第一个servlet小例子

2022-07-20 08:47:47

1、sendForward.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"

    pageEncoding="UTF-8"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

<title>Insert title here</title>

</head>

<body>

    <form action="Verify" method="post">

        请输入一个实数：<input type="text" name="number">

        <input type="submit" value="确定">

    </form>

</body>

</html>

如图所示：

2、servlet类：Verify.java

package servlet;

import java.io.IOException;

import java.io.PrintWriter;

import javax.servlet.RequestDispatcher;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class Verify extends HttpServlet {

    public Verify() {

        super();

    }

    public void destroy() {

        super.destroy(); // Just puts "destroy" string in log

    }

    public void doGet(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        response.setContentType("text/html;charset=UTF-8");

        doPost(request,response);

    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        response.setContentType("text/html;charset=UTF-8");

        String number=request.getParameter("number");

        double n=Double.parseDouble(number);    //上面是String，把String类型转为double类型

        if(n>6000||n<-6000){

            response.sendRedirect("sendForward.jsp");

        }else{

            //转发到另一个servlet文件

            request.getRequestDispatcher("ShowMessage").forward(request, response);

        }

    }

    public void init() throws ServletException {

    }

}

两种重定向方式：

（1）重定向： response.sendRedirect("sendForward.jsp");

（2）请求转发：request.getRequestDispatcher("ShowMessage").forward(request, response);

3、servlet类：ShowMessage.java

package servlet;

import java.io.IOException;

import java.io.PrintWriter;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class ShowMessage extends HttpServlet {

    public ShowMessage() {

        super();

    }

    public void destroy() {

        super.destroy();

    }

    public void doGet(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        response.setContentType("text/html;charset=UTF-8");

        doPost(request,response);

    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        response.setContentType("text/html;charset=UTF-8");

        PrintWriter out=response.getWriter();

        String number=request.getParameter("number");

        double n=Double.parseDouble(number);

        out.println(number+"的平方："+(n*n));

    }

    public void init() throws ServletException {

    }

}

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