做网站的天空网,兰州网站的优化,微信社区官网,军事网报名入口简介
其实spring启动步骤中最早可以进行扩展的是实现ApplicationContextInitializer接口。来看看这个接口的注释。
package org.springframework.context;/*** Callback interface for initializing a Spring {link ConfigurableApplicationContext}* prior to being {linkpl…简介
其实spring启动步骤中最早可以进行扩展的是实现ApplicationContextInitializer接口。来看看这个接口的注释。
package org.springframework.context;/*** Callback interface for initializing a Spring {link ConfigurableApplicationContext}* prior to being {linkplain ConfigurableApplicationContext#refresh() refreshed}.** pTypically used within web applications that require some programmatic initialization* of the application context. For example, registering property sources or activating* profiles against the {linkplain ConfigurableApplicationContext#getEnvironment()* contexts environment}. See {code ContextLoader} and {code FrameworkServlet} support* for declaring a contextInitializerClasses context-param and init-param, respectively.** p{code ApplicationContextInitializer} processors are encouraged to detect* whether Springs {link org.springframework.core.Ordered Ordered} interface has been* implemented or if the {link org.springframework.core.annotation.Order Order}* annotation is present and to sort instances accordingly if so prior to invocation.** author Chris Beams* since 3.1* param C the application context type* see org.springframework.web.context.ContextLoader#customizeContext* see org.springframework.web.context.ContextLoader#CONTEXT_INITIALIZER_CLASSES_PARAM* see org.springframework.web.servlet.FrameworkServlet#setContextInitializerClasses* see org.springframework.web.servlet.FrameworkServlet#applyInitializers*/
FunctionalInterface
public interface ApplicationContextInitializerC extends ConfigurableApplicationContext {/*** Initialize the given application context.* param applicationContext the application to configure*/void initialize(C applicationContext);}简要的说明一下有这么几点:
实现这个接口之后它的initialize方法会在容器ConfigurableApplicationContext刷新之前触发。它通常用于在容器初始化之前进行一些程序上的操作比如说注册一些环境变量或者读取一些配置文件。它可以使用Order指定优先级
实现方式
它有三种实现方式:
通过SPI机制实现在resources/META-INF/spring.factories中定义如下内容: org.springframework.context.ApplicationContextInitializercom.alone.spring.aop.demo.config.ContextInitializerTest
/*** spring扩展点 ApplicationContextInitializer*/
Slf4j
public class ContextInitializerTest implements ApplicationContextInitializer {Overridepublic void initialize(ConfigurableApplicationContext applicationContext) {log.info(ContextInitializerTest 开始加载);ConfigurableEnvironment environment applicationContext.getEnvironment();MapString, Object initMap new HashMap();initMap.put(20231116, This is init);MapPropertySource propertySource new MapPropertySource(ContextInitializerTest, initMap);environment.getPropertySources().addLast(propertySource);log.info(ContextInitializerTest 加载结束);}
}在application.yml中定义如下内容:
context:initializer:classes: com.alone.spring.aop.demo.config.YmlApplicationContextInitializerSlf4j
public class YmlApplicationContextInitializer implements ApplicationContextInitializer {Overridepublic void initialize(ConfigurableApplicationContext applicationContext) {log.info(这是yml的ApplicationContextInitializer);ConfigurableEnvironment environment applicationContext.getEnvironment();MapString, Object initMap new HashMap();initMap.put(20231116, YmlApplicationContextInitializer);MapPropertySource propertySource new MapPropertySource(ContextInitializerTest, initMap);environment.getPropertySources().addLast(propertySource);log.info(YmlApplicationContextInitializer 加载结束);}
}在启动类中进行注册:
public static void main(String[] args) {SpringApplication springApplication new SpringApplication(SpringbootApplication.class);springApplication.addInitializers(new MainFlagApplicationContextInitializer());springApplication.run();
}Component
Slf4j
public class MainFlagApplicationContextInitializer implements ApplicationContextInitializer {Overridepublic void initialize(ConfigurableApplicationContext applicationContext) {log.info(这是main的ApplicationContextInitializer);ConfigurableEnvironment environment applicationContext.getEnvironment();MapString, Object initMap new HashMap();initMap.put(20231116, MainFlagApplicationContextInitializer);MapPropertySource propertySource new MapPropertySource(ContextInitializerTest, initMap);environment.getPropertySources().addLast(propertySource);log.info(MainFlagApplicationContextInitializer 加载结束);}
}三者的加载顺序是: application.yml spring.factories 启动类
源码分析
从启动类的new SpringApplication(SpringbootApplication.class)开始分析:
public SpringApplication(ResourceLoader resourceLoader, Class?... primarySources) {this.resourceLoader resourceLoader;Assert.notNull(primarySources, PrimarySources must not be null);this.primarySources new LinkedHashSet(Arrays.asList(primarySources));this.webApplicationType WebApplicationType.deduceFromClasspath();this.bootstrapRegistryInitializers new ArrayList(getSpringFactoriesInstances(BootstrapRegistryInitializer.class));setInitializers((Collection) getSpringFactoriesInstances(ApplicationContextInitializer.class));setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));this.mainApplicationClass deduceMainApplicationClass();
}看到上面第8行源码266行中出现了ApplicationContextInitializer.class猜想它肯定是在读取相关的配置跟进去发现出现了下面这行。 这里是读取了spring.factories中的内容但看它的结果发现不止我们自定义的类一个说明springboot内置了一些ApplicationContextInitializer后续我们再看它们具体的作用这里先截图列出按下不表。 然后沿如下的调用栈可以找到initializer.initialize(context);这一行调用ApplicationContextInitializer的语句。 ● springApplication.run() ● run:306, SpringApplication (org.springframework.boot) ● prepareContext:383, SpringApplication (org.springframework.boot) ● applyInitializers:614, SpringApplication (org.springframework.boot)
框起来的方法会对所有的initializer进行排序排序后的结果见左边。 在执行到DelegatingApplicationContextInitializer时会去读取环境中的context.initializer.classes也就是application.yml中配置的内容执行。所以会先执行yml配置的initializer.
