JSP(8)—EL案例和JSTL案例
2024-10-18 20:21:56
1.EL案例
el.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@ page import="com.test.bean.Customer" %>
<%@ page import="java.lang.reflect.Method;" %>
<!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>
<!-- 一、使用JavaBean为属性赋值，属性的有效范围为session-->
<jsp:useBean id="customer1" class="com.test.bean.Customer" scope="session"></jsp:useBean>
<jsp:setProperty property="username" name="customer1" value="root"/>
<!-- 获取设置的属性值的三种方式 -->
<!-- 1.使用Java代码 -->
<%
Customer customer2 = (Customer)session.getAttribute("customer1");
out.println("1.username:");
out.println(customer2.getUsername());
%>
<br><br>
<!-- 2.使用JavaBean的getProperty()方法 -->
2.username：<jsp:getProperty property="username" name="customer1"/>
<br><br>
<!-- 3.使用EL表达式 -->
3.username：${sessionScope.customer1.username }
<br><br>
<!-- 二、获取请求参数的值 ${param.username }-->
<form action="el.jsp" method="post">
①回显——使用request对象
usernName:<input type="text" name="username"
value="<%=request.getParameter("username") == null ? "" : request.getParameter("username")%>">
<br><br>②回显——使用EL表达式：
usernName:<input type="text" name="username"
value="${param.username }">
<input type="submit" value="Submit">
<br><br>③使用request对象：
userName:<%=request.getParameter("username") %>
</form>
<br><br>
<!-- 三、跨页面传递参数 -->
<a href="el2.jsp?age=26&name=a&name=b&name=c">To El2 Page</a>
<br><br>
<!-- 四、存储数据范围 -->
<%
Customer customer = new Customer();
customer.setUsername("Ann");
request.setAttribute("customer1", customer);
%>
获取默认范围内的username的值：${customer1.username }
<br><br>
获取session范围内的username的值：${sessionScope.customer1.username }
</body>
</html>el2.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@ page import="com.test.bean.Customer" %>
<!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>
<!-- 五、自动类型变换 -->
age：${param.age }
<br><br>
age：<%=request.getParameter("age")%>
<br><br>
对数据进行加减操作之后：
<br><br>
age：${param.age + 10}
<br><br>
age：<%=request.getParameter("age") + 10%>
<br><br>
<!-- 六、跨页面获取属性值 -->
<!-- 获取设置的属性值的三种方式 -->
<!-- 1.使用Java代码 -->
<%
Customer customer3 = (Customer)session.getAttribute("customer1");
out.println("1.username:");
out.println(customer3.getUsername());
%>
<br><br>
<!-- 2.使用JavaBean的getProperty()方法 -->
<jsp:useBean id="customer1" class="com.test.bean.Customer" scope="session"></jsp:useBean>
2.username：<jsp:getProperty property="username" name="customer1"/>
<br><br>
<!-- 3.使用EL表达式 -->
3.username：${sessionScope.customer1.username }
<br><br>
<!-- 七、隐含对象 -->
<!-- 1、与范围相关的隐含对象pageScope、requestScope、sessionScope、applicationScope -->
<%
application.setAttribute("username", "appName");
session.setAttribute("username", "sesName");
request.setAttribute("username", "reqName");
pageContext.setAttribute("username", "pageName");
%>
<br><br>
pageScope——username：${pageScope.username }
<br><br>
requestScope——username：${requestScope.username }
<br><br>
sessionScope——username：${sessionScope.username }
<br><br>
applicationScope——username：${applicationScope.username }
<br><br>
<!-- 2.与输入有关的隐含对象Param、ParamValues，与五中的自动类型变换获取属性的方式一样 -->
Age(param)：${param.age }
<br><br>
Names(paramValues)：${paramValues.name }
<br><br>
Names(paramValues)：${paramValues.name[0] }
<br><br>
<!-- 3.其他隐含对象 cookie、header、headerValues、initParam、pageContext -->
cookie：${cookie.JSESSIONID.name }——${cookie.JSESSIONID.value }
<br><br>
header：${header["Accept-Language"] }
<br><br>
initParam：${initParam.user }
<br><br>
pageContext即为PageContext类型，但只能读取属性。
pageContext读取contextPath：${pageContext.request.contextPath }
<br><br>
sessionid：${pageContext.session.id }
<br><br>
<!-- 八、运算符 -->
年龄：${param.age }，是${param.age > 18 ? "成年人" : "未成年人" }
<br><br>
<form action="ElFunction.jsp">
<input type="text" name="name" value="test">
<input type="submit" value="To ElFunction Page">
</form>
</body>
</html>ELFunction.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@ taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions" %>
<%@ taglib prefix="test" uri="http://www.Test.com/mytag/core" %>
<!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>
<h3>EL表达式函数</h3>
<!-- 1.使用预定义函数 -->
参数长度：${fn:length(param.name)}
<br><br>
大小写转换：${fn:toUpperCase(param.name) }
<!-- 2.自定义函数 -->
<br><br>
两数相加，和为：${test:concat("10", "10") }
</body>
</html>2.JSTL案例
jstl.jsp
<%@page import="java.util.HashMap"%>
<%@page import="java.util.Map"%>
<%@page import="com.test.bean.Student"%>
<%@page import="com.test.bean.Customer"%>
<%@page import="java.util.List"%>
<%@page import="java.util.ArrayList"%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<%
request.setAttribute("book", "<<Java>>");
Customer customer = new Customer();
customer.setUsername("test");
request.setAttribute("cus", customer);
%>
<form action="jstl.jsp">
<input type="text" name="name" value="test">
<input type="text" name="age" value="23">
<input type="submit" value="Sunbmit">
</form>
<h3>jstl核心标签库，表达式操作</h3>
<!-- 1.out -->
book:${requestScope.book }
<br><br>
book:<c:out value="${requestScope.book}"></c:out>
<br><br>
<!-- 2.set -->
<c:set var="name" value="test" scope="page"></c:set>
<c:set var="name" value="test" scope="request"></c:set>
<c:set var="name" value="${param.name }" scope="session"></c:set>
name1:${pageScope.name }
<br><br>
name2:${requestScope.name }
<br><br>
name3:${sessionScope.name }
<br><br>
<!-- 把请求参数赋给javaBean的属性 -->
name4:${requestScope.cus.username }
<br><br>
<!-- 方案一、使用java代码 -->
<%
String str = request.getParameter("name");
request.setAttribute("username", str);
%>
<!-- 显示结果 -->
name5:${requestScope.cus.username }
<br><br>
<!-- 方案二、使用jstl标签 -->
<c:set target="${requestScope.cus }" property="username" value="${param.name }"></c:set>
<!-- 显示结果 -->
name6:${requestScope.cus.username }
<br><br>
<!-- 3.remove -->
<c:remove var="name" scope="session"/>
<!-- 显示结果 -->
name3(移除属性name3的结果显示):${sessionScope.name }
<br><br>
<h3>jstl核心标签库，流程控制操作</h3>
<!-- 4.if -->
<c:set var="age" value="20" scope="page"></c:set>
<c:if test="${pageScope.age > 18}">成年</c:if>
<br><br>
<c:if test="${pageScope.age > 18}" var="isAdult" scope="page"></c:if>
isAudlt:<c:out value="${pageScope.isAdult}"></c:out>
<br><br>
<!-- 5.choose when otherwise -->
<c:choose>
<c:when test="${param.age > 60 }">老年</c:when>
<c:when test="${param.age > 30 }">中年</c:when>
<c:when test="${param.age > 18 }">青年</c:when>
<c:when test="${param.age < 18 }">少年</c:when>
<c:otherwise>其他...</c:otherwise>
</c:choose>
<br><br>
<h3>jstl核心标签库，流程控制操作</h3>
<!-- 6.c:forEach -->
<!-- 1至10，每隔三个数输出 -->
<c:forEach begin="1" end="10" step="3" var="i" >
${i }、
</c:forEach>
<br><br>
<!-- 遍历集合数据 -->
<%
//List
List<Student> students = new ArrayList<Student>();
students.add(new Student(1,"AA"));
students.add(new Student(2,"BB"));
students.add(new Student(3,"CC"));
students.add(new Student(4,"DD"));
students.add(new Student(5,"EE"));
request.setAttribute("stu", students);
//Map
Map<String, Student> studentMap = new HashMap<String, Student>();
studentMap.put("a", new Student(1, "AAA"));
studentMap.put("b", new Student(2, "BBB"));
studentMap.put("c", new Student(3, "CCC"));
studentMap.put("d", new Student(4, "DDD"));
studentMap.put("e", new Student(5, "EEE"));
request.setAttribute("stuMap", studentMap);
%>
<c:forEach items="${requestScope.stu }" var="student" varStatus="status">
${student.id }、${student.name }、${status.index }、${status.count }、${status.first }、${status.last }、<br>
</c:forEach>
<br><br>
<c:forEach items="${requestScope.stu }" var="student" begin="1" step="2">
${student.id }、${student.name }<br>
</c:forEach>
<br><br>
<c:forEach items="${requestScope.stuMap }" var="student">
${student.key }、${student.value.id }、${student.value.name }<br>
</c:forEach>
<br><br>
<!-- 7.c:forToken -->
<c:set value="a,b,c,d.e.f.g.h" var="test" scope="request"></c:set>
<c:forTokens items="${requestScope.test }" delims="," var="str">
${str }<br>
</c:forTokens>
<br><br>
<h3>jstl核心标签库，URL操作</h3>
<!-- 8.c:import -->
<br><br>
<c:import url="http://www.baidu.com" charEncoding="UTF-8"></c:import>
<br><br>
<!-- 9.c:redirect，从当前页面重定向到指定页面 -->
<!-- 其中/代表的是web应用，所以该操作是服务器跳转，而Servlet中的重定向是客户端跳转 -->
<%--
<c:redirect url="test.jsp"></c:redirect>
<c:redirect url="/demo3_JSTL/test.jsp"></c:redirect>
--%>
<!-- 10.c:url，产生一个url地址 -->
<c:url value="/demo3_JSTL/test.jsp" var="varValue">
<c:param name="name" value="Test你好!"></c:param>
</c:url>
<br><br>
url:${varValue}
</body>
</html>test.jsp
<body>
<h3>重定向到该页面！！</h3>
</body>MyElFunction.java
package com.test.MyElFunction;
/**
* EL表达式自定义函数
*/
public class MyElFunction {
public static String concat(String str1, String str2){
return str1 + str2;
}
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