inputNumber.jsp頁面代碼<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%><%@ taglib tagdir="/WEB-INF/tags" prefix="computer" %><html><body><h2>輸入運算數、選擇運算符號:</h2><form action="" method="post"><input type="text" name="num1" /><select name="operator"><option value="+">+<option value="-">-<option value="*">*<option value="/">/</select><input type="text" name="num2" /><br /><br /><input type="submit" value="提交你的選擇"/></form><% request.setCharacterEncoding("utf-8"); String a = request.getParameter("num1"); String b = request.getParameter("num2"); String operator = request.getParameter(operator); if(a==null) a=""; if(b==null) b=""; if(a.length()>0&&b.length()>0){%><computer: Computer numberA="<%=a %>" numberB="<%=b %>" operator="<%=operator %>" />計算結果:<%=a %><%=operator %><%=b %><%=result %><%}%></body></html>Computer.tag頁面代碼<%@ tag pageEncoding="utf-8" %><%@ attribute name="numberA" required="true" %><%@ attribute name="numberB" required="true" %><%@ attribute name="operator" required="true" %><%@ variable name-given="result" scope="AT_END" %><% try{ double a = Double.parseDouble(numberA); double b = Double.parseDouble(numberB); double r = 0; if(operator.equals("+")) r=a+b; if(operator.equals("-")) r=a-b; if(operator.equals("*")) r=a*b; if(operator.equals("/")) r=a/b; jspContext.setAttribute("result", String.valueOf(r)); }catch(Exception e){ jspContext.setAttribute("result", "發生異常:"+e); }%>
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