JSTL(JavaServer Page Standard Tag Library)：JSP标准标签库。它封装了JSP应用的通用核心功能。
1.准备工作
使用JSTL前需要下载所需文件，下载地址及安装教材可参阅：http://www.runoob.com/jsp/jsp-jstl.html
测试类 Person.java
public class Person {
private String name;
private String sex;
private int age;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
}
2、c:out标签：类似out.printf(xxx)
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@ taglib uri = "http://java.sun.com/jsp/jstl/core" prefix = "c" %>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<%
request.setAttribute("requestAttribute", "requestValue");
%>
<jsp:useBean id = "per" class = "com.myclass.Person" scope = "request" /> <!-- Person per = new Person()-->
<jsp:setProperty name = "per" property = "name" value = "zhansan"/>
<c:out value = "zhansan"/><br> <!-- out标签直接输出字符串 -->
<c:out value = "${requestAttribute}"></c:out><br> <!-- out标签输出属性-->
<c:out value = "${per.name}"></c:out><br> <!-- out标签输出对象中属性 -->
<!-- 当输出为空时，输出默认值-->
<c:out value = "${requestAttri}" default = "该属性不存在！"/><br> <!-- default设置默认值 -->
<c:out value = "${requestAttri}">该属性不存在</c:out><br> <!-- 标签体设置默认值 -->
<c:out value = "<%=null %>" default = "该属性不存在！"/>
</body>
</html>
3、c:set标签：主要用于设置属性、对象中属性的值。类似setXXX，setAttribute(var,value);
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<%
request.setAttribute("requestAttri", "requestValue");
%>
<jsp:useBean id = "per" class = "com.myclass.Person" scope = "request" /> <!-- Person per = new Person()-->
<c:set var = "test" value = "test"/> <!-- 没有指定属性范围，默认是pageScope -->
${pageScope.test}
<!-- <c:set var = "属性名称" value = "属性值" scope = "属性作用域" /> -->
<c:set var = "sessionName" value = "sessionValue" scope = "session"/> <!-- 在指定范围中设置属性 （value属性设置值） -->
<!-- 相当于session.setAttribute("sessionName","sessionValue") -->
<c:out value = "${sessionName}" />
<!-- <c:set var = "属性名称" scope = "属性作用域"> 属性值 </c:set> -->
<c:set var = "requestName" scope = "request">requestValue</c:set> <!--在指定范围中设置属性 （标签体设置值）-->
<!-- 相当于request.setAttribute("requestName","requestValue") -->
<c:out value = "${requestName}" />
<!-- <c:set target = "对象名称" property = "属性名" value = "属性值"> -->
<c:set target = "${per}" property = "name" value = "zhangsan"/> <!--通过标签 设置对象属性 类似 per.name = "zhangsan"-->
<c:out value="${per.name}"></c:out>
<c:out value="${per}"></c:out> <!-- 此处的${per} 类似 System.out.print(per)-->
</body>
</html>
4、c:remove标签:移除属性，类似（xxx.remove(name)）
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@ page import = "java.util.*,com.myclass.*" %>
<%@ taglib uri = "http://java.sun.com/jsp/jstl/core" prefix = "c" %>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<c:set var = "testRemove" value = "value" scope = "session"/>
<!-- <c:remove var = "属性名" scoep = "[page|request|session|application]" /> 删除指定作用域中的var属性-->
<c:remove var="testRemove" scope="session"/> <!-- 类似 session.removeAttribute("testRemove") -->
<c:out value = "${tempRemove }" default="该属性不存在"/>
</body>
</html>
5、c:if 标签:用于判断，类似if(test == [true | false]){语句}
<%@ taglib uri = "http://java.sun.com/jsp/jstl/core" prefix = "c" %>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<c:set var = "age" value = "19" scope = "session"/>
<%-- <c:if test = "判断条件" var = "属性名" scope = "设置保存范围" /> --%>