以上总结一下是这样的:
大致调用的流程图是:
系统内置初始化类
最后我们来看看上面提到的系统内置的初始化类都有些什么作用。
SharedMetadataReaderFactoryContextInitializer
Override
public void initialize(ConfigurableApplicationContext applicationContext) {BeanFactoryPostProcessor postProcessor new CachingMetadataReaderFactoryPostProcessor(applicationContext);applicationContext.addBeanFactoryPostProcessor(postProcessor);
}初始化了一个CachingMetadataReaderFactoryPostProcessor至容器中
DelegatingApplicationContextInitializer
Override
public void initialize(ConfigurableApplicationContext context) {ConfigurableEnvironment environment context.getEnvironment();ListClass? initializerClasses getInitializerClasses(environment);if (!initializerClasses.isEmpty()) {applyInitializerClasses(context, initializerClasses);}
}执行context.initializer.classes配置的initializer。
ContextIdApplicationContextInitializer
Override
public void initialize(ConfigurableApplicationContext applicationContext) {ContextId contextId getContextId(applicationContext);applicationContext.setId(contextId.getId());applicationContext.getBeanFactory().registerSingleton(ContextId.class.getName(), contextId);
}private ContextId getContextId(ConfigurableApplicationContext applicationContext) {ApplicationContext parent applicationContext.getParent();if (parent ! null parent.containsBean(ContextId.class.getName())) {return parent.getBean(ContextId.class).createChildId();}return new ContextId(getApplicationId(applicationContext.getEnvironment()));
}private String getApplicationId(ConfigurableEnvironment environment) {String name environment.getProperty(spring.application.name);return StringUtils.hasText(name) ? name : application;
}设置容器的id值取自spring.application.name配置默认是application
ConditionEvaluationReportLoggingListener
Override
public void initialize(ConfigurableApplicationContext applicationContext) {this.applicationContext applicationContext;applicationContext.addApplicationListener(new ConditionEvaluationReportListener());if (applicationContext instanceof GenericApplicationContext) {// Get the report early in case the context fails to loadthis.report ConditionEvaluationReport.get(this.applicationContext.getBeanFactory());}
}注册了一个ConditionEvaluationReportListener
RestartScopeInitializer
Override
public void initialize(ConfigurableApplicationContext applicationContext) {applicationContext.getBeanFactory().registerScope(restart, new RestartScope());
}自动重启相关。
ConfigurationWarningsApplicationContextInitializer
Override
public void initialize(ConfigurableApplicationContext context) {context.addBeanFactoryPostProcessor(new ConfigurationWarningsPostProcessor(getChecks()));
}初始化一个ConfigurationWarningsPostProcessor用于记录公共的容器配置错误信息。
RSocketPortInfoApplicationContextInitializer
Override
public void initialize(ConfigurableApplicationContext applicationContext) {applicationContext.addApplicationListener(new Listener(applicationContext));
}增加了一个监听器用于监听RSockerServer的端口是否正常。
ServerPortInfoApplicationContextInitializer
/*** {link ApplicationContextInitializer} that sets {link Environment} properties for the* ports that {link WebServer} servers are actually listening on. The property* {literal local.server.port} can be injected directly into tests using* {link Value Value} or obtained via the {link Environment}.* p* If the {link WebServerInitializedEvent} has a* {link WebServerApplicationContext#getServerNamespace() server namespace} , it will be* used to construct the property name. For example, the management actuator context* will have the property name {literal local.management.port}.* p* Properties are automatically propagated up to any parent context.** author Dave Syer* author Phillip Webb* since 2.0.0*/Override
public void initialize(ConfigurableApplicationContext applicationContext) {applicationContext.addApplicationListener(this);
}向容器中增加一个监听器用于检测WebServer的端口是否正常监听。
参考资料
SpringBoot系统初始化器使用及源码解析ApplicationContextInitializer跟我一起阅读SpringBoot源码九——初始化执行器Springboot扩展点之ApplicationContextInitializer
