SpringBoot中原生组件（Servlet、Filter、Listener）的使用

1、使用Servlet API

@ServletComponentScan(basePackages = "com.atguigu.admin") :指定原生Servlet组件都放在那里 
@WebServlet(urlPatterns = "/my")： 思考：直接响应，没有经过Spring的拦截器？
@WebFilter(urlPatterns={"/css/*","/images/*"})
@WebListener

示例：@WebServlet，@WebFilter和@WebListener 使用大体相似

/**
 * @ServletComponentSc 帮我们把servlet 扫描进去
 */
@ServletComponentScan(basePackages = "com.song.admin")
@SpringBootApplication
public class Boot05WebAdminApplication {

    public static void main(String[] args) {
        SpringApplication.run(Boot05WebAdminApplication.class, args);
    }

}

=============================================================================

@WebServlet(urlPatterns = "/my")
public class MyServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.getWriter().write("666666");
    }
}

2、使用RegistrationBean

方式二：ServletRegistrationBean，FilterRegistrationBean，ServletListenerRegistrationBean

package com.song.admin.registServlet;

import com.song.admin.servlet.MyFilter;
import com.song.admin.servlet.MyListener;
import com.song.admin.servlet.MyServlet;
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 MyRegistConfig {

    @Bean
    public ServletRegistrationBean myServlet(){
        MyServlet myServlet = new MyServlet();
        return new ServletRegistrationBean(myServlet,"/my");

    }


    @Bean
    public FilterRegistrationBean myFilter(){
        MyFilter myFilter = new MyFilter();

        FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean(myFilter);
        filterRegistrationBean.setUrlPatterns(Arrays.asList("/my","/css/*"));

        return filterRegistrationBean;

        //这个 就相当于于 过滤的路径 和 上面一样
//        return new FilterRegistrationBean(myFilter,myServlet());
    }

    @Bean
    public ServletListenerRegistrationBean myListener(){
        MyListener myListener = new MyListener();
        return new ServletListenerRegistrationBean(myListener);
    }

}

思考？@WebServlet(urlPatterns = “/my”)：效果：直接响应，没有经过Spring的拦截器？

1、首先系统中，应该 是有两个servlet:

第一个是MyServlet —> /my

第二个是DispatcherServlet –-> /

2、DispatcherServlet如何注册起来？

• 容器中自动配置了DispatcherServlet 属性，属性绑定到WebMvcProperties
• 如果我们要修改 DispatcherServlet 相关的行为，应该改的就是 对应文件配置项 spring.mvc
• 通过 ServletRegistrationBean 把 DispatcherServlet 配置进来。
• 默认映射的是 / 路径。

Tomcat - Servlet ，如果多个Servlet都能处理同一层路径，精确优先原则

A：/my/

B：/my/hh
就是说如果你传的是 /my ,那就是找Tomcat的，传 / 就找Spring的Servlet