Servlet配置方式：

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
*   name servlet的名字 等同  <servlet-name>A</servlet-name>
*   urlPatterns    等同  <url-pattern>/A</url-pattern>
*/

@WebServlet(name="A",urlPatterns="/A")
public class A extends HttpServlet{

@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
  }

@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
  }

}

 filter 配置方式

import java.io.IOException;

import javax.servlet.annotation.WebFilter;

import com.sun.net.httpserver.Filter;
import com.sun.net.httpserver.HttpExchange;

/**
*   filterName filter的名字 等同  <filter-name>A</filter-name>  可以省略
*   urlPatterns    等同  <url-pattern>*</url-pattern>
*/

@WebFilter(filterName="A",urlPatterns="*")
public class A extends Filter{

@Override
public String description() {
return null;
  }

@Override
public void doFilter(HttpExchange arg0, Chain arg1) throws IOException {

  }


}

Listener 配置方式

 
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.annotation.WebListener;

/**
* 使用@WebListener注解将实现了ServletContextListener接口的MyServletContextListener标注为监听器
*/
@WebListener
public class A implements ServletContextListener {

@Override
public void contextDestroyed(ServletContextEvent sce) {
System.out.println("ServletContex销毁");
    }

@Override
public void contextInitialized(ServletContextEvent sce) {
System.out.println("ServletContex初始化");
    }
}