DispatcherServlet

初始化时机

默认是第一次请求的时候进行初始化

可以通过配置文件spring.mvc.servlet.load-on-startup=1 开启容器启动的时候即初始化

新增配置WebConfig


@Configuration
@ComponentScan
@PropertySource("classpath:application.properties")
@EnableConfigurationProperties({WebMvcProperties.class, ServerProperties.class})
public class WebConfig {
    // ⬅️内嵌 web 容器工厂
    @Bean
    public TomcatServletWebServerFactory tomcatServletWebServerFactory(ServerProperties serverProperties) {
        return new TomcatServletWebServerFactory(serverProperties.getPort());
    }

    // ⬅️创建 DispatcherServlet
    @Bean
    public DispatcherServlet dispatcherServlet() {
        return new DispatcherServlet();
    }

}


@Controller
public class Controller1 {

    private static final Logger log = LoggerFactory.getLogger(Controller1.class);

    @GetMapping("/test1")
    public ModelAndView test1() throws Exception {
        log.debug("test1()");
        return null;
    }

启动容器


AnnotationConfigServletWebServerApplicationContext context =
                new AnnotationConfigServletWebServerApplicationContext(WebConfig.class);

发现没有DispatcherServlet初始化的日志

访问localhost:8080/test1 接口后开始打印初始化日志

在配置类增加DispatcherServletRegistrationBean 配置文件增加 spring.mvc.servlet.load-on-startup = 1（只要大于0即可，数字大小决定顺序）之后，容器启动后自动初始化DispatcherServlet


@Configuration
@ComponentScan
@PropertySource("classpath:application.properties")
@EnableConfigurationProperties({WebMvcProperties.class, ServerProperties.class})
public class WebConfig {
    // ⬅️内嵌 web 容器工厂
    @Bean
    public TomcatServletWebServerFactory tomcatServletWebServerFactory(ServerProperties serverProperties) {
        return new TomcatServletWebServerFactory(serverProperties.getPort());
    }

    // ⬅️创建 DispatcherServlet
    @Bean
    public DispatcherServlet dispatcherServlet() {
        return new DispatcherServlet();
    }

    // ⬅️注册 DispatcherServlet, Spring MVC 的入口
    @Bean
    public DispatcherServletRegistrationBean dispatcherServletRegistrationBean(
            DispatcherServlet dispatcherServlet, WebMvcProperties webMvcProperties) {
        DispatcherServletRegistrationBean registrationBean = new DispatcherServletRegistrationBean(dispatcherServlet, "/");
        registrationBean.setLoadOnStartup(webMvcProperties.getServlet().getLoadOnStartup());
        return registrationBean;
    }


}

初始化流程

DispatcherServlet 的初始化代码


/**
	 * This implementation calls {@link #initStrategies}.
	 */
	@Override
	protected void onRefresh(ApplicationContext context) {
		initStrategies(context);
	}

  /**
	 * Initialize the strategy objects that this servlet uses.
	 * <p>May be overridden in subclasses in order to initialize further strategy objects.
	 */
	protected void initStrategies(ApplicationContext context) {
		initMultipartResolver(context);//初始化文件上传解析器
		initLocaleResolver(context);//本地化信息国家地区语言
		initThemeResolver(context);
		initHandlerMappings(context);//路径映射器
		initHandlerAdapters(context);//针对不同controller的适配器
		initHandlerExceptionResolvers(context);//异常处理器
		initRequestToViewNameTranslator(context);
		initViewResolvers(context);
		initFlashMapManager(context);
	}

initHandlerMappings

DispatcherServlet.properties 提供默认配置