Tag标记中使用attribute和variable指令(习题六) --jsp程序设计
一、作业要求:
p59 习题6,求圆和梯形面积
二、源码分析
2.1 lianxi6.jsp
<%--
Created by IntelliJ IDEA.
User: corrine
Date: 2019/3/26
Time: 9:42
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ taglib tagdir="/WEB-INF/tags" prefix="RestTag" %>
<%@ taglib tagdir="/WEB-INF/tags" prefix="CircleTag" %>
<html>
<head>
<title>练习六</title>
</head>
<body>
<h3>以下是调用Rest.tag文件的效果:</h3>
<RestTag:Rect numberA="5" numberB="6"></RestTag:Rect>
<%=RectMessage%>
<%=RectArea%>
<h3>以下是调用Circle.tag文件的效果:</h3>
<CircleTag:Circle number="5"/>
<%=CircleMessage%>
<%=CircleArea%>
</body>
</html>
2.2 Circle.tag
<%@tag pageEncoding="utf-8" %>
<%@attribute name="number" required="true" %>
<%@variable name-given="CircleArea" variable-class="java.lang.Double" scope="AT_END" %>
<%@variable name-given="CircleMessage" scope="AT_END" %>
<%!
static double PI = 3.14;
public double getCircleArea(double a){
if (a!=0){
double area =a*a*PI;
return area;
}else
return -1;
}
%>
<% try{
double a=Double.parseDouble(number);
double result =0;
result = getCircleArea(a);
jspContext.setAttribute("CircleArea",new Double(result));
jspContext.setAttribute("CircleMessage","半径为"+a+"的圆面积为:");
}catch (Exception e){
jspContext.setAttribute("CircleArea",new Double(-1.0));
jspContext.setAttribute("CircleMessage",""+e.toString());
}
%>
2.3 Rect.tag
<%@tag pageEncoding="utf-8" %>
<%@attribute name="numberA" required="true" %>
<%@attribute name="numberB" required="true" %>
<%@variable name-given="RectArea" variable-class="java.lang.Double" scope="AT_END" %>
<%@variable name-given="RectMessage" scope="AT_END" %>
<%!
public double getRectArea(double a,double b){
if (a!=0&&b!=0){
double area =a*b;
return area;
}else
return -1;
}
%>
<% try{
double a=Double.parseDouble(numberA);
double b=Double.parseDouble(numberB);
double result =0;
result = getRectArea(a, b);
jspContext.setAttribute("RectArea",new Double(result));
jspContext.setAttribute("RectMessage","长为"+a+",宽为"+b+"的矩形面积为:");
}catch (Exception e){
jspContext.setAttribute("RectArea",new Double(-1.0));
jspContext.setAttribute("RectMessage",""+e.toString());
}
%>
三、结果图: