如何注册

1.注解+启动类扫描

@ServletComponentScan
@SpringBootApplication
public class SpringbootUploadApplication {
    public static void main(String[] args) {
        SpringApplication.run(SpringbootUploadApplication.class, args);
    }
}

@WebServlet(urlPatterns = "/my")
public class MyServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.err.println("MyServlet doGet");
        resp.getWriter().write("my");
    }
}
@WebFilter(urlPatterns = "/my")
public class MyFilter extends HttpFilter {
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        HttpServletRequest req = (HttpServletRequest) request;
        System.err.println("MyFilter doFilter");
        chain.doFilter(request,response);
    }
}
@WebListener
public class MyListener implements ServletContextListener {
    @Override
    public void contextInitialized(ServletContextEvent sce) {
        System.err.println("MyListener contextInitialized"+sce.getServletContext().getServerInfo());
    }
    @Override
    public void contextDestroyed(ServletContextEvent sce) {
    }
}

2.注册ServletRegistrationBean

还是这三个组件,不过把注解@WebServlet/@WebFilter/@WebListener去掉,自动扫描就失效了
取而代之配置类去注册

@Configuration
public class ServletConfig {
    @Bean
    public ServletRegistrationBean myServlet(){
        MyServlet myServlet = new MyServlet();
        return new ServletRegistrationBean(myServlet,"/my","/my02");
    }
    @Bean
    public FilterRegistrationBean myFilter(){
        MyFilter myFilter = new MyFilter();
        FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean(myFilter);
        filterRegistrationBean.setUrlPatterns(Arrays.asList("/my","/css/*"));
        return filterRegistrationBean;
    }
    @Bean
    public ServletListenerRegistrationBean myListener(){
        MyListener mySwervletContextListener = new MyListener();
        return new ServletListenerRegistrationBean(mySwervletContextListener);
    }
}

源码

先看看注册Bean的类图

感觉用不上,不想看源码蛋疼,硬着头皮早上写!干饭

SpringApplication#refreshContext
AnnotationConfigServletWebServerApplicationContext#refresh #onRefresh
TomcatServletWebServerFactory 创建tomcat服务器并start

下面就是tomcat流程

接下来就是异步任务

子类调用父类
public class StandardEngine extends ContainerBase implements Engine {
         @Override
    protected synchronized void startInternal() throws LifecycleException {
        // Log our server identification information
        if (log.isInfoEnabled()) {
            log.info(sm.getString("standardEngine.start", ServerInfo.getServerInfo()));
        }
        // Standard container startup
        super.startInternal();
    }   
}
父类方法逻辑
public abstract class ContainerBase extends LifecycleMBeanBase implements Container {
    @Override
    protected synchronized void startInternal() throws LifecycleException {
        // Start our subordinate components, if any
        logger = null;
        getLogger();
        Cluster cluster = getClusterInternal();
        if (cluster instanceof Lifecycle) {
            ((Lifecycle) cluster).start();
        }
        Realm realm = getRealmInternal();
        if (realm instanceof Lifecycle) {
            ((Lifecycle) realm).start();
        }
        // Start our child containers, if any
        Container children[] = findChildren();
        List<Future<Void>> results = new ArrayList<>();
        for (Container child : children) {
            results.add(startStopExecutor.submit(new StartChild(child)));
        }
        MultiThrowable multiThrowable = null;
        for (Future<Void> result : results) {
            try {
                result.get();
            } catch (Throwable e) {
                log.error(sm.getString("containerBase.threadedStartFailed"), e);
                if (multiThrowable == null) {
                    multiThrowable = new MultiThrowable();
                }
                multiThrowable.add(e);
            }
        }
        if (multiThrowable != null) {
            throw new LifecycleException(sm.getString("containerBase.threadedStartFailed"),
                    multiThrowable.getThrowable());
        }
        // Start the Valves in our pipeline (including the basic), if any
        if (pipeline instanceof Lifecycle) {
            ((Lifecycle) pipeline).start();
        }
        setState(LifecycleState.STARTING);
        // Start our thread
        if (backgroundProcessorDelay > 0) {
            monitorFuture = Container.getService(ContainerBase.this).getServer()
                    .getUtilityExecutor().scheduleWithFixedDelay(
                            new ContainerBackgroundProcessorMonitor(), 0, 60, TimeUnit.SECONDS);
        }
    }
}

