SpringBoot配置嵌入式的Servlet
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SpringBoot默认使用Tomcat作为嵌入式的Servlet
问题？
server.port=8081 server.context-path=/crud server.tomcat.uri-encoding=UTF-8 //通用的Servlet容器设置 server.xxx //Tomcat的设置 server.tomcat.xxx
注：在2.0之前的版本当中可以使用以下方式修改 Servlet （EmbeddedServletContainerCustomizer 为 ServerProperties 父类）
@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(8083);
}
};
}
由于SpringBoot默认是以jar包的方式启动嵌入式的Servlet容器来启动SpringBoot的web应用，没有web.xml文件。
注册三大组件用以下方式
@Bean
public ServletRegistrationBean myServlet(){
ServletRegistrationBean registrationBean = new ServletRegistrationBean(new MyServlet(),"/myServlet");
return registrationBean;
}
public class MyServlet extends HttpServlet {
//处理get请求
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doPost(req,resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
resp.getWriter().write("Hello MyServlet");
}
}
FilterRegistrationBean
@Bean
public FilterRegistrationBean myFilter(){
FilterRegistrationBean registrationBean = new FilterRegistrationBean();
registrationBean.setFilter(new MyFilter());
registrationBean.setUrlPatterns(Arrays.asList("/hello","/myServlet"));
return registrationBean;
}
public class MyFilter implements Filter {
@Override
public void init(FilterConfig filterConfig) throws ServletException {
}
@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
System.out.println("MyFilter process...");
chain.doFilter(request,response);
}
@Override
public void destroy() {
}
}
ServletListenerRegistrationBean
@Bean
public ServletListenerRegistrationBean myListener(){
ServletListenerRegistrationBean<MyListener> registrationBean = new ServletListenerRegistrationBean<>(new MyListener());
return registrationBean;
}
public class MyListener implements ServletContextListener {
@Override
public void contextInitialized(ServletContextEvent sce) {
System.out.println("contextInitialized...web应用启动");
}
@Override
public void contextDestroyed(ServletContextEvent sce) {
System.out.println("contextDestroyed...当前web项目销毁");
}
}
这种注册方式最好的例子（注册 DIspatcherServlet ）
SpringBoot帮我们自动SpringMVC的时候，自动的注册SpringMVC的前端控制器；DIspatcherServlet；
@Bean(
name = {"dispatcherServletRegistration"}
)
@ConditionalOnBean(
value = {DispatcherServlet.class},
name = {"dispatcherServlet"}
)
public DispatcherServletRegistrationBean dispatcherServletRegistration(DispatcherServlet dispatcherServlet, WebMvcProperties webMvcProperties, ObjectProvider<MultipartConfigElement> multipartConfig) {
//默认拦截： / 所有请求；包静态资源，但是不拦截jsp请求； /*会拦截jsp
//可以通过 spring.mvc.servlet.path (之前版本是server.servletPath) 来修改SpringMVC前端控制器默认拦截的请求路径
DispatcherServletRegistrationBean registration = new DispatcherServletRegistrationBean(dispatcherServlet, webMvcProperties.getServlet().getPath());
registration.setName("dispatcherServlet");
registration.setLoadOnStartup(webMvcProperties.getServlet().getLoadOnStartup());
multipartConfig.ifAvailable(registration::setMultipartConfig);
return registration;
}
2）、SpringBoot能不能支持其他的Servlet容器；
Spring Boot 的 web 项目默认使用嵌入式的 Tomcat 服务器，同时它也支持程序员自己切换 内置的 Servlet 容器，如 Jetty 、Undertow
Jetty 支持长连接，对于页面与服务器类似建立长连接聊天式的性能很好，
Undertow 高性能非阻塞的，并发性能非常好，但是不支持JSP
②
Tomcat 与 Undertow 对比
