注册 Servlet Filter、Listener
当使用嵌入式的Servlet容器（Tomcat、Jetty等）时，我们通过将Servlet、Filter和Listener声明为Spring Bean而达到注册的效果；或者注册ServletRegistrationBean、FilterRegistrationBean 和 ServletListenerRegistrationBean的Bean。Spring Boot默认内嵌的Tomcat为servlet容器。通用的Servlet容器配置都以“server”作为前缀，而Tomcat特有配置都以“server.tomcat”作为前缀。
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。
问题
如何定制和修改Servlet容器中的相关配置；
SpringBoot能不能支持其他的Servlet容器；
配置Servler容器
配置文件
#默认程序端口为8080
server.port=8080
#用户会话session过期事件,以秒为单位
server.session.cookie.comment=60
#配配置默认的访问路径,默认为/
server.context-path= / 通常的Servlet容器设置为为server.xxx=XXX 而Tomcat的设置则为server.tomcat=XXX
源码
@ConfigurationProperties(prefix = "server", ignoreUnknownFields = true)
public class ServerProperties
implements EmbeddedServletContainerCustomizer, EnvironmentAware, Ordered {
private Integer port;
private InetAddress address;
private String contextPath;
private String displayName = "application";
@NestedConfigurationProperty
private ErrorProperties error = new ErrorProperties();
private String servletPath = "/";
private final Map<String, String> contextParameters = new HashMap<String, String>();
private Boolean useForwardHeaders;
private String serverHeader;
private int maxHttpHeaderSize = 0; // bytes
private int maxHttpPostSize = 0; // bytes
private Integer connectionTimeout;
private Session session = new Session();
@NestedConfigurationProperty
private Ssl ssl;
@NestedConfigurationProperty
private Compression compression = new Compression();
@NestedConfigurationProperty
private JspServlet jspServlet;
private final Tomcat tomcat = new Tomcat();
private final Jetty jetty = new Jetty();
private final Undertow undertow = new Undertow();
private Environment environment;代码配置
//配置嵌入式的Servlet容器
@Bean
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);
}
};
}启动服务
这个两个配置本质上都是差不多的都调用了 embeddedServletContainerCustomizer() 方法在SpringBoot中我们也会遇到很多的xxCustomizer帮助我们进行定制配置。
注册三大组件
package com.hph.springboot.config;
import com.hph.springboot.filter.MyFilter;
import com.hph.springboot.listener.MyListener;
import com.hph.springboot.servlet.MyServlet;
import org.springframework.boot.context.embedded.ConfigurableEmbeddedServletContainer;
import org.springframework.boot.context.embedded.EmbeddedServletContainerCustomizer;
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.boot.web.servlet.ServletListenerRegistrationBean;
import org.springframework.boot.web.servlet.ServletRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import java.util.Arrays;
@Configuration
public class MyServerConfig {
//注册三大组件
@Bean
public ServletRegistrationBean myServlet(){
ServletRegistrationBean registrationBean = new ServletRegistrationBean(new MyServlet(),"/myServlet");
registrationBean.setLoadOnStartup(1);
return registrationBean;
}
@Bean
public FilterRegistrationBean myFilter(){
FilterRegistrationBean registrationBean = new FilterRegistrationBean();
registrationBean.setFilter(new MyFilter());
registrationBean.setUrlPatterns(Arrays.asList("/hello","/myServlet"));
return registrationBean;
}
@Bean
public ServletListenerRegistrationBean myListener(){
ServletListenerRegistrationBean<MyListener> registrationBean = new ServletListenerRegistrationBean<>(new MyListener());
return registrationBean;
}
//配置嵌入式的Servlet容器
@Bean
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);
}
};
}
}点击ServletRegistrationBean进入
//这里的Servlet就是标准的Javax中的Servlet
public ServletRegistrationBean(Servlet servlet, String... urlMappings) {
this(servlet, true, urlMappings);
}
/**
* Create a new {@link ServletRegistrationBean} instance with the specified
* {@link Servlet} and URL mappings.
* @param servlet the servlet being mapped
* @param alwaysMapUrl if omitted URL mappings should be replaced with '/*'
* @param urlMappings the URLs being mapped
*/
public ServletRegistrationBean(Servlet servlet, boolean alwaysMapUrl,
String... urlMappings) {
Assert.notNull(servlet, "Servlet must not be null");
Assert.notNull(urlMappings, "UrlMappings must not be null");
this.servlet = servlet;
this.alwaysMapUrl = alwaysMapUrl;
this.urlMappings.addAll(Arrays.asList(urlMappings));
}
点击FilterRegistrationBean进入
public FilterRegistrationBean() {
}
/**
* Create a new {@link FilterRegistrationBean} instance to be registered with the
* specified {@link ServletRegistrationBean}s.
