jstl标签库的配置
* 将jstl.jar和standard.jar拷贝到WEB-INF/lib下（如果使用el表达式，不用拷贝这两个jar）
注意：jstl必须在能够支持j2ee1.4/servlet2.4/jsp2.0版本上的容器才能运行，这个环境
是目前较为常用的环境
标签库的使用
* 采用taglib指令引入
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<%@ taglib prefix="fmt" uri="http://java.sun.com/jsp/jstl/fmt"%>
jstl核心库(core)
Action
package com.lanjh.struts.action;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.struts.action.Action;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;
import com.lanjh.struts.po.Group;
import com.lanjh.struts.po.User;
public class JstlCoreAction extends Action {
@Override
public ActionForward execute(ActionMapping mapping, ActionForm form,
HttpServletRequest request, HttpServletResponse response)
throws Exception {
request.setAttribute("hello", "hello world");
//html文本
request.setAttribute("bj", "<font color='red'>北京欢迎您</font>");
//测试条件控制标签
request.setAttribute("v1", 1);
request.setAttribute("v2", 2);
request.setAttribute("v3", new ArrayList());
request.setAttribute("v4", "test");
//测试c:forEach
Group group = new Group();
group.setName("尚学堂");
List userList = new ArrayList();
for (int i=0; i<10; i++) {
User user = new User();
user.setUsername("user_" + i);
user.setAge(18+i);
user.setGroup(group);
userList.add(user);
}
request.setAttribute("userlist", userList);
//测试循环输出map
Map<String, String> map = new HashMap<String, String>();
map.put("k1", "lanjh");
map.put("k2", "chenj");
request.setAttribute("mapvalue", map);
//测试c:forTokens
request.setAttribute("strTokens", "1,2,3,4,5,6");
return mapping.findForward("success");
}
}
struts配置
<action path="/jstlcore"
type="com.lanjh.struts.action.JstlCoreAction">
<forward name="success" path="/jstl_core.jsp"></forward>
</action>
JSP页面
<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>测试jstl核心库</title>
</head>
<body>
<h1>
测试EL表达式
</h1>
<br>
<hr>
<li>
测试c:out
</li>
<br>
hello(default):
<c:out value="${hello}"></c:out>
<br>
hello(default=123):
<c:out value="${hello}" default="123"></c:out>
<br>
<!-- value值为空或者null时，取default的默认值 -->
hello(default=123):
<c:out value="${hello1}">123</c:out>
<br>
bj(default):
<c:out value="${bj}"></c:out>
<br>
bj(escapeXml="true"):
<c:out value="${bj}" escapeXml="true"></c:out>
<br>
<!-- 解析xml格式的数据 -->
bj(escapeXml="false"):
<c:out value="${bj}" escapeXml="false"></c:out>
<br>
<p>
<li>
测试c:set和c:remove
</li>
<br>
<c:set value="123" var="temp"></c:set>
temp:${temp }
<br>
<c:remove var="temp" />
temp:${temp }
<br>
<p>
<li>
测试条件控制标签c:if
</li>
<br>
<c:if test="${v1 lt v2}" var="v">
v1小于v2<br>
v=${v }
</c:if>
<c:if test="${empty v3}">
v3为空<br>
</c:if>
<c:if test="${!empty v4}">
v4不为空<br>
</c:if>
<p>
<li>
测试条件控制标签c:choose,c:when,c:otherwise
</li>
<br>
<c:choose>
<c:when test="${v1 lt v2}">
v1小于v2<br>
</c:when>
<c:otherwise>
v1大于v2<br>
</c:otherwise>
</c:choose>
<c:choose>
<c:when test="${empty v4}">
v4为空<br>
</c:when>
<c:otherwise>
v4不为空<br>
</c:otherwise>
</c:choose>
<p>
<li>
测试循环控制标签c:forEach
</li>
<br>
<table border="1">
<tr>
<td>
姓名
</td>
<td>
年龄
</td>
<td>
所属组
</td>
</tr>
<c:choose>
<c:when test="${empty userlist}">
<tr>
<td colspan="3">
没有符合条件的数据!
</td>
</tr>
</c:when>
<c:otherwise>
<c:forEach items="${userlist}" var="u">
<tr>
<td>
${u.username }
</td>
<td>
${u.age }
</td>
<td>
${u.group.name }
</td>
</tr>
</c:forEach>
</c:otherwise>
</c:choose>
</table>
<p>
<li>
测试循环控制标签c:forEach,varstatus
</li>
<br>
<table border="1">
<tr>
<td>
姓名
</td>
<td>
年龄
</td>
<td>
所属组
</td>
</tr>
<c:choose>
<c:when test="${empty userlist}">
<tr>
<td colspan="3">
没有符合条件的数据!
</td>
</tr>
</c:when>
<c:otherwise>
<c:forEach items="${userlist}" var="user" varStatus="vs">
<c:choose>
<c:when test="${vs.count % 2 == 0}">
<tr bgcolor="red">
</c:when>
<c:otherwise>
<tr>
</c:otherwise>
</c:choose>
<td>
<c:out value="${user.username}" />
</td>
<td>
<c:out value="${user.age}" />
</td>
<td>
<c:out value="${user.group.name}" />
</td>
</tr>
</c:forEach>
</c:otherwise>
</c:choose>
</table>
<p>
<li>测试循环控制标签c:forEach，普通循环</li><br>
<c:forEach begin="1" end="10">
a<br>
</c:forEach>
<p>
<li>测试循环控制标签c:forEach，输出map</li><br>
<c:forEach items="${mapvalue}" var="v">
${v.key }=${v.value }<br>
</c:forEach>
<p>
<li>测试循环控制标签c:forTokens</li><br>
<c:forTokens items="${strTokens}" delims="," var="v">
${v }<br>
</c:forTokens>
<p>
<li>测试c:catch</li><br>
<%
try {
Integer.parseInt("asdfsdf");
}catch(Exception e) {
out.println(e.getMessage());
}
%>
<p>
<c:catch var="exinfo">
<%
Integer.parseInt("asdfsdf");
%>
</c:catch>
${exinfo }<br>
<p>
<li>测试c:import</li><br>
<!-- 引入外部url地址 -->
<c:import url="http://localhost:8080/struts_login"/>
<p>
<li>测试c:url和c:param</li><br>
<!-- 给url后面加参数 -->
<c:url value="http://localhost:8080/drp/sysmgr/user_add.jsp" var="v">
<c:param name="username" value="Jack"/>
<c:param name="age" value="20"/>
</c:url>
${v }<br>
</body>
</html>