题目：
页面1：显示如下信息
下拉列表：
1.计算三角形
2.计算矩形
3.计算梯形
按钮：计算（submit按钮，提交到页面2）
页面2：根据选项1，2，3
分别收集三角形3条边、矩形2条边、梯形4条边和高的信息
提交按钮（提交给serlet）
servlet：
根据选项和提交的数据，计算相应图形的周长和面积
显示：xxx形，它的边长和高，分别是，周长是，面积是
因为各浏览器编码不同，与servlet编码冲突。为防止出现乱码，所以在这里表达全用了英语。
两个jsp文件由于习惯性的放进了一个作业文件夹里，所以在form表单向servlet传参时用到了 ../ 然后~~~，servlet真好用，比上次的javabean更方便
页面1：frist.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 name="f1" method="post" action="second.jsp">
下拉列表：
<select name="se1">
<option value ="sanjiao">计算三角形</option>
<option value ="juxing">计算矩形</option>
<option value ="tixing">计算梯形</option>
</select>
<input type="submit" name="s1" value="计算">
</form>
</body>
</html>
页面2：second.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@ page import="java.util.*"%>
<!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>
<%
request.setCharacterEncoding("utf-8");
String type;
type = request.getParameter("se1");
if (type.equals("sanjiao")) {
%>
<form name="f1" method="post" action="../solve">
请输入三角形的三条边：<br>
<input type="text" name="b1"><br>
<input type="text" name="b2"><br>
<input type="text" name="b3">
<input type="submit" name="s1" value="提交" />
</form>
<%
} else if (type.equals("juxing")) {
%>
<form name="f1" method="post" action="../solve">
请输入矩形的长和宽： <br>
<input type="text" name="b1"><br>
<input type="text" name="b2">
<input type="submit" name="s1" value="提交" />
</form>
<%
} else if (type.equals("tixing")) {
%>
<form name="f1" method="post" action="../solve">
请输入梯形的四条边和高：<br>
上底 ：<input type="text" name="b1"><br>
下底 ：<input type="text" name="b2"><br>
斜边 ：<input type="text" name="b3"><br>
斜边 ：<input type="text" name="b4"><br>
高 ：<input type="text" name="h">
<input type="submit" name="s1" value="提交" />
<%
}
%>
</body>
</html>
servlet：solve.java
package anyi;
import java.io.IOException;
import java.io.PrintWriter;
import java.lang.Math;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class CalculateMulti2
*/
@WebServlet("/solve")
public class solve extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public solve() {
super();
// TODO Auto-generated constructor stub
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
response.setCharacterEncoding("utf-8");
double b1 = 0, b2 = 0, b3 = 0, b4 = 0, h = 0;
b1 = Integer.parseInt(request.getParameter("b1"));
b2 = Integer.parseInt(request.getParameter("b2"));
try{
b3 = Integer.parseInt(request.getParameter("b3"));
} catch (Exception e) {
}
try{
b4 = Integer.parseInt(request.getParameter("b4"));
h = Integer.parseInt(request.getParameter("h"));
} catch (Exception e) {
}
PrintWriter pw = response.getWriter();
pw.print("<html><body><br>");
pw.print("My name is solve, which is a servlet object.<br><br>");
pw.print("I am responsible for calculating the perimeter and area of the graphics you provided:<br><br>");
if (b3 == 0) {
pw.print("rectangle The side lengths are "+b1+" and "+b2);
pw.print("<br><br> perimeter:" + (b1 + b2) * 2 + " area:" + (b1 * b2));
} else if (b4 == 0) {
pw.print("triangle The side lengths are "+b1+" and "+b2+" and "+b3);
double p=(b1+b2+b3)/2;
double s=Math.sqrt(p*(p-b1)*(p-b2)*(p-b3));
pw.print("<br><br> perimeter:" + (b1 + b2 + b3) + " area:" + s);
}else {
pw.print("trapezoid The side lengths are "+b1+" and "+b2+" and "+b3+" and "+ b4+". height is "+h);
pw.print("<br><br> perimeter:" + (b1 + b2 + b3 + b4) + " area:" + (b1 + b2)*h);
}
pw.print("</body></html>");
}
}
就问题而言，由于页面2传参数量不确定，但又差的个数不多，所以这里分别用了两个try-catch接收可能要接收的值，避免500。其他好像没什么可说的。快期末了要好好学习呀~！