spring boot 2.0 | 怎样启动内置的tomcat

spring boot 2.0 | 怎样启动内置的tomcat

标签（空格分隔）： springboot

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本文讲解springboot2.0在什么时候和用什么方式启动的内置tomcat。
首先创建一个简单的maven模板工程

pom.xml

4.0.0
com.tamguo
tamguo-test
0.0.1-SNAPSHOT

org.springframework.boot
spring-boot-starter-parent
2.0.3.RELEASE

org.springframework.boot
spring-boot-starter-web

boot-starter-web是包含了spring-web，spring-webmvc，spring-tomcat-start 和springboot启动的引导类。

然后在src下面创建一个java启动类

@SpringBootApplication
public class TamguoApplication {

public static void main(String[] args) {
new SpringApplicationBuilder(TamguoApplication.class).run(args);
}

}

@SpringBootApplication 它包括三个注解：

@Configuration：表示将该类作用springboot配置文件类。
@EnableAutoConfiguration:表示程序启动时，自动加载springboot默认的配置。
@ComponentScan:表示程序启动是，自动扫描当前包及子包下所有类。

启动项目我们关注下项目日志

2018-08-29 11:55:10.127 INFO 51996 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8080 (http) with context path ''

找到类TomcatWebServer

private void initialize() throws WebServerException {
TomcatWebServer.logger
.info("Tomcat initialized with port(s): " + getPortsDescription(false));
synchronized (this.monitor) {
try {
addInstanceIdToEngineName();

Context context = findContext();
context.addLifecycleListener((event) -> {
if (context.equals(event.getSource())
&& Lifecycle.START_EVENT.equals(event.getType())) {
// Remove service connectors so that protocol binding doesn't
// happen when the service is started.
removeServiceConnectors();
}
});

// Start the server to trigger initialization listeners
this.tomcat.start();

// We can re-throw failure exception directly in the main thread
rethrowDeferredStartupExceptions();

try {
ContextBindings.bindClassLoader(context, context.getNamingToken(),
getClass().getClassLoader());
}
catch (NamingException ex) {
// Naming is not enabled. Continue
}

// Unlike Jetty, all Tomcat threads are daemon threads. We create a
// blocking non-daemon to stop immediate shutdown
startDaemonAwaitThread();
}
catch (Exception ex) {
stopSilently();
throw new WebServerException("Unable to start embedded Tomcat", ex);
}
}
}

看到this.tomcat.start();就是启动tomcat了。它是在刷新spring容器执行的启动tomcat。

@Override
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
// Prepare this context for refreshing.
prepareRefresh();

// Tell the subclass to refresh the internal bean factory.
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

// Prepare the bean factory for use in this context.
prepareBeanFactory(beanFactory);

try {
// Allows post-processing of the bean factory in context subclasses.
postProcessBeanFactory(beanFactory);

// Invoke factory processors registered as beans in the context.
invokeBeanFactoryPostProcessors(beanFactory);

// Register bean processors that intercept bean creation.
registerBeanPostProcessors(beanFactory);

// Initialize message source for this context.
initMessageSource();

// Initialize event multicaster for this context.
initApplicationEventMulticaster();

// Initialize other special beans in specific context subclasses.
onRefresh();

// Check for listener beans and register them.
registerListeners();

// Instantiate all remaining (non-lazy-init) singletons.
finishBeanFactoryInitialization(beanFactory);

// Last step: publish corresponding event.
finishRefresh();
}

catch (BeansException ex) {
if (logger.isWarnEnabled()) {
logger.warn("Exception encountered during context initialization - " +
"cancelling refresh attempt: " + ex);
}

// Destroy already created singletons to avoid dangling resources.
destroyBeans();

// Reset 'active' flag.
cancelRefresh(ex);

// Propagate exception to caller.
throw ex;
}

finally {
// Reset common introspection caches in Spring's core, since we
// might not ever need metadata for singleton beans anymore...
resetCommonCaches();
}
}
}

onRefresh()方法启动tomcat

探果网