创建HttpServlet的基本步骤

A．导入包：
    import java.io.*;
    import javax.servlet.*;
    import javax.servlet.http.*;

B．继承HttpServlet类：
　 public class ××× extends HttpServlet

C．覆盖doPost()、doGet()方法：
    public void doPost(HttpServletRequest request,HttpServletResponse response)
            throws IOException,ServletException{…}
    public void doGet(HttpServletRequest request,HttpServletResponse response)
            throws IOException,ServletException{…}

D．获取请求参数：
    String param1 = request.getParameter();

E．创建输出对象：
    PrintWriter out = response.getWriter();

F．设置响应类型：
    response.setContentType();

G．输出响应内容：
　 out.println();