然后其中一个异步任务就会执行以下逻辑,具体跟不到是哪里

StandardHost->异步->TomcatEmbeddedContext#start->#startInternal->

部分逻辑
public class StandardContext extends ContainerBase implements Context, NotificationEmitter {
    @Override
    protected synchronized void startInternal() throws LifecycleException {
        // Call ServletContainerInitializers
        for (Map.Entry<ServletContainerInitializer, Set<Class<?>>> entry :
                initializers.entrySet()) {
                try {
                    entry.getKey().onStartup(entry.getValue(),
                            getServletContext());
                } catch (ServletException e) {
                    log.error(sm.getString("standardContext.sciFail"), e);
                    ok = false;
                    break;
                }
          }
    }
}

class TomcatStarter implements ServletContainerInitializer {
    //有三个,见下图
    private final ServletContextInitializer[] initializers;
     @Override
    public void onStartup(Set<Class<?>> classes, ServletContext servletContext) throws ServletException {
        try {
            for (ServletContextInitializer initializer : this.initializers) {
                initializer.onStartup(servletContext);
            }
        }
        catch (Exception ex) {
            this.startUpException = ex;
            // Prevent Tomcat from logging and re-throwing when we know we can
            // deal with it in the main thread, but log for information here.
            if (logger.isErrorEnabled()) {
                logger.error("Error starting Tomcat context. Exception: " + ex.getClass().getName() + ". Message: "
                        + ex.getMessage());
            }
        }
    }   
}

好像起作用的是第一个噢!只不过是一个接口函数声明,看不到是啥样的

public class ServletWebServerApplicationContext extends GenericWebApplicationContext implements ConfigurableWebServerApplicationContext {
    private void selfInitialize(ServletContext servletContext) throws ServletException {
        prepareWebApplicationContext(servletContext);
        registerApplicationScope(servletContext);
        WebApplicationContextUtils.registerEnvironmentBeans(getBeanFactory(), servletContext);
        for (ServletContextInitializer beans : getServletContextInitializerBeans()) {
            beans.onStartup(servletContext);
        }
    }
    protected Collection<ServletContextInitializer> getServletContextInitializerBeans() {
        return new ServletContextInitializerBeans(getBeanFactory());
    }
}

