Springboot内置tomcat原理

• springmvc注解版
• 结合内置的tomcat

springmvc注解版

打开官网关于springmvc, 已经给了两种方式。链接: Springmvc

第一种

public class MyWebApplicationInitializer implements WebApplicationInitializer {

@Override
public void onStartup(ServletContext servletCxt) {

    // Load Spring web application configuration
    AnnotationConfigWebApplicationContext ac = new AnnotationConfigWebApplicationContext();
    ac.register(AppConfig.class);
    ac.refresh();

    // Create and register the DispatcherServlet
    DispatcherServlet servlet = new DispatcherServlet(ac);
    ServletRegistration.Dynamic registration = servletCxt.addServlet("app", servlet);
    registration.setLoadOnStartup(1);
    registration.addMapping("/app/*");
}
           

}

第二种

public class MyWebAppInitializer extends AbstractAnnotationConfigDispatcherServletInitializer {

@Override
protected Class<?>[] getRootConfigClasses() {
    return new Class<?>[] { RootConfig.class };
}

@Override
protected Class<?>[] getServletConfigClasses() {
    return new Class<?>[] { App1Config.class };
}

@Override
protected String[] getServletMappings() {
    return new String[] { "/app1/*" };
}
           

}

对应的xml配置

<listener>
    <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>

<context-param>
    <param-name>contextConfigLocation</param-name>
    <param-value>/WEB-INF/app-context.xml</param-value>
</context-param>

<servlet>
    <servlet-name>app</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <init-param>
        <param-name>contextConfigLocation</param-name>
        <param-value></param-value>
    </init-param>
    <load-on-startup>1</load-on-startup>
</servlet>

<servlet-mapping>
    <servlet-name>app</servlet-name>
    <url-pattern>/app/*</url-pattern>
</servlet-mapping>
           

原理：

ServletContainerInitializer是servlet3.0规范中引入的接口，能够让web应用程序在servlet容器启动后做一些自定义的操作。

ServletContainerInitializer 基于服务提供者接口（SPI）概念，因此你需要在你的jar包目录下添加META-INF/services/javax.servlet.ServletContainerInitializer文件，内容就是ServletContainerInitializer实现类的全限定名。

结合内置的tomcat

public class App {

public static void main(String[] args) {

Tomcat tomcat = new Tomcat();

tomcat.setPort(9999);

Connector conn = tomcat.getConnector(); // Tomcat 9.0 必须调用 Tomcat#getConnector() 方法之后才会监听端口

System.out.println("连接器设置完成: " + conn);

try {
        tomcat.addWebapp("/", "D:\\boot");
        tomcat.start();
        tomcat.getServer().await();
    } catch (LifecycleException e) {
        e.printStackTrace();
    }
}
           

}

tomcat作为servlet规范的实现者，默认会扫描classpath包下ServletContainerInitializer的类，作为入口，从而实现内置。

具体代码目录：https://github.com/peter-anything/springmvc

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