器加載過程詳解已經有216次圍觀