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JSTL技术
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1．JSTL概述
JSTL（JSP Standard Tag Library)，JSP標準標簽庫，可以嵌入在jsp頁面中使用標簽的形式完成業(yè)務(wù)邏輯等功能。jstl出現(xiàn)的目的同el一樣也是要代替jsp頁面中的腳本代碼。JSTL標準標準標簽庫有5個子庫，但隨著發(fā)展，目前常使用的是他的核心庫
標簽庫標簽庫的URI前綴 Core http://java.sun.com/jsp/jstl/core c I18N http://java.sun.com/jsp/jstl/fmt fmt SQL http://java.sun.com/jsp/jstl/sql sql XML http://java.sun.com/jsp/jstl/xml x Functions http://java.sun.com/jsp/jstl/functions fn
2．JSTL導入
需要導兩個包：
jstl.jar
standar.jar
使用jsp的taglib指令導入核心標簽庫
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
3．JSTL核心庫的常用標簽
1）<c:if test=””>標簽
1）遍歷List的值
2）遍歷List的值
3）遍歷Map<String,String>的值
4）遍歷Map<String,User>的值
5）遍歷Map<User,Map<String,User>>的值
//forEach.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"pageEncoding="UTF-8"%>
<%@ page import="java.util.*" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%@ page import="beyond.domain.*" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
< html> < head> < metahttp-equiv = " Content-Type" content = " text/html; charset=UTF-8" > < title> Insert title here
</ title> </ head> < body> <%//模擬List
< String> strListList
< String> strList = new ArrayList
< String> ();strList.add("beyond0");strList.add("beyond1");strList.add("beyond2");strList.add("beyond3");request.setAttribute("wsq", strList);//遍歷List
< User> 的值List
< User> userList = new ArrayList
< User> ();User user1 = new User();//list集合中的第一個元素user1.setId(2);user1.setName("qibao");user1.setPassword("wsq");userList.add(user1);//list集合中的第二個元素User user2 = new User();user2.setId(3);user2.setName("yanyu");user2.setPassword("wsq");userList.add(user2);application.setAttribute("qb", userList);//遍歷Map
< String,String> 的值Map
< String,String> strMap = new HashMap
< String,String> ();strMap.put("name", "hjj");strMap.put("age", "32");strMap.put("addr", "香港");strMap.put("email", "hjj@qq.com");session.setAttribute("strMap", strMap);//遍歷Map
< String,User> 的值Map
< String,User> userMap = new HashMap
< String,User> ();userMap.put("user1", user1);userMap.put("user2", user2);session.setAttribute("userMap", userMap); /* //遍歷Map<User,Map
< String,User> >的值Map<User,Map
< String,User> > mapMap = new HashMap<User,Map
< String,User> >();mapMap.put(user1,userMap);mapMap.put(user2,userMap);session.setAttribute("mapMap", mapMap); */%>
< h1> 取出strList的數(shù)據(jù)
</ h1> < c: forEachitems = " ${wsq}" var = " str" > ${str}
< br/> </ c: forEach> < h1> 取出userList的數(shù)據(jù)
</ h1> < c: forEachitems = " ${qb}" var = " user" > user的name:${user.name}------------user的password:${user.password}
< br/> </ c: forEach> < h1> 取出strMap的數(shù)據(jù)
</ h1> < c: forEachitems = " ${strMap}" var = " entry" > ${entry.key}---------------${entry.value}
< br/> </ c: forEach> < h1> 取出userMap的數(shù)據(jù)
</ h1> < c: forEachitems = " ${userMap}" var = " entry" > ${entry.key}--------------${entry.value.id}--------------${entry.value.name}--------------${entry.value.password}
< br/> </ c: forEach> <%--
< h1> 取出mapMap的數(shù)據(jù)
</ h1> < c: forEachitems = " ${mapMap}" var = " enter" > ${entry.key.key}--------------${entry.value.value.id}--------------${entry.value.name}--------------${entry.value.password}
< br/> </ c: forEach> --%>
</ body> </ html>
//userLogin.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"pageEncoding="UTF-8"%>
<%@ page import= "beyond.domain.*" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
< html> < head> < metahttp-equiv = " Content-Type" content = " text/html; charset=UTF-8" > < title> Insert title here
</ title> </ head> < body> <% User user = new User();user.setId(1014);user.setName("wsq");user.setPassword("wsq");session.setAttribute("user", user);/* 把user放到session域當中 */%>
</ body> </ html>
//jstl.jsp
<%@ 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 PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
< html> < head> < metahttp-equiv = " Content-Type" content = " text/html; charset=UTF-8" > < title> Insert title here
</ title> </ head> < body> <%request.setAttribute("count", 1014);%>
< c: iftest = " ${count==1014}" > nice you are right！！
</ c: if> < c: iftest = " 1==1" > beyond
</ c: if> < c: iftest = " 1!=1" > sq
</ c: if> < c: forEachbegin = " 0" end = " 5" var = " i" > ${i}
< br/> </ c: forEach> < c: forEachitems = " ${productList}" var = " pro" > ${pro.pname}
</ c: forEach> </ body> </ html> 總結(jié)
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