1、Tomcat
是 Apache 基金下的一个轻量级的 Servlet 容器，支持 Servlet 和 JSP。Tomcat 具有 Web
服务器特有的功能，包括 Tomcat 管理和控制平台、安全局管理和 Tomcat 阀等。Tomcat 本身包含了 HTTP
服务器，因此也可以视作单独的 Web 服务器。
2、但是，Tomcat 和 ApacheHTTP 服务器不是同一个东西，ApacheHTTP 服务器是用 C 语言实现的 HTTP Web 服务器。Tomcat 是完全免费的，深受开发者的喜爱。
3、Undertow
是 Red Hat 公司的开源产品, 它完全采用 Java 语言开发，是一款灵活的高性能 Web 服务器，支持阻塞 IO 和非阻塞 IO。由于
Undertow 采用 Java 语言开发，可以直接嵌入到 Java 项目中使用。同时，Undertow 完全支持 Servlet 和 Web
Socket，在高并发情况下表现非常出色。
@Configuration(
proxyBeanMethods = false
)
@ConditionalOnWebApplication
@EnableConfigurationProperties({ServerProperties.class})
public class EmbeddedWebServerFactoryCustomizerAutoConfiguration {
public EmbeddedWebServerFactoryCustomizerAutoConfiguration() {
默认支持：
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
引入web模块默认就是使用嵌入式的Tomcat作为Servlet容器；
Jetty
<!-- 引入web模块 -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
<exclusions>
<exclusion>
<artifactId>spring-boot-starter-tomcat</artifactId>
<groupId>org.springframework.boot</groupId>
</exclusion>
</exclusions>
</dependency>
<!--引入其他的Servlet容器-->
<dependency>
<artifactId>spring-boot-starter-jetty</artifactId>
<groupId>org.springframework.boot</groupId>
</dependency>
Undertow
<!-- 引入web模块 -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
<exclusions>
<exclusion>
<artifactId>spring-boot-starter-tomcat</artifactId>
<groupId>org.springframework.boot</groupId>
</exclusion>
</exclusions>
</dependency>
<!--引入其他的Servlet容器-->
<dependency>
<artifactId>spring-boot-starter-undertow</artifactId>
<groupId>org.springframework.boot</groupId>
</dependency>
@AutoConfigureOrder(-2147483648)
@ConditionalOnClass({ServletRequest.class})
@ConditionalOnWebApplication(
type = Type.SERVLET
)
//启动自动配置
@EnableConfigurationProperties({ServerProperties.class})
//根据条件给容器中导入嵌入式的容器
@Import({ServletWebServerFactoryAutoConfiguration.BeanPostProcessorsRegistrar.class, EmbeddedTomcat.class, EmbeddedJetty.class, EmbeddedUndertow.class})
public class ServletWebServerFactoryAutoConfiguration {
public ServletWebServerFactoryAutoConfiguration() {
}
@Bean
public ServletWebServerFactoryCustomizer servletWebServerFactoryCustomizer(ServerProperties serverProperties) {
return new ServletWebServerFactoryCustomizer(serverProperties);
}
以导入Tomcat为例，查看Tomcat依赖组件，如果满足则导入tomcat工厂，以此获取Tomcat容器
通过Tomcat工厂获取tomcat容器的代码如下
@Override
public WebServer getWebServer(ServletContextInitializer... initializers) {
if (this.disableMBeanRegistry) {
Registry.disableRegistry();
}
//创建一个Tomcat
Tomcat tomcat = new Tomcat();
File baseDir = (this.baseDirectory != null) ? this.baseDirectory : createTempDir("tomcat");
//配置Tomcat的基本环节
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);
//将配置好的Tomcat传入进去，返回一个 TomcatWebServer ；并且启动Tomcat服务器
return getTomcatWebServer(tomcat);
}
启动tomcat的整个调用链路如下
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(); } private void initialize() throws WebServerException { 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(); destroySilently(); throw new WebServerException("Unable to start embedded Tomcat", ex); } } }
2.0之后的启动步骤
配置文件初始化----》容器工厂的初始化
2.x之前的方式
@AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE)
@Configuration