<!-- 判断的结果（true|false）会存储在var中 -->
<c:if test = "${age >= 18 }" var="isAdult" scope = "session" >
<h2> 成年</h2> <!-- 满足条件执行的语句 -->
</c:if>
<c:if test = "${!isAdult}" > <!-- !isAdult 和isAdult互反所以只会执行一个 -->
未成年
</c:if>
是否成年：${isAdult}
</body>
</html>
6、c:choose标签:分支选择，类似switch。
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@ page import = "java.util.*,com.myclass.*" %>
<%@ taglib uri = "http://java.sun.com/jsp/jstl/core" prefix = "c" %>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<c:set var = "score" value = "60" scope = "session"/>
<c:choose >
<c:when test="${score >= 90}"> 优秀</c:when> <!-- test为true则执行对应语句并跳出choose -->
<c:when test="${score >= 80}"> 良好</c:when>
<c:when test="${score >= 70}"> 一般</c:when>
<c:when test="${score >= 60}"> 及格</c:when>
<c:otherwise>不及格</c:otherwise> <!-- 所有选项都不满足则执行otherwise中的语句 -->
</c:choose>
</body>
</html>
7、c: forEach标签:主要用于输出可迭代对象和控制迭代次数（for）
实现了Collection接口的对象，都可以使用forEach输出。
<%@ taglib uri = "http://java.sun.com/jsp/jstl/core" prefix = "c" %>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<!-- forEach输出list -->
<%
List<String> list = new LinkedList<String>();
for(int i = 0; i < 5; i++){
list.add("赵" + i);
}
request.setAttribute("list", list);
%>
<c:forEach items = "${list}" var = "li">
<c:out value = "${li}"/><!-- li就代表链表中一个对象（String） -->
</c:forEach><br>
<!-- forEach输出map -->
<%
Map<String,Person> map = new HashMap<String,Person>();
for(int i = 0; i < 5; i++){
map.put("" + i,new Person("钱" + i, i % 2 == 0 ? "man" : "woman", i));
}
request.setAttribute("map",map);
%>
<c:forEach items = "${map}" var = "m" ><!-- m代表map中一个对象，可通过m.key获取键，m.value获取值（person对象） -->
${m.key } ${m.value.name} ${m.value.sex} ${m.value.age}<br>
</c:forEach><br>
<!-- 控制迭代次数 并输出状态-->
<table>
<td>值</td><td> 是否是第一个</td><td>是否是最后一个</td><td>计数（当前是第几个）</td>
<c:forEach var = "i" begin="1" end = "11" step = "2" varStatus="st"> <!-- 步长（step）为2 for(i = 1; i <= 11 ; i += 2 ) -->
<tr><!-- 迭代的属性 当前属性是否是第一个 当前属性是否是最后一个 计数是第几个属性，从1开始-->
<td>${i }</td><td> ${st.first}</td><td>${st.last }</td><td>${st.count}</td>
</tr>
</c:forEach>
</table>
</body>
</html>
8、forTokens标签: 将字符串分割成子串然后迭代。类“www.google.com”.split(".")
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@ page import = "java.util.*,com.myclass.*" %>
<%@ taglib uri = "http://java.sun.com/jsp/jstl/core" prefix = "c" %>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body> <!-- 0 1 2 --> <!--类似 l[3] = {"www","google","com"}; for(i = 0; i <=2 ; i+=2) printf(l[i]) -->
<c:forTokens items="www.google.com" delims="." var = "l" begin = "0" end = "2" step = "2">
${l}<br>
</c:forTokens>
<!-- items为被切割的字符串，delims 为切割的依据 -->
</body>
</html>
9.c:redirect：重定向将重定向到指定URL。
<%@ page language="java" import = "java.util.*,com.myclass.*" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@ taglib uri = "http://java.sun.com/jsp/jstl/core" prefix = "c" %>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<c:redirect url="http://www.baidu.com"></c:redirect> <!-- 重定向到百度 -->
</body>
</html>
参考资料：
https://blog.csdn.net/qq_42246139/article/details/80623607
http://www.runoob.com/jsp/jsp-jstl.html
原文地址：https://www.cnblogs.com/huang-changfan/p/10345924.html
时间： 2024-09-29 09:31:11