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

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.tamguo</groupId>
  <artifactId>tamguo-test</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.3.RELEASE</version>
        <relativePath /> <!-- lookup parent from repository -->
    </parent>
    
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
    </dependencies>
    
</project>

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