servlet的实现

1.servelt的作用
接受请求，对请求进行处理，并发送响应。
2.编写servlet
a.继承HttpServlet这个类(此类实现了Servlet接口)

package servlet;import java.io.IOException;import java.io.UnsupportedEncodingException;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class FirstServlet extends HttpServlet{    @Override    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        // TODO Auto-generated method stub        this.log("执行了doGet方法");        //调用servlet自带的日志输出信息到控制台    }    @Override    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        // TODO Auto-generated method stub        this.log("执行了doPost方法");    }    @Override    protected long getLastModified(HttpServletRequest req) {        // TODO Auto-generated method stub        this.log("执行了lastModified方法");        return -1;    }    private void execute(HttpServletRequest req,HttpServletResponse resp) throws Exception{        resp.setCharacterEncoding("UTF-8");        req.setCharacterEncoding("UTF-8");        String requestURI=req.getRequestURI();        String method=req.getMethod();        //访问该servlet的方式，get或者method        String param=req.getParameter("param");        //客户提交的参数param值    }}

b.在web.xml中配置servlet

<!-- 配置servlet -->  <servlet>    <servlet-name>FirstServlet</servlet-name>    <servlet-class>servlet.FirstServlet</servlet-class>    <!-- 初始化参数 -->    <init-param>        <param-name>message</param-name>        <param-value>welcome to FirstServlet</param-value>    </init-param>    <init-param>        <param-name>encoding</param-name>        <param-value>UTF-8</param-value>    </init-param>    <!-- 配置servlet的加载方式,如果是1的话，tomcat会在启动的时候加载该servlet，否则在有人第一次请求时加载该servlet -->    <load-on-startup>1</load-on-startup>  </servlet>

c.在web.xml中配置servlet-mapping

  <!-- 配置servlet-mapping -->  <servlet-mapping>    <servlet-name>FirstServlet</servlet-name>    <!-- 配置servlet的访问路径 -->    <url-pattern>/FirstServlet</url-pattern>  </servlet-mapping>