小峰servlet/jsp（6）jstl核心标签库
一、引入jstl
需要jstl.jar;standard.jar;
二、jstl核心标签库：
c:out 内容输出标签;
c:set 用来设置4种属性范围值的标签；
c:remove 用来删除指定范围中的属性；
c:catch 用来处理程序中产生的异常；
c:if 用来条件判断;
c:choose/c:when/c:otherwise 用来多条件判断;
c:forEach 用来遍历数组或者集合;
c:fortokens 分隔输出;
c:import 导入页面;
c:url 生成一个url地址;
c:redirect 客户端跳转
c:out:
1 <%@ page language="java" contentType="text/html; charset=UTF-8" 2 pageEncoding="UTF-8"%> 3 <%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%> 4 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 5 <html> 6 <head> 7 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 8 <title>Insert title here</title> 9 </head> 10 <body> 11 <% 12 pageContext.setAttribute("people","张三"); 13 %> 14 <h2><c:out value="${people}"></c:out></h2> 15 <h2><c:out value="${people2}" default="某人"></c:out></h2> 16 </body> 17 </html>
c:set
1 <body> 2 <c:set var="people" value="张三" scope="request"></c:set> 3 <h2><c:out value="${people}"></c:out></h2> 4 <jsp:useBean id="people2" class="com.java1234.model.People" scope="page"></jsp:useBean> 5 <c:set property="id" target="${people2 }" value="007"></c:set> 6 <c:set property="name" target="${people2 }" value="王二小"></c:set> 7 <c:set property="age" target="${people2 }" value="16"></c:set> 8 <h2>编号：${people2.id }</h2> 9 <h2>姓名：${people2.name }</h2> 10 <h2>年龄：${people2.age }</h2> 11 </body>
c:remove:
1 <body> 2 <c:set var="people" value="张三" scope="request"></c:set> 3 <h2><c:out value="${people}" default="没人啊"></c:out></h2> 4 <c:remove var="people" scope="request"/> 5 <h2><c:out value="${people}" default="没人啊"></c:out></h2> 6 </body>
c:catch:
1 <body> 2 <c:catch var="errMsg"> 3 <% 4 int a=1/0; 5 %> 6 </c:catch> 7 <h2>异常信息：${errMsg }</h2> 8 </body>
c:if:
1 <body> 2 <jsp:useBean id="people" class="com.java1234.model.People" scope="page"></jsp:useBean> 3 <c:set property="id" target="${people }" value="007"></c:set> 4 <c:set property="name" target="${people }" value="王二小"></c:set> 5 <c:set property="age" target="${people }" value="16"></c:set> 6 <c:if test="${people.name=='王二小' }" var="r" scope="page"> 7 <h2>是王二小</h2> 8 </c:if> 9 <c:if test="${people.age<18 }"> 10 <h2>是未成年</h2> 11 </c:if> 12 </body>
c:choose/c:when/c:otherwise: 多条件判断:
1 <body> 2 <jsp:useBean id="people" class="com.java1234.model.People" scope="page"></jsp:useBean> 3 <c:set property="id" target="${people }" value="007"></c:set> 4 <c:set property="name" target="${people }" value="王二小"></c:set> 5 <c:set property="age" target="${people }" value="19"></c:set> 6 <c:choose> 7 <c:when test="${people.age<18 }"> 8 <h2>小于18</h2> 9 </c:when> 10 <c:when test="${people.age==18 }"> 11 <h2>等于18</h2> 12 </c:when> 13 <c:otherwise> 14 <h2>大于18</h2> 15 </c:otherwise> 16 </c:choose> 17 </body>
c:forEach:
1 <%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> 2 <%@ page import="com.java1234.model.*"%> 3 <%@ page import="java.util.*"%> 4 <%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%> 5 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 6 <html> 7 <head> 8 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 9 <title>Insert title here</title> 10 </head> 11 <body> 12 <% 13 String dogs[]={"小黑","小黄","小白","小小"}; 14 pageContext.setAttribute("dogs",dogs); 15 %> 16 <c:forEach var="dog" items="${dogs }"> 17 ${dog } 18 </c:forEach> 19 <hr/> 20 <c:forEach var="dog" items="${dogs }" step="2"> 21 ${dog } 22 </c:forEach> 23 <hr/> 24 <c:forEach var="dog" items="${dogs }" begin="1" end="2"><!--begin end是索引值--> 25 ${dog } 26 </c:forEach> 27 <hr/> 28 <% 29 List<People> pList=new ArrayList<People>(); 30 pList.add(new People(1,"张三",10)); 31 pList.add(new People(2,"李四",20)); 32 pList.add(new People(3,"王五",30)); 33 pageContext.setAttribute("pList",pList); 34 %> 35 <table> 36 <tr> 37 <th>编号</th> 38 <th>姓名</th> 39 <th>年龄</th> 40 </tr> 41 <c:forEach var="p" items="${pList }"> 42 <tr> 43 <td>${p.id }</td> 44 <td>${p.name }</td> 45 <td>${p.age }</td> 46 </tr> 47 </c:forEach> 48 </table> 49 </body> 50 </html>
c:forTokens: 分隔输出：
1 <body> 2 <% 3 String str1="www.java1234.com"; 4 String str2="张三，李四，王五"; 5 pageContext.setAttribute("str1",str1); 6 pageContext.setAttribute("str2",str2); 7 %> 8 <c:forTokens items="${str1 }" delims="." var="s1"> 9 ${s1 } 10 </c:forTokens> 11 <hr/> 12 <c:forTokens items="${str2 }" delims="，" var="s2"> 13 ${s2 } 14 </c:forTokens> 15 </body>
c:import: 导入页面; 有点像jsp include：
1 <body> 2 <c:import url="c_forEach.jsp"></c:import> 3 <c:import url="c_if.jsp"></c:import> 4 </body>
c:url：
1 <body> 2 <c:url value="http://www.baidu.com" var="url"> 3 <c:param name="name" value="xiaoming"></c:param> 4 <c:param name="age" value="26"></c:param> 5 </c:url> 6 <a href="${url }">百度</a> 7 </body>
c:redirect 客户端跳转：
1 <body> 2 <c:redirect url="target.jsp"> 3 <c:param name="name" value="xiaoming"></c:param> 4 <c:param name="age" value="26"></c:param> 5 </c:redirect> 6 </body> 7 8 target.jsp: 9 <body> 10 <h2>姓名：${param.name }</h2> 11 <h2>年龄：${param.age }</h2> 12 </body>
