Disclaimer: This article is a blogger original article, shall not be reproduced without the bloggers allowed. https://blog.csdn.net/yj1499945/article/details/86776329
The code is based on spring boot 1.5.9
The first is to start class
@SpringBootApplication
@EnableTransactionManagement(proxyTargetClass = true)
@MapperScan(basePackages = {"com.frame.springboot.dao", "com.frame.springboot.base"})
public class SpringbootApplication {
public static void main(String[] args) {
// SpringApplication.run(SpringbootApplication.class, args);
SpringApplication app = new SpringApplication(SpringbootApplication.class);
app.addListeners(new MyApplicationStartedEventListener());
app.run(args);
}
static class MyApplicationStartedEventListener implements ApplicationListener<ApplicationStartedEvent> {
private Logger logger = LoggerFactory.getLogger(MyApplicationStartedEventListener.class);
@Override
public void onApplicationEvent(ApplicationStartedEvent event) {
SpringApplication app = event.getSpringApplication();
app.setBannerMode(Banner.Mode.OFF);// 不显示banner信息
logger.info("==MyApplicationStartedEventListener==");
}
}
}Here I signed up for a listener
Then look at the run method
public ConfigurableApplicationContext run(String... args) {
StopWatch stopWatch = new StopWatch();
stopWatch.start();
ConfigurableApplicationContext context = null;
FailureAnalyzers analyzers = null;
this.configureHeadlessProperty();
SpringApplicationRunListeners listeners = this.getRunListeners(args);
listeners.starting();
try {
ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
ConfigurableEnvironment environment = this.prepareEnvironment(listeners, applicationArguments);
Banner printedBanner = this.printBanner(environment);
context = this.createApplicationContext();
new FailureAnalyzers(context);
this.prepareContext(context, environment, listeners, applicationArguments, printedBanner);
this.refreshContext(context);
this.afterRefresh(context, applicationArguments);
listeners.finished(context, (Throwable)null);
stopWatch.stop();
if (this.logStartupInfo) {
(new StartupInfoLogger(this.mainApplicationClass)).logStarted(this.getApplicationLog(), stopWatch);
}
return context;
} catch (Throwable var9) {
this.handleRunFailure(context, listeners, (FailureAnalyzers)analyzers, var9);
throw new IllegalStateException(var9);
}
}You can see it is to listen to events by getRunListeners, enter getRunListeners method
private SpringApplicationRunListeners getRunListeners(String[] args) {
Class<?>[] types = new Class[]{SpringApplication.class, String[].class};
return new SpringApplicationRunListeners(logger, this.getSpringFactoriesInstances(SpringApplicationRunListener.class, types, this, args));
}Here only see initialize a listener class specific operation in which getSpringFactoriesInstances
private <T> Collection<? extends T> getSpringFactoriesInstances(Class<T> type, Class<?>[] parameterTypes, Object... args) {
ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
Set<String> names = new LinkedHashSet(SpringFactoriesLoader.loadFactoryNames(type, classLoader));
List<T> instances = this.createSpringFactoriesInstances(type, parameterTypes, classLoader, args, names);
AnnotationAwareOrderComparator.sort(instances);
return instances;
}Here the most important discovery method is loadFactoryNames and createSpringFactoriesInstances, followed by one by one, in terms of
The first is loadFactoryNames
public static List<String> loadFactoryNames(Class<?> factoryClass, ClassLoader classLoader) {
String factoryClassName = factoryClass.getName();
try {
Enumeration<URL> urls = classLoader != null ? classLoader.getResources("META-INF/spring.factories") : ClassLoader.getSystemResources("META-INF/spring.factories");
ArrayList result = new ArrayList();
while(urls.hasMoreElements()) {
URL url = (URL)urls.nextElement();
Properties properties = PropertiesLoaderUtils.loadProperties(new UrlResource(url));
String factoryClassNames = properties.getProperty(factoryClassName);
result.addAll(Arrays.asList(StringUtils.commaDelimitedListToStringArray(factoryClassNames)));
}
return result;
} catch (IOException var8) {
throw new IllegalArgumentException("Unable to load [" + factoryClass.getName() + "] factories from location [" + "META-INF/spring.factories" + "]", var8);
}
}This can be seen to be treated like spring.factories read listener is EventPublishingRunListener, the current processing class is just a string name has not been reflected get a real object.
