在早期jsp的开发中会用到大量的Scriptlet代码，这样造成了jsp页面维护性和可读性的下降，而Struts所带的标签库在一定程度上解决了此问题，所以我们提倡使用标签而不是用Scriptlet。
二、logic标签
1.<logic:present>与<logic:notPresent>
判断是否有指定属性存在/不存在指定锝范围之中
如果不指定范围，则表示要进行全面锝查找
<%
@ page language="java" pageEncoding="utf-8"%>
<%@ taglib uri="http://struts.apache.org/tags-bean" prefix="bean" %>
<%@ taglib uri="http://struts.apache.org/tags-html" prefix="html" %>
<%@ taglib uri="http://struts.apache.org/tags-logic" prefix="logic" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html:html lang="true">
<head>
<title>logic01.jsp</title>
</head>
<body>
<%
request.setAttribute("name","illu");
session.setAttribute("userId","5");
%>
<logic:present name="name" scope="request">
<h1>指定属性存在 ${name}</h1>
</logic:present>
<logic:notPresent name="name" scope="request">
<h1>指定属性不存在</h1>
</logic:notPresent>
<logic:present name="userId" scope="session">
<h1>指定属性存在 ${userId}</h1>
</logic:present>
<logic:notPresent name="userId" scope="session">
<h1>指定属性不存在</h1>
</logic:notPresent>
</body>
</html:html>2.逻辑判断
a. = <logic:equal>
b. != <logic:notEqual>
c. >= <logic:greaterEqual>
d. <= <logic:lessEqual>
e. > <logic:greaterThan>
f. < <logic:lessThan>
<%@ page language="java" pageEncoding="utf-8"%>
<%@ taglib uri="http://struts.apache.org/tags-bean" prefix="bean" %>
<%@ taglib uri="http://struts.apache.org/tags-html" prefix="html" %>
<%@ taglib uri="http://struts.apache.org/tags-logic" prefix="logic" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html:html lang="true">
<head>
<title>logic02.jsp</title>
</head>
<body>
<%
request.setAttribute("num",new