看那个人好像一条狗-------------------------------------By 周星星
首先来看事件监听的定义的SpringApplicationRunListener,用户可以通过这个接口实现自己的自定义流程在SpringApplication启动过程中,现在我们来看看SpringApplicationRunListener的主要结构,这个接口主要定义了5个方法，包含了SpringApplication启动流程一系列事件
import org.springframework.context.ApplicationContext;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.core.env.ConfigurableEnvironment;
import org.springframework.core.io.support.SpringFactoriesLoader;
/**
* Listener for the {@link SpringApplication} {@code run} method.
* {@link SpringApplicationRunListener}s are loaded via the {@link SpringFactoriesLoader}
* and should declare a public constructor that accepts a {@link SpringApplication}
* instance and a {@code String[]} of arguments. A new
* {@link SpringApplicationRunListener} instance will be created for each run.
*
* @author Phillip Webb
* @author Dave Syer
*/
public interface SpringApplicationRunListener {
/**
* Called immediately when the run method has first started. Can be used for very
* early initialization.
*SpringApplication运行run方法时立即调用此方法，可以用户非常早期的初始化工作
*/
void starting();
/**
* Called once the environment has been prepared, but before the
* {@link ApplicationContext} has been created.
* @param environment the environment
* Environment准备好后，并且ApplicationContext创建之前调用
*/
void environmentPrepared(ConfigurableEnvironment environment);
/**
* Called once the {@link ApplicationContext} has been created and prepared, but
* before sources have been loaded.
* @param context the application context
* ApplicationContext创建好后立即调用
*/
void contextPrepared(ConfigurableApplicationContext context);
/**
* Called once the application context has been loaded but before it has been
* refreshed.
* @param context the application context
* ApplicationContext加载完成，在refresh之前调用
*/
void contextLoaded(ConfigurableApplicationContext context);
/**
* Called immediately before the run method finishes.
* @param context the application context or null if a failure occurred before the
* context was created
* @param exception any run exception or null if run completed successfully.
* 当run方法结束之前调用
*/
void finished(ConfigurableApplicationContext context, Throwable exception);
}
SpringBoot通过读取spring.factories文件通过反射的机制获取SpringApplicationRunListener的实现类
/**
* Run the Spring application, creating and refreshing a new
* {@link ApplicationContext}.
* @param args the application arguments (usually passed from a Java main method)
* @return a running {@link ApplicationContext}
*/
public ConfigurableApplicationContext run(String... args) {
StopWatch stopWatch = new StopWatch();
stopWatch.start();
ConfigurableApplicationContext context = null;
Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList<>();
configureHeadlessProperty();
SpringApplicationRunListeners listeners = getRunListeners(args);
listeners.starting();
try {
ApplicationArguments applicationArguments = new DefaultApplicationArguments(
args);
ConfigurableEnvironment environment = prepareEnvironment(listeners,
applicationArguments);
configureIgnoreBeanInfo(environment);
Banner printedBanner = printBanner(environment);
context = createApplicationContext();
exceptionReporters = getSpringFactoriesInstances(
SpringBootExceptionReporter.class,
new Class[] { ConfigurableApplicationContext.class }, context);
prepareContext(context, environment, listeners, applicationArguments,
printedBanner);
refreshContext(context);
afterRefresh(context, applicationArguments);
listeners.finished(context, null);
stopWatch.stop();
if (this.logStartupInfo) {
new StartupInfoLogger(this.mainApplicationClass)
.logStarted(getApplicationLog(), stopWatch);
}
callRunners(context, applicationArguments);
return context;
}
catch (Throwable ex) {
handleRunFailure(context, listeners, exceptionReporters, ex);
throw new IllegalStateException(ex);
}
}
其中SpringApplicationRunListeners listeners = getRunListeners(args)就是springBoot获取SpringApplicationRunListener监听器核心代码，时序图如下
springbootlistener.png