@ConditionalOnWebApplication
@Import(BeanPostProcessorsRegistrar.class)
//导入BeanPostProcessorsRegistrar：Spring注解版；给容器中导入一些组件
//导入了EmbeddedServletContainerCustomizerBeanPostProcessor：
//后置处理器：bean初始化前后（创建完对象，还没赋值赋值）执行初始化工作
public class EmbeddedServletContainerAutoConfiguration {
@Configuration
@ConditionalOnClass({ Servlet.class, Tomcat.class })//判断当前是否引入了Tomcat依赖；
@ConditionalOnMissingBean(value = EmbeddedServletContainerFactory.class, search = SearchStrategy.CURRENT)//判断当前容器没有用户自己定义EmbeddedServletContainerFactory：嵌入式的Servlet容器工厂；作用：创建嵌入式的Servlet容器
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();
}
}
//初始化之前
@Override
public Object postProcessBeforeInitialization(Object bean, String beanName)
throws BeansException {
//如果当前初始化的是一个ConfigurableEmbeddedServletContainer类型的组件
if (bean instanceof ConfigurableEmbeddedServletContainer) {
//
postProcessBeforeInitialization((ConfigurableEmbeddedServletContainer) bean);
}
return bean;
}
private void postProcessBeforeInitialization(
ConfigurableEmbeddedServletContainer bean) {
//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；
for (EmbeddedServletContainerCustomizer customizer : getCustomizers()) {
customizer.customize(bean);
}
}
private Collection<EmbeddedServletContainerCustomizer> getCustomizers() {
if (this.customizers == null) {
// Look up does not include the parent context
this.customizers = new ArrayList<EmbeddedServletContainerCustomizer>(
this.beanFactory
//从容器中获取所有这葛类型的组件：EmbeddedServletContainerCustomizer
//定制Servlet容器，给容器中可以添加一个EmbeddedServletContainerCustomizer类型的组件
.getBeansOfType(EmbeddedServletContainerCustomizer.class,
false, false)
.values());
Collections.sort(this.customizers, AnnotationAwareOrderComparator.INSTANCE);
this.customizers = Collections.unmodifiableList(this.customizers);
}
return this.customizers;
}
ServerProperties也是定制器
2.x之前的初始化步骤：
1）、SpringBoot根据导入的依赖情况，给容器中添加相应的EmbeddedServletContainerFactory【TomcatEmbeddedServletContainerFactory】
2）、容器中某个组件要创建对象就会惊动后置处理器；EmbeddedServletContainerCustomizerBeanPostProcessor；
只要是嵌入式的Servlet容器工厂，后置处理器就工作；
3）、后置处理器，从容器中获取所有的EmbeddedServletContainerCustomizer，调用定制器的定制方法
备注：
springboot2.x中嵌入式servlet相关类变动说明
1.Spring Boot2.0以上版本EmbeddedServletContainerCustomizer被WebServerFactoryCustomizer替代 === https://blog.csdn.net/Hard__ball/article/details/81281898?depth_1-utm_source=distribute.pc_relevant.none-task&utm_source=distribute.pc_relevant.none-task 在Spring Boot2.0以上配置嵌入式Servlet容器时EmbeddedServletContainerCustomizer类不存在，经网络查询发现被WebServerFactoryCustomizer替代 2.EmbeddedServletContainerAutoConfiguration and ServerPropertiesAutoConfiguration in Spring Boot 2.0 ==== https://stackoverflow.com/questions/52393841/embeddedservletcontainerautoconfiguration-and-serverpropertiesautoconfiguration EmbeddedServletContainerAutoConfiguration has been renamed to ServletWebServerFactoryAutoConfiguration by this commit during work on restructuring embedded web server packages. ServerPropertiesAutoConfiguration has been removed by this commit during work on the following issue. Those properties objects are now created using @EnableConfigurationProperties only.
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