This is the configuration file spring.factories
# PropertySource Loaders
org.springframework.boot.env.PropertySourceLoader=\
org.springframework.boot.env.PropertiesPropertySourceLoader,\
org.springframework.boot.env.YamlPropertySourceLoader
# Run Listeners
org.springframework.boot.SpringApplicationRunListener=\
org.springframework.boot.context.event.EventPublishingRunListener
# Application Context Initializers
org.springframework.context.ApplicationContextInitializer=\
org.springframework.boot.context.ConfigurationWarningsApplicationContextInitializer,\
org.springframework.boot.context.ContextIdApplicationContextInitializer,\
org.springframework.boot.context.config.DelegatingApplicationContextInitializer,\
org.springframework.boot.context.embedded.ServerPortInfoApplicationContextInitializer
# Application Listeners
org.springframework.context.ApplicationListener=\
org.springframework.boot.ClearCachesApplicationListener,\
org.springframework.boot.builder.ParentContextCloserApplicationListener,\
org.springframework.boot.context.FileEncodingApplicationListener,\
org.springframework.boot.context.config.AnsiOutputApplicationListener,\
org.springframework.boot.context.config.ConfigFileApplicationListener,\
org.springframework.boot.context.config.DelegatingApplicationListener,\
org.springframework.boot.liquibase.LiquibaseServiceLocatorApplicationListener,\
org.springframework.boot.logging.ClasspathLoggingApplicationListener,\
org.springframework.boot.logging.LoggingApplicationListener
# Environment Post Processors
org.springframework.boot.env.EnvironmentPostProcessor=\
org.springframework.boot.cloud.CloudFoundryVcapEnvironmentPostProcessor,\
org.springframework.boot.env.SpringApplicationJsonEnvironmentPostProcessor
# Failure Analyzers
org.springframework.boot.diagnostics.FailureAnalyzer=\
org.springframework.boot.diagnostics.analyzer.BeanCurrentlyInCreationFailureAnalyzer,\
org.springframework.boot.diagnostics.analyzer.BeanNotOfRequiredTypeFailureAnalyzer,\
org.springframework.boot.diagnostics.analyzer.BindFailureAnalyzer,\
org.springframework.boot.diagnostics.analyzer.ConnectorStartFailureAnalyzer,\
org.springframework.boot.diagnostics.analyzer.NoUniqueBeanDefinitionFailureAnalyzer,\
org.springframework.boot.diagnostics.analyzer.PortInUseFailureAnalyzer,\
org.springframework.boot.diagnostics.analyzer.ValidationExceptionFailureAnalyzer
# FailureAnalysisReporters
org.springframework.boot.diagnostics.FailureAnalysisReporter=\
org.springframework.boot.diagnostics.LoggingFailureAnalysisReporter
createSpringFactoriesInstances create an instance
private <T> List<T> createSpringFactoriesInstances(Class<T> type, Class<?>[] parameterTypes, ClassLoader classLoader, Object[] args, Set<String> names) {
List<T> instances = new ArrayList(names.size());
Iterator var7 = names.iterator();
while(var7.hasNext()) {
String name = (String)var7.next();
try {
Class<?> instanceClass = ClassUtils.forName(name, classLoader);
Assert.isAssignable(type, instanceClass);
Constructor<?> constructor = instanceClass.getDeclaredConstructor(parameterTypes);
T instance = BeanUtils.instantiateClass(constructor, args);
instances.add(instance);
} catch (Throwable var12) {
throw new IllegalArgumentException("Cannot instantiate " + type + " : " + name, var12);
}
}
return instances;
}
Here is to be the default initialization EventPublishingRunListener place, we look at the class constructor EventPublishingRunListener
public EventPublishingRunListener(SpringApplication application, String[] args) {
this.application = application;
this.args = args;
this.initialMulticaster = new SimpleApplicationEventMulticaster();
Iterator var3 = application.getListeners().iterator();
while(var3.hasNext()) {
ApplicationListener<?> listener = (ApplicationListener)var3.next();
this.initialMulticaster.addApplicationListener(listener);
}
}Before we customized a listener, you can see where the listener will customize the default listener and all added to the inside, the default listener in spring.factories there.
Now the SpringApplicationRunListeners initialization say clearly, talk about what's next start will be the time to do (here only analyzed for ApplicationStartedEvent event).
1.5.9 In the event of a commonly shared 5
ApplicationEnvironmentPreparedEvent
ApplicationPreparedEvent
ApplicationReadyEvent
ApplicationFailedEvent
ApplicationStartingEvent
Then start the analysis
There is a line in the run method
listeners.starting();Next we look at some of what he did.
public void starting() {
Iterator var1 = this.listeners.iterator();
while(var1.hasNext()) {
SpringApplicationRunListener listener = (SpringApplicationRunListener)var1.next();
listener.starting();
}
}For each listener objects which are launched, the listener object is essentially EventPublishingRunListener object.
public void starting() {
this.initialMulticaster.multicastEvent(new ApplicationStartedEvent(this.application, this.args));
}
Can be seen starting from here, EventPublishingRunListener starts operation to internal instantiated SimpleApplicationEventMulticaster do.
public void multicastEvent(final ApplicationEvent event, ResolvableType eventType) {
ResolvableType type = eventType != null ? eventType : this.resolveDefaultEventType(event);
Iterator var4 = this.getApplicationListeners(event, type).iterator();
while(var4.hasNext()) {
final ApplicationListener<?> listener = (ApplicationListener)var4.next();
Executor executor = this.getTaskExecutor();
if (executor != null) {
executor.execute(new Runnable() {
public void run() {
SimpleApplicationEventMulticaster.this.invokeListener(listener, event);
}
});
} else {
this.invokeListener(listener, event);
}
}
}It will be notified to a specific area to make a specific thread pool.