关于java:springboot源码解析管中窥豹系列之web服务器七

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一、前言

  • Springboot 源码解析是一件大工程，逐行逐句的去钻研代码，会很干燥，也不容易坚持下去。
  • 咱们不谋求大而全，而是试着每次去钻研一个小知识点，最终聚沙成塔，这就是咱们的 springboot 源码管中窥豹系列。

二、web 服务器

  • 以前的的 spring 我的项目或者 springmvc 我的项目都须要一个 web 服务器，tomcat, 或者其它的
  • 应用 springboot 之后，咱们不再须要配置 web 服务器，因为 springboot 帮咱们集成了
  • 明天咱们来剖析一下源码，看看在哪里实现的，知其然知其所以然

三、源码剖析

  • 还是从 SpringApplication 的 run 办法开始看
  • 不相熟的能够看之前的文章：springboot 源码解析 - 管中窥豹系列之总体构造（一）
SpringApplication.java
public ConfigurableApplicationContext run(String... args) {
 
    ...

    try {
        
        ...

        refreshContext(context);
        
        ...

    }
    catch (Throwable ex) {...}

    ...

    return context;
}
  • 接着进入到 refreshContext(context) 外面 
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 {...}
    }
}
  • 进入到 onRefresh() 办法 
protected void onRefresh() throws BeansException {// For subclasses: do nothing by default.}
  • 留神这个是一个 protected 办法，咱们进入到子实现外面
  • 具体用的哪个 context，请看之前的文章：springboot 源码解析 - 管中窥豹系列之我的项目类型（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);
}
  • 最罕用的就是一般 web 我的项目，咱们看这一个
  • 咱们到 org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext 外面找 onRefresh() 办法
  • 没找到，在父类 ServletWebServerApplicationContext 外面找到了 
ServletWebServerApplicationContext.java

@Override
protected void onRefresh() {super.onRefresh();
    try {createWebServer();
    }
    catch (Throwable ex) {throw new ApplicationContextException("Unable to start web server", ex);
    }
}
  • 咱们到 createWebServer() 办法外面 
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();}
  • 用的工厂模式，先找到工厂 getWebServerFactory()
  • 再用工厂生成 webServer, factory.getWebServer(getSelfInitializer())
  • 先看看 getWebServerFactory() 这个办法 
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);
}
  • 获取惟一的工厂：ServletWebServerFactory，多了少了都不行
  • 在哪加载进 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 外面是蕴含了 spring-boot-starter 依赖的
  • spring-boot-starter 外面蕴含了 spring-boot-autoconfigure 依赖
  • spring-boot-autoconfigure 外面有一个类：ServletWebServerFactoryConfiguration
  • 这个类外面有一个动态类: 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 : 它依赖 Servlet.class, Tomcat.class, UpgradeProtocol.class
  • ConditionalOnMissingBean：避免反复加载
  • 至此，factory 怎么加载进 spring 就找到了
  • 咱们多看一点，这个类 ServletWebServerFactoryConfiguration 还有两个动态类 
@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;
    }

}
  • 一个是生成 jetty 服务器工厂，一个是生成 undertow 服务器工厂
  • 它们的加载，取决于依赖的 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

如果咱们想换成 undertow 服务器，依赖改了就行了 

<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>

如果咱们想换成 jetty 服务器，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>
  • 思维拉回来，工厂有了，咱们看看工厂怎么生成的 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);
}
  • 这个办法咱们就不剖析了，就是生成 tomcat 服务器，和 spring 关联不大，改天咱们专门剖析 tomcat 源码
  • 至此，整个 springboot 的加载 web 服务器过程就完了

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正文完
java
发表至： java
2021-02-04
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