配置嵌入式Servlet容器

一、如何定制和修改Servlet容器的相关配置

　　1）修改server有关的配置(ServerProperties)

server.port=8081
server.context‐path=/crud
server.tomcat.uri‐encoding=UTF‐8

　　2）EmbeddedServletContainerCustomizer

@Bean //一定要将这个定制器加入到容器中
public EmbeddedServletContainerCustomizer embeddedServletContainerCustomizer(){
　　return new EmbeddedServletContainerCustomizer() {
　　　　//定制嵌入式的Servlet容器相关的规则
　　　　@Override
　　　　public void customize(ConfigurableEmbeddedServletContainer container) {
　　　　　　container.setPort(8081);
　　　　}
　　};
}

ServerProperties、EmbeddedServletContainerCustomizer定制器怎么就帮我们修改了Servlet容器的配置呢

容器中导入了EmbeddedServletContainerCustomizerBeanPostProcessor　

spring创建对象，填充属性之前，执行applyBeanPostProcessorsBeforeInitialization

@Override
    public Object applyBeanPostProcessorsBeforeInitialization(Object existingBean, String beanName)
            throws BeansException {

        Object result = existingBean;
        for (BeanPostProcessor processor : getBeanPostProcessors()) {
            result = processor.postProcessBeforeInitialization(result, beanName);
            if (result == null) {
                return result;
            }
        }
        return result;
    }

public class EmbeddedServletContainerCustomizerBeanPostProcessor
        implements BeanPostProcessor, BeanFactoryAware {

    private ListableBeanFactory beanFactory;

    private List<EmbeddedServletContainerCustomizer> customizers;


    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName)
            throws BeansException {
        if (bean instanceof ConfigurableEmbeddedServletContainer) {//如果当前初始化的是一个ConfigurableEmbeddedServletContainer类型的组件
            postProcessBeforeInitialization((ConfigurableEmbeddedServletContainer) bean);
        }
        return bean;
    }

private void postProcessBeforeInitialization(
            ConfigurableEmbeddedServletContainer bean) {
        for (EmbeddedServletContainerCustomizer customizer : getCustomizers()) {//获取所有的定制器，调用每一个定制器的customize方法来给Servlet容器进行属性赋值；
            customizer.customize(bean);
        }
    }

    private Collection<EmbeddedServletContainerCustomizer> getCustomizers() {
        if (this.customizers == null) {
            // Look up does not include the parent context
            this.customizers = new ArrayList<EmbeddedServletContainerCustomizer>(//从容器中获取所有这葛类型的组件：EmbeddedServletContainerCustomizer
                    this.beanFactory
                            .getBeansOfType(EmbeddedServletContainerCustomizer.class,
                                    false, false)
                            .values());
            Collections.sort(this.customizers, AnnotationAwareOrderComparator.INSTANCE);
            this.customizers = Collections.unmodifiableList(this.customizers);
        }
        return this.customizers;
    }

ServerProperties

 1 @ConfigurationProperties(prefix = "server", ignoreUnknownFields = true)
 2 public class ServerProperties
 3         implements EmbeddedServletContainerCustomizer, EnvironmentAware, Ordered {
 4 
 5 @Override
 6     public void customize(ConfigurableEmbeddedServletContainer container) {
 7         if (getPort() != null) {
 8             container.setPort(getPort());
 9         }
10         if (getAddress() != null) {
11             container.setAddress(getAddress());
12         }
13         if (getContextPath() != null) {
14             container.setContextPath(getContextPath());
15         }
16         if (getDisplayName() != null) {
17             container.setDisplayName(getDisplayName());
　　　　　　......

