02-01:springboot整合servlet开发

1.通过注解扫描完成servlet组件的注册

　　1.1 编写servlet，在类上添加（WebServlet注解，就表示该类是一个servlet）：@WebServlet(name="FirstServlet",urlPatterns="/first")

@WebServlet(name="FirstServlet",urlPatterns="/first")
public class FirstServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("FirstServlet......");
    }
}

       1.2编写启动类：@ServletComponentScan 在springBoot启动时会扫描@webServlet,并将改类实例化

@SpringBootApplication
@ServletComponentScan
public class App {
    public static void main(String[] args) {
        SpringApplication.run(App.class, args);
    }
}

2.通过方法完成servlet组件的注册（不需要添加annotation注解）

 2.1编写servlet

public class SecondServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("SecondServlet.....");
    }
}

2.2 编写启动类

 不需要ServletComponentScan 注解类扫描；

@SpringBootApplication
public class App2 {
    public static void main(String[] args) {
        SpringApplication.run(App2.class, args);
    }
    @Bean
    public ServletRegistrationBean  getServletRegistrationBean () {
        ServletRegistrationBean bean = new ServletRegistrationBean(new SecondServlet());
        bean.addUrlMappings("/second");
        return bean;
        
    } 
}

ServletRegistrationBean 这个类来注解一个servlet；