上机指导第十二章

绝地灬酷狼 2024-03-30 16:46 12阅读 0赞

输入三角形三条边的长度，计算并显示三角形的面积。

设计分析：

• 界面 JSP：输入三条边（input.jsp），显示三角形面积（show.jsp）；

• 模型 JavaBean：（Triangle.java）判断三条边是否能组成三角形，计算三角形面积；

• 控制器 Servlet：从input.jsp 接收三条边输入的数据，创建响应的JavaBean 实例，验证输入合法性后再计算三角形面积结果发给show.jsp。

思考：如果输入比较复杂，验证合法性工作怎么处理比较好（从功能上考虑）？

package com.inspur.ch12;

import java.io.IOException;

import java.io.UnsupportedEncodingException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import javax.servlet.http.HttpSession;

/\*\*

\*/

public class ComputServlet extends HttpServlet \{

@Override

public void doPost(HttpServletRequest request, HttpServletResponse response)

throws UnsupportedEncodingException, IOException \{

HttpSession session = request.getSession();

// 从input.jsp 接收三条边输入的数据，创建响应的JavaBean 实例，验证输入合法性后再计算三角形面积结果发给show.jsp。

// 如果输入比较复杂，验证合法性工作怎么处理比较好

String length1 = request.getParameter("length1");

String length2 = request.getParameter("length2");

String length3 = request.getParameter("length3");

// if((a+b)>c&&(a+c>b)&&(b+c)>a)

//1.校验输入的三条边是否为大于0的数值

double num1 = 0;

double num2 = 0;

double num3 = 0;

try \{

num1 = Double.parseDouble(length1);

num2 = Double.parseDouble(length2);

num3 = Double.parseDouble(length3);

\} catch (NumberFormatException e) \{

session.setAttribute("error", "输入的三条边的长度必须为大于0的数值");

response.sendRedirect(request.getContextPath() + "/input.jsp");

return;

if(num1<=0||num2<=0||num3<=0)\{

session.setAttribute("error", "输入的三条边的长度必须为大于0的数值");

response.sendRedirect(request.getContextPath() + "/input.jsp");

return;

//2.校验是否能组成三角形

Triangle triangle = new Triangle();

boolean isTriangle = triangle.isTrTriangle(num1, num2, num3);

if (!isTriangle) \{

session.setAttribute("error", "输入的三条边的长度不能组成三角形，必须任何两条边之和大于第三边");

response.sendRedirect(request.getContextPath() + "/input.jsp");

return;

//3.计算面积

double area=triangle.computArea(num1,num2,num2);

session.setAttribute("area", area);

response.sendRedirect(request.getContextPath() + "/show.jsp");

package com.inspur.ch12;

/\*\*

\* 判断三条边是否能组成三角形，计算三角形面积；

\*/

public class Triangle \{

/\*\*

\* 判断三条边是否能组成三角形

\* @return 如果能组成三角形则返回true，否则返回false

\*/

public boolean isTrTriangle(double num1, double num2, double num3) \{

if ((num1 + num2) > num3 && (num1 + num3) > num2

&& (num2 + num3) > num1) \{

return true;

return false;

/\*\*

\* 计算面积

\* @return 面积

\*/

public double computArea(double num1, double num2, double num3) \{

double area = 0.0;

double p = (num1 + num2 + num3) / 2;

area = Math.sqrt(p \* (p - num1) \* (p - num2) \* (p - num3));

return area;

<%@ page language="java" import="java.util.\*" pageEncoding="UTF-8"%>

String path = request.getContextPath();

String basePath = request.getScheme() + "://"

\+ request.getServerName() + ":" + request.getServerPort()

\+ path + "/";

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

<html>

<head>

<title>接收三条边输入的数据</title>

</head>

<body>

<font color="red"> $\{sessionScope.error \} </font>

<hr>

<h2>请输入三角形的三条边的长度</h2>

<p>

请输入第一条边长度：<input type="text" name="length1">

</p>

<p>

请输入第二条边长度：<input type="text" name="length2">

</p>

<p>

请输入第三条边长度：<input type="text" name="length3">

</p>

<p>

</p>

</form>

<br>

</body>

</html>

<%@ page language="java" import="java.util.\*" pageEncoding="UTF-8"%>

String path = request.getContextPath();

String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

<html>

<head>

<title>显示用户名</title>

</head>

<body>

<p>该三角形的面积：<%=session.getAttribute("area") %></p>

</body>

</html>

<?xml version="1.0" encoding="UTF-8"?>

<web-app version="2.5" xmlns="[http://java.sun.com/xml/ns/javaee"][http_java.sun.com_xml_ns_javaee]

xmlns:xsi="[http://www.w3.org/2001/XMLSchema-instance"][http_www.w3.org_2001_XMLSchema-instance]

xsi:schemaLocation="[http://java.sun.com/xml/ns/javaee][http_java.sun.com_xml_ns_javaee]

[" target="\_blank">http://java.sun.com/xml/ns/javaee/web-app\_2\_5.xsd">][target_blank_http_java.sun.com_xml_ns_javaee_web-app_2_5.xsd]

<servlet-name>computServlet</servlet-name>

<servlet-class>com.inspur.ch12.ComputServlet</servlet-class>

</servlet>

<servlet-mapping>

<servlet-name>computServlet</servlet-name>

<url-pattern>/computServlet</url-pattern>

</servlet-mapping>

</web-app>

[http_java.sun.com_xml_ns_javaee]: http://java.sun.com/xml/ns/javaee
[http_www.w3.org_2001_XMLSchema-instance]: http://www.w3.org/2001/XMLSchema-instance
[target_blank_http_java.sun.com_xml_ns_javaee_web-app_2_5.xsd]: http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd