一、前言
- Springboot原始碼解析是一件大工程，逐行逐句的去研究程式碼，會很枯燥，也不容易堅持下去。
- 我們不追求大而全，而是試著每次去研究一個小知識點，最終聚沙成塔，這就是我們的springboot原始碼管中窺豹系列。
二、web伺服器
- 以前的的spring專案或者springmvc專案都需要一個web伺服器，tomcat,或者其它的
- 使用springboot之後，我們不再需要配置web伺服器，因為springboot幫我們整合了
- 今天我們來分析一下原始碼，看看在哪裡實現的，知其然知其所以然
三、原始碼分析
- 還是從SpringApplication的run方法開始看
- 不熟悉的可以看之前的文章：springboot原始碼解析-管中窺豹系列之總體結構（一）
SpringApplication.java
public ConfigurableApplicationContext run(String... args) {
...
try {
...
refreshContext(context);
...
}
catch (Throwable ex) {
...
}
...
return context;
}
- 接著進入到 refreshContext(context) 裡面
AbstractApplicationContext.java
@Override
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
...
try {
...
// Initialize other special beans in specific context subclasses.
onRefresh();
...
}
catch (BeansException ex) {
...
}
finally {
...
}
}
}
- 進入到 onRefresh() 方法
protected void onRefresh() throws BeansException {
// For subclasses: do nothing by default.
}
- 注意這個是一個protected方法，我們進入到子實現裡面
- 具體用的哪個context，請看之前的文章：springboot原始碼解析-管中窺豹系列之專案型別（二）
public static final String DEFAULT_CONTEXT_CLASS = "org.springframework.context."
+ "annotation.AnnotationConfigApplicationContext";
public static final String DEFAULT_SERVLET_WEB_CONTEXT_CLASS = "org.springframework.boot."
+ "web.servlet.context.AnnotationConfigServletWebServerApplicationContext";
public static final String DEFAULT_REACTIVE_WEB_CONTEXT_CLASS = "org.springframework."
+ "boot.web.reactive.context.AnnotationConfigReactiveWebServerApplicationContext";
protected ConfigurableApplicationContext createApplicationContext() {
Class<?> contextClass = this.applicationContextClass;
if (contextClass == null) {
try {
switch (this.webApplicationType) {
case SERVLET:
contextClass = Class.forName(DEFAULT_SERVLET_WEB_CONTEXT_CLASS);
break;
case REACTIVE:
contextClass = Class.forName(DEFAULT_REACTIVE_WEB_CONTEXT_CLASS);
break;
default:
contextClass = Class.forName(DEFAULT_CONTEXT_CLASS);
}
}
catch (ClassNotFoundException ex) {
throw new IllegalStateException(
"Unable create a default ApplicationContext, please specify an ApplicationContextClass", ex);
}
}
return (ConfigurableApplicationContext) BeanUtils.instantiateClass(contextClass);
}
- 最常用的就是普通web專案，我們看這一個
- 我們到org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext裡面找 onRefresh() 方法
- 沒找到，在父類ServletWebServerApplicationContext裡面找到了
ServletWebServerApplicationContext.java
@Override
protected void onRefresh() {
super.onRefresh();
try {
createWebServer();
}
catch (Throwable ex) {
throw new ApplicationContextException("Unable to start web server", ex);
}
}
- 我們到 createWebServer() 方法裡面
private void createWebServer() {
WebServer webServer = this.webServer;
ServletContext servletContext = getServletContext();
if (webServer == null && servletContext == null) {
ServletWebServerFactory factory = getWebServerFactory();
this.webServer = factory.getWebServer(getSelfInitializer());
}
else if (servletContext != null) {
try {
getSelfInitializer().onStartup(servletContext);
}
catch (ServletException ex) {
throw new ApplicationContextException("Cannot initialize servlet context",
ex);
}
}
initPropertySources();
}
- 用的工廠模式，先找到工廠getWebServerFactory()
- 再用工廠生成webServer, factory.getWebServer(getSelfInitializer())
- 先看看 getWebServerFactory() 這個方法
protected ServletWebServerFactory getWebServerFactory() {
// Use bean names so that we don't consider the hierarchy
String[] beanNames = getBeanFactory()
.getBeanNamesForType(ServletWebServerFactory.class);
if (beanNames.length == 0) {
throw new ApplicationContextException(
"Unable to start ServletWebServerApplicationContext due to missing "
+ "ServletWebServerFactory bean.");
}
if (beanNames.length > 1) {
throw new ApplicationContextException(
"Unable to start ServletWebServerApplicationContext due to multiple "
+ "ServletWebServerFactory beans : "
+ StringUtils.arrayToCommaDelimitedString(beanNames));
}
return getBeanFactory().getBean(beanNames[0], ServletWebServerFactory.class);
}
- 獲取唯一的工廠：ServletWebServerFactory，多了少了都不行
- 在哪載入進springboot的呢？
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter</artifactId>
<scope>compile</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-autoconfigure</artifactId>
<scope>compile</scope>
