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JSP学习
一、准备我们心爱的IDEA
new一个项目：New Project --> Next -->Next -->Finsh
二、配置好服务器Tomcat-9.0.30
1.> 在WEB-INF下创建一个Lib包
将jsp-api.jar复制进去，并使其生效
未生效前：
生效过程：
2.> 用锤子配置汤姆猫TomCat
点击+ 号 选择本地的汤姆猫
在Deployment中的 + 号 选择Artifat
将多余的名称删去，为了方便找到
三、编写JSP文件
1.> 在web包下创建以.jsp为后缀名的文件
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html><head><title>$Title$</title></head><body>$END$</body>
</html>
2.>语法
JSP注释：为代码作注释以及将某段代码注释掉。
<%-- 该部分注释在网页中不会被显示--%>
<%-- 注释 --%> JSP注释，注释内容不会被发送至浏览器甚至不会被编译
脚本程序的语法格式：
<% 代码片段 %>
JSP表达式
<%= 表达式 %>
四、写个代码爽一下
运行–前提网址正确
1.>求字符串的长度
<%--Created by IntelliJ IDEA.User: 86156Date: 2023/9/4Time: 10:28To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head><title>案例1--求字符串的长度</title>
</head>
<body><%--java代码在下面的标识里面写入<%%>中--%>
<%String str = "hello";out.println("字符串长度为：" + str.length() + "，字符串：" + str);%>
</body>
</html>
运行结果：
网络：http://localhost:8080/FirstWeb2_war_exploded/strlen.jsp
2.>计算数组平均值
<%--Created by IntelliJ IDEA.User: 86156Date: 2023/9/18Time: 9:15To change this template use File | Settings | File Templates.
--%>
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8" %>
<!DOCTYPE html>
<html>
<head><meta charset="UTF-8"><title>计算平均值</title>
</head>
<body>
<%int arraySize = 5;int[] numbers = new int[arraySize];numbers[0] = 10;numbers[1] = 20;numbers[2] = 30;numbers[3] = 40;numbers[4] = 50;int sum = 0;for (int i = 0; i < arraySize; i++) {sum += numbers[i];}double average = (double) sum / arraySize;
%>平均值是：<%= average %>
</body>
</html>
http://localhost:8080/FirstWeb2_war_exploded/IntARRay.jsp
3.>九九乘法表
方式一：
<%--Created by IntelliJ IDEA.User: 86156Date: 2023/9/11Time: 11:16To change this template use File | Settings | File Templates.
--%><%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8" %>
<!DOCTYPE html>
<html>
<head><style>table {border-collapse: collapse;}th, td {border: 1px solid black;padding: 10px;text-align: center;}.odd {background-color: lightblue;}.even {background-color: lightgreen;}</style>
</head>
<body>
<table><tr><th></th><% for (int i = 1; i <= 9; i++) { %><th><%= i %></th><% } %></tr><% for (int i = 1; i <= 9; i++) { %><tr><th><%= i %></th><% for (int j = 1; j <= 9; j++) { %><% int result = i * j; %><td class="<%= (i + j) % 2 == 0 ? "even" : "odd" %>"><%= i %> * <%= j %> = <%= result %></td><% } %></tr><% } %>
</table>
</body>
</html>
http://localhost:8080/FirstWeb2_war_exploded/multitable1.jsp
方式二：
<%--Created by IntelliJ IDEA.User: 86156Date: 2023/9/11Time: 10:55To change this template use File | Settings | File Templates.
--%>
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8" %>
<!DOCTYPE html>
<html lang="en">
<head><style>table {border-collapse: collapse;}th, td {border: 1px solid black;padding: 10px;text-align: center;}.odd {background-color: lightblue;}.even {background-color: lightgreen;}</style>
</head>
<body>
<table><tr><th></th><% for (int i = 1; i <= 9; i++) { %><th><%= i %></th><% } %></tr><% for (int i = 1; i <= 9; i++) { %><tr><th><%= i %></th><% for (int j = 1; j <= 9; j++) { %><% int result = i * j; %><% if (j >= i) { %><td class="<%= (i + j) % 2 == 0 ? "even" : "odd" %>"><%= i %> * <%= j %> = <%= result %></td><% } else { %><td></td><% } %><% } %></tr><% } %>
</table>
</body>
</html>
http://localhost:8080/FirstWeb2_war_exploded/multitalbe2.jsp
4.>获取圆的面积：
STEP1：编写一个圆的类
在src下，new一个包，包下new一个class文件为circle
如图：
写好私有域的r，利用ptg快速生成JavaBean (ptg可以在插件中下载）
package cn.heima.circle2;public class Circle {private double r;public Circle() {}public Circle(double r) {this.r = r;}/*** 获取* @return r*/public double getR() {return r;}/*** 设置* @param r*/public void setR(double r) {this.r = r;}public String toString() {return "Circle{r = " + r + "}";}public double getAreacIR(){return Math.PI*this.r*this.r;}
}
STEP2：在JSP文件下导入Circle文件：
导入方法
<%@ page import="cn.heima.circle2.Circle" %>
<%--Created by IntelliJ IDEA.User: 86156Date: 2023/9/11Time: 11:27To change this template use File | Settings | File Templates.
--%>
<%--Created by IntelliJ IDEA.User: 86156Date: 2023/9/11Time: 11:27To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ page import="cn.heima.circle2.Circle" %>
<html>
<head><title>CircleDemo</title>
</head>
<body>
<%Circle c = new Circle(1.0);out.print(c.getAreacIR());
%>
</body>
</html>
结果