调用关系图

public class ServletContextInitializerBeans extends AbstractCollection<ServletContextInitializer> {
     @SafeVarargs
    @SuppressWarnings("varargs")
    public ServletContextInitializerBeans(ListableBeanFactory beanFactory,
            Class<? extends ServletContextInitializer>... initializerTypes) {
        this.initializers = new LinkedMultiValueMap<>();
        this.initializerTypes = (initializerTypes.length != 0) ? Arrays.asList(initializerTypes)
                : Collections.singletonList(ServletContextInitializer.class);
        //1添加初始化Bean
        addServletContextInitializerBeans(beanFactory);
        //2添加适配Bean
        addAdaptableBeans(beanFactory);
        //3排序
        List<ServletContextInitializer> sortedInitializers = this.initializers.values().stream()
                .flatMap((value) -> value.stream().sorted(AnnotationAwareOrderComparator.INSTANCE))
                .collect(Collectors.toList());
        this.sortedList = Collections.unmodifiableList(sortedInitializers);
        logMappings(this.initializers);
    }   
    //1添加初始化Bean
    private void addServletContextInitializerBeans(ListableBeanFactory beanFactory) {
        for (Class<? extends ServletContextInitializer> initializerType : this.initializerTypes) {
            for (Entry<String, ? extends ServletContextInitializer> initializerBean : getOrderedBeansOfType(beanFactory,initializerType)) {
                addServletContextInitializerBean(initializerBean.getKey(), initializerBean.getValue(), beanFactory);
            }
        }
    }
    //通用获取接口
    private <T> List<Entry<String, T>> getOrderedBeansOfType(ListableBeanFactory beanFactory, Class<T> type) {
        return getOrderedBeansOfType(beanFactory, type, Collections.emptySet());
    }
    //这里的type就是上级接口ServletContextInitializer,返回的就是我们自定的三个ServletRegistrationBean/FilterRegistrationBean/ServletListenerRegistrationBean,详见ServletContextInitializer继承图
    //至于这几个是什么时候注册好的,请看下回分解
    private <T> List<Entry<String, T>> getOrderedBeansOfType(ListableBeanFactory beanFactory, Class<T> type,
            Set<?> excludes) {
        String[] names = beanFactory.getBeanNamesForType(type, true, false);
        Map<String, T> map = new LinkedHashMap<>();
        for (String name : names) {
            if (!excludes.contains(name) && !ScopedProxyUtils.isScopedTarget(name)) {
                T bean = beanFactory.getBean(name, type);
                if (!excludes.contains(bean)) {
                    map.put(name, bean);
                }
            }
        }
        List<Entry<String, T>> beans = new ArrayList<>(map.entrySet());
        beans.sort((o1, o2) -> AnnotationAwareOrderComparator.INSTANCE.compare(o1.getValue(), o2.getValue()));
        return beans;
    }
    //2添加适配Bean
    protected void addAdaptableBeans(ListableBeanFactory beanFactory) {
        MultipartConfigElement multipartConfig = getMultipartConfig(beanFactory);
        addAsRegistrationBean(beanFactory, Servlet.class, new ServletRegistrationBeanAdapter(multipartConfig));
        addAsRegistrationBean(beanFactory, Filter.class, new FilterRegistrationBeanAdapter());
        for (Class<?> listenerType : ServletListenerRegistrationBean.getSupportedTypes()) {//6种监听器,见下图
            addAsRegistrationBean(beanFactory, EventListener.class, (Class<EventListener>) listenerType,
                    new ServletListenerRegistrationBeanAdapter());
        }
    }
}

大致就在这里了,没有细看,缺的没有看这几个Bean是怎么注册到Spring中
接下来走到

public class ServletWebServerApplicationContext extends GenericWebApplicationContext implements ConfigurableWebServerApplicationContext {
        private void selfInitialize(ServletContext servletContext) throws ServletException {
        prepareWebApplicationContext(servletContext);
        registerApplicationScope(servletContext);
        WebApplicationContextUtils.registerEnvironmentBeans(getBeanFactory(), servletContext);
        //这一步走完了,得到了啥 见下图
        for (ServletContextInitializer beans : getServletContextInitializerBeans()) {
            //现在到这里了
            beans.onStartup(servletContext);
        }
    }    
}

都是熟悉的面孔
上面这些组件startUp顺序执行,逻辑都差不多

其实是ServletRegistrationBean
public abstract class RegistrationBean implements ServletContextInitializer, Ordered {
    @Override
    public final void onStartup(ServletContext servletContext) throws ServletException {
        String description = getDescription();
        if (!isEnabled()) {
            logger.info(StringUtils.capitalize(description) + " was not registered (disabled)");
            return;
        }
        register(description, servletContext);
    }    
    @Override
    protected final void register(String description, ServletContext servletContext) {
        D registration = addRegistration(description, servletContext);
        if (registration == null) {
            logger.info(StringUtils.capitalize(description) + " was not registered (possibly already registered?)");
            return;
        }
        configure(registration);
    }
    @Override
    protected ServletRegistration.Dynamic addRegistration(String description, ServletContext servletContext) {
        String name = getServletName();
        return servletContext.addServlet(name, this.servlet);
    }
    @Override
    protected void configure(ServletRegistration.Dynamic registration) {
        super.configure(registration);
        String[] urlMapping = StringUtils.toStringArray(this.urlMappings);
        if (urlMapping.length == 0 && this.alwaysMapUrl) {
            urlMapping = DEFAULT_MAPPINGS;
        }
        if (!ObjectUtils.isEmpty(urlMapping)) {
            registration.addMapping(urlMapping);
        }
        registration.setLoadOnStartup(this.loadOnStartup);
        if (this.multipartConfig != null) {
            registration.setMultipartConfig(this.multipartConfig);
        }
    }
}

然后就完毕了

java

19.注册原生Servlet组件

如何注册

1.注解+启动类扫描

2.注册ServletRegistrationBean

源码