</dependency>
- spring-boot-starter-web裡面是包含了spring-boot-starter依賴的
- spring-boot-starter裡面包含了spring-boot-autoconfigure依賴
- spring-boot-autoconfigure裡面有一個類：ServletWebServerFactoryConfiguration
- 這個類裡面有一個靜態類: EmbeddedTomcat
@Configuration(proxyBeanMethods = false)
@ConditionalOnClass({ Servlet.class, Tomcat.class, UpgradeProtocol.class })
@ConditionalOnMissingBean(value = ServletWebServerFactory.class, search = SearchStrategy.CURRENT)
static class EmbeddedTomcat {
@Bean
TomcatServletWebServerFactory tomcatServletWebServerFactory(
ObjectProvider<TomcatConnectorCustomizer> connectorCustomizers,
ObjectProvider<TomcatContextCustomizer> contextCustomizers,
ObjectProvider<TomcatProtocolHandlerCustomizer<?>> protocolHandlerCustomizers) {
TomcatServletWebServerFactory factory = new TomcatServletWebServerFactory();
factory.getTomcatConnectorCustomizers()
.addAll(connectorCustomizers.orderedStream().collect(Collectors.toList()));
factory.getTomcatContextCustomizers()
.addAll(contextCustomizers.orderedStream().collect(Collectors.toList()));
factory.getTomcatProtocolHandlerCustomizers()
.addAll(protocolHandlerCustomizers.orderedStream().collect(Collectors.toList()));
return factory;
}
}
- ConditionOnClass : 它依賴 Servlet.class, Tomcat.class, UpgradeProtocol.class
- ConditionalOnMissingBean： 防止重複載入
- 至此，factory怎麼載入進spring就找到了
- 我們多看一點，這個類ServletWebServerFactoryConfiguration還有兩個靜態類
@Configuration(proxyBeanMethods = false)
@ConditionalOnClass({ Servlet.class, Server.class, Loader.class, WebAppContext.class })
@ConditionalOnMissingBean(value = ServletWebServerFactory.class, search = SearchStrategy.CURRENT)
static class EmbeddedJetty {
@Bean
JettyServletWebServerFactory JettyServletWebServerFactory(
ObjectProvider<JettyServerCustomizer> serverCustomizers) {
JettyServletWebServerFactory factory = new JettyServletWebServerFactory();
factory.getServerCustomizers().addAll(serverCustomizers.orderedStream().collect(Collectors.toList()));
return factory;
}
}
@Configuration(proxyBeanMethods = false)
@ConditionalOnClass({ Servlet.class, Undertow.class, SslClientAuthMode.class })
@ConditionalOnMissingBean(value = ServletWebServerFactory.class, search = SearchStrategy.CURRENT)
static class EmbeddedUndertow {
@Bean
UndertowServletWebServerFactory undertowServletWebServerFactory(
ObjectProvider<UndertowDeploymentInfoCustomizer> deploymentInfoCustomizers,
ObjectProvider<UndertowBuilderCustomizer> builderCustomizers) {
UndertowServletWebServerFactory factory = new UndertowServletWebServerFactory();
factory.getDeploymentInfoCustomizers()
.addAll(deploymentInfoCustomizers.orderedStream().collect(Collectors.toList()));
factory.getBuilderCustomizers().addAll(builderCustomizers.orderedStream().collect(Collectors.toList()));
return factory;
}
}
- 一個是生成jetty伺服器工廠，一個是生成undertow伺服器工廠
- 它們的載入，取決於依賴的class是否存在
- tomcat: Servlet.class, Tomcat.class, UpgradeProtocol.class
- jetty: Servlet.class, Server.class, Loader.class, WebAppContext.class
- undertow: Servlet.class, Undertow.class, SslClientAuthMode.class
假如我們想換成undertow伺服器，依賴改了就行了
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
<exclusions>
<exclusion>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-tomcat</artifactId>
</exclusion>
</exclusions>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-undertow</artifactId>
</dependency>
假如我們想換成jetty伺服器，同理
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
<exclusions>
<exclusion>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-tomcat</artifactId>
</exclusion>
</exclusions>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-jetty</artifactId>
</dependency>
- 思維拉回來，工廠有了，我們看看工廠怎麼生成的webServer
TomcatServletWebServerFactory.java
@Override
public WebServer getWebServer(ServletContextInitializer... initializers) {
if (this.disableMBeanRegistry) {
Registry.disableRegistry();
}
Tomcat tomcat = new Tomcat();
File baseDir = (this.baseDirectory != null) ? this.baseDirectory : createTempDir("tomcat");
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);
return getTomcatWebServer(tomcat);
}
- 這個方法我們就不分析了，就是生成tomcat伺服器，和spring關聯不大，改天我們專門分析tomcat原始碼
- 至此，整個springboot的載入web伺服器過程就完了
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