2）注册Servlet三大组件【Servlet、Filter、Listener】

　　ServletRegistrationBean、FilterRegistrationBean、ServletListenerRegistrationBean

　　@Bean
    public ServletRegistrationBean myServlet(){
        return new ServletRegistrationBean(new MyServlet(),"/myServlet");
    }

3）嵌入式Servlet容器自动配置原理--EmbeddedServletContainerAutoConfiguration

@AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE)
@Configuration
@ConditionalOnWebApplication
@Import(BeanPostProcessorsRegistrar.class)
public class EmbeddedServletContainerAutoConfiguration {

    /**
     * Nested configuration if Tomcat is being used.
     */
    @Configuration
    @ConditionalOnClass({ Servlet.class, Tomcat.class })
    @ConditionalOnMissingBean(value = EmbeddedServletContainerFactory.class, search = SearchStrategy.CURRENT)
    public static class EmbeddedTomcat {

        @Bean
        public TomcatEmbeddedServletContainerFactory tomcatEmbeddedServletContainerFactory() {
            return new TomcatEmbeddedServletContainerFactory();
        }

    }

    /**
     * Nested configuration if Jetty is being used.
     */
    @Configuration
    @ConditionalOnClass({ Servlet.class, Server.class, Loader.class,
            WebAppContext.class })
    @ConditionalOnMissingBean(value = EmbeddedServletContainerFactory.class, search = SearchStrategy.CURRENT)
    public static class EmbeddedJetty {

        @Bean
        public JettyEmbeddedServletContainerFactory jettyEmbeddedServletContainerFactory() {
            return new JettyEmbeddedServletContainerFactory();
        }

    }

    /**
     * Nested configuration if Undertow is being used.
     */
    @Configuration
    @ConditionalOnClass({ Servlet.class, Undertow.class, SslClientAuthMode.class })
    @ConditionalOnMissingBean(value = EmbeddedServletContainerFactory.class, search = SearchStrategy.CURRENT)
    public static class EmbeddedUndertow {

        @Bean
        public UndertowEmbeddedServletContainerFactory undertowEmbeddedServletContainerFactory() {
            return new UndertowEmbeddedServletContainerFactory();
        }

    }

 EmbeddedServletContainerFactory（嵌入式Servlet容器工厂）

 EmbeddedServletContainer：（嵌入式的Servlet容器）

以TomcatEmbeddedServletContainerFactory为例

public EmbeddedServletContainer getEmbeddedServletContainer(
            ServletContextInitializer... initializers) {
        Tomcat tomcat = new Tomcat();
        File baseDir = (this.baseDirectory != null) ? this.baseDirectory
                : createTempDir("tomcat");
        tomcat.setBaseDir(baseDir.getAbsolutePath());
        Connector connector = new Connector(this.protocol);
        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 getTomcatEmbeddedServletContainer(tomcat);//将配置好的Tomcat传入进去，返回一个EmbeddedServletContainer；并且启动Tomcat服务器
    }

4）嵌入式Servlet容器启动原理

　　1、SpringBoot应用启动运行run方法

　　2、refreshContext(context);SpringBoot刷新IOC容器【创建IOC容器对象，并初始化容器，创建容器中的每一
个组件】；如果是web应用创建AnnotationConfigEmbeddedWebApplicationContext，否则：
AnnotationConfigApplicationContext
　　3、refresh(context);刷新刚才创建好的ioc容器；

@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();
            }
        }
    }

　　4、AnnotationConfigEmbeddedWebApplicationContext重写该onRefresh()。

protected void onRefresh() {
        super.onRefresh();
        try {
            createEmbeddedServletContainer();
        }
        catch (Throwable ex) {
            throw new ApplicationContextException("Unable to start embedded container",
                    ex);
        }
    }

private void createEmbeddedServletContainer() {
        EmbeddedServletContainer localContainer = this.embeddedServletContainer;
        ServletContext localServletContext = getServletContext();
        if (localContainer == null && localServletContext == null) {
            EmbeddedServletContainerFactory containerFactory = getEmbeddedServletContainerFactory();
            this.embeddedServletContainer = containerFactory
                    .getEmbeddedServletContainer(getSelfInitializer());
        }
        else if (localServletContext != null) {
            try {
                getSelfInitializer().onStartup(localServletContext);
            }
            catch (ServletException ex) {
                throw new ApplicationContextException("Cannot initialize servlet context",
                        ex);
            }
        }
        initPropertySources();
    }