* @param filter the filter to register
* @param servletRegistrationBeans associate {@link ServletRegistrationBean}s
*/
public FilterRegistrationBean(Filter filter,
ServletRegistrationBean... servletRegistrationBeans) {
super(servletRegistrationBeans);
Assert.notNull(filter, "Filter must not be null");
this.filter = filter;
}
package com.hph.springboot.servlet;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
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");
}
}package com.hph.springboot.listener;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
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");
}
}package com.hph.springboot.filter;
import javax.servlet.*;
import java.io.IOException;
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() {
}
}
SpringBoot帮我们自动配置SpringMVC的时候，自动注册SpringMVC的前端控制器，DispatcherServlet;
@Bean(name = DEFAULT_DISPATCHER_SERVLET_REGISTRATION_BEAN_NAME)
@ConditionalOnBean(value = DispatcherServlet.class, name = DEFAULT_DISPATCHER_SERVLET_BEAN_NAME)
public ServletRegistrationBean dispatcherServletRegistration(
DispatcherServlet dispatcherServlet) {
ServletRegistrationBean registration = new ServletRegistrationBean(
dispatcherServlet, this.serverProperties.getServletMapping());
//默认拦截了 所有请求 包括青苔资源,但是不拦截jsp请求
registration.setName(DEFAULT_DISPATCHER_SERVLET_BEAN_NAME);
registration.setLoadOnStartup(
this.webMvcProperties.getServlet().getLoadOnStartup());
if (this.multipartConfig != null) {
registration.setMultipartConfig(this.multipartConfig);
}
return registration;
}
替换为其他的嵌入式Servlet容器
SpringBoot默认支持
Tomcat(默认使用)
<!-- 引入web模块 -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>引入web模块时默认的时Tomcat
Jetty
只需要修改pom文件即可
Undertow
原理
EmbeddedServletContainerAutoConfiguration:嵌入式的Servlet容器自动配置。
@AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE)
@Configuration
@ConditionalOnWebApplication
@Import(BeanPostProcessorsRegistrar.class)
//导入BeanPostProcessorsRegistrar：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();
}
}
- EmbeddedServletContainerFactory(嵌入式Servlet容器工厂)
public interface EmbeddedServletContainerFactory {
EmbeddedServletContainer getEmbeddedServletContainer(
ServletContextInitializer... initializers);
}- EmbeddedServletContainer：（嵌入式的Servlet容器）
在
public static class EmbeddedTomcat {
@Bean
public TomcatEmbeddedServletContainerFactory tomcatEmbeddedServletContainerFactory() {
return new TomcatEmbeddedServletContainerFactory();
}
}
//如果是 Jetty被使用 配置文件
@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();
}
}
//如果是undertow配置文件
@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();
}
}以TomcatEmbeddedServletContainerFactory为例分析
@Override
public EmbeddedServletContainer getEmbeddedServletContainer(
ServletContextInitializer... initializers) {
//创建一个Tomcat
Tomcat tomcat = new Tomcat();
//配置Tomcat的基本环节
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);
//将配置好的Tomcat传入进去，返回一个EmbeddedServletContainer；并且启动Tomcat服务器
return getTomcatEmbeddedServletContainer(tomcat);
}protected TomcatEmbeddedServletContainer getTomcatEmbeddedServletContainer(
Tomcat tomcat) {
return new TomcatEmbeddedServletContainer(tomcat, getPort() >= 0);
}public TomcatEmbeddedServletContainer(Tomcat tomcat, boolean autoStart) {
Assert.notNull(tomcat, "Tomcat Server must not be null");
this.tomcat = tomcat;
this.autoStart = autoStart;
initialize();
}
private void initialize() throws EmbeddedServletContainerException {
TomcatEmbeddedServletContainer.logger
.info("Tomcat initialized with port(s): " + getPortsDescription(false));
synchronized (this.monitor) {
try {
addInstanceIdToEngineName();
try {
// Remove service connectors to that protocol binding doesn't happen
// yet
removeServiceConnectors();
// Start the server to trigger initialization listeners
this.tomcat.start();
// We can re-throw failure exception directly in the main thread
rethrowDeferredStartupExceptions();
Context context = findContext();
try {
ContextBindings.bindClassLoader(context, getNamingToken(context),
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) {
containerCounter.decrementAndGet();
throw ex;
}
}
catch (Exception ex) {
throw new EmbeddedServletContainerException(
"Unable to start embedded Tomcat", ex);
}
}
}如何对嵌入式容器的配置修改时怎么样生效的。
- 使用serverProperties
- EmbeddedServletContainerCustomizer : 定制器帮我们修改了Servlet容器的配置导入BeanPostProcessorsRegistrar：给容器中导入一些组件
@Override
public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata,
BeanDefinitionRegistry registry) {
if (this.beanFactory == null) {
return;
}
registerSyntheticBeanIfMissing(registry,
"embeddedServletContainerCustomizerBeanPostProcessor",
EmbeddedServletContainerCustomizerBeanPostProcessor.class);
registerSyntheticBeanIfMissing(registry,
"errorPageRegistrarBeanPostProcessor",
ErrorPageRegistrarBeanPostProcessor.class);
}
容器中导入了EmbeddedServletContainerCustomizerBeanPostProcessor
//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也是定制器步骤
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
嵌入式Servlet容器启动原理
什么时候创建嵌入式的Servlet容器工厂？什么时候获取嵌入式的Servlet容器并启动Tomcat；
获取嵌入式的Servlet容器工厂：
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；
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）、 onRefresh(); web的ioc容器重写了onRefresh方法
5）、webioc容器会创建嵌入式的Servlet容器；createEmbeddedServletContainer();
6）、获取嵌入式的Servlet容器工厂：
EmbeddedServletContainerFactory containerFactory = getEmbeddedServletContainerFactory();
从ioc容器中获取EmbeddedServletContainerFactory 组件；TomcatEmbeddedServletContainerFactory创建对象，后置处理器一看是这个对象，就获取所有的定制器来先定制Servlet容器的相关配置；
7）、使用容器工厂获取嵌入式的Servlet容器：this.embeddedServletContainer = containerFactory .getEmbeddedServletContainer(getSelfInitializer());
8）、嵌入式的Servlet容器创建对象并启动Servlet容器；
先启动嵌入式的Servlet容器，再将ioc容器中剩下没有创建出的对象获取出来；
IOC容器启动创建嵌入式的Servlet容器
