基本流程图

image.png

TomcatServletWebServerFactory的getWebServer

前面我们获取到了TomcatServletWebServerFactory，现在就要创建了，创建TomcatWebServer，里面会进行初始化，这里的方法就不多讲了，是关于tomcat的一些组件的设置和启动，有兴趣可以自己研究下，我们重点关注springmvc这边的。

@Override
    public WebServer getWebServer(ServletContextInitializer... initializers) {
        if (this.disableMBeanRegistry) {
            Registry.disableRegistry();
        }
        Tomcat tomcat = new Tomcat();
        File baseDir = (this.baseDirectory != null) ? this.baseDirectory : createTempDir("tomcat");
        tomcat.setBaseDir(baseDir.getAbsolutePath());
        Connector connector = new Connector(this.protocol);
        connector.setThrowOnFailure(true);
        tomcat.getService().addConnector(connector);
        customizeConnector(connector);
        tomcat.setConnector(connector);
        tomcat.getHost().setAutoDeploy(false);
        configureEngine(tomcat.getEngine());
        for (Connector additionalConnector : this.additionalTomcatConnectors) {
            tomcat.getService().addConnector(additionalConnector);
        }
        prepareContext(tomcat.getHost(), initializers);
        return getTomcatWebServer(tomcat);
    }

    protected TomcatWebServer getTomcatWebServer(Tomcat tomcat) {
        return new TomcatWebServer(tomcat, getPort() >= 0);
    }
    public TomcatWebServer(Tomcat tomcat, boolean autoStart) {
        Assert.notNull(tomcat, "Tomcat Server must not be null");
        this.tomcat = tomcat;
        this.autoStart = autoStart;
        initialize();
    }

ServletWebServerApplicationContext的finishRefresh

完成刷新后，就启动了服务器，并发出ServletWebServerInitializedEvent事件：

image.png

DispatcherServlet初始化

流程图参考

image.png

第一次来请求的时候会进行初始化，调用initStrategies方法，其实就是把需要的组件都获取到：

protected void initStrategies(ApplicationContext context) {
        initMultipartResolver(context);//上传文件
        initLocaleResolver(context);//本地化
        initThemeResolver(context);//主题
        initHandlerMappings(context);//映射器
        initHandlerAdapters(context);//处理器适配器
        initHandlerExceptionResolvers(context);//异常处理
        initRequestToViewNameTranslator(context);//视图名转换
        initViewResolvers(context);//视图解析
        initFlashMapManager(context);//重定向保存数据
    }

内部其实很多都是一样的形式，我拿两个分析下：

initMultipartResolver

首先会获取名字为multipartResolver的实例，如果不存在就为null。

public static final String MULTIPART_RESOLVER_BEAN_NAME = "multipartResolver";

private void initMultipartResolver(ApplicationContext context) {
        try {
            this.multipartResolver = context.getBean(MULTIPART_RESOLVER_BEAN_NAME, MultipartResolver.class);
            if (logger.isTraceEnabled()) {
                logger.trace("Detected " + this.multipartResolver);
            }
            else if (logger.isDebugEnabled()) {
                logger.debug("Detected " + this.multipartResolver.getClass().getSimpleName());
            }
        }
        catch (NoSuchBeanDefinitionException ex) {
            // Default is no multipart resolver.
            this.multipartResolver = null;
            if (logger.isTraceEnabled()) {
                logger.trace("No MultipartResolver '" + MULTIPART_RESOLVER_BEAN_NAME + "' declared");
            }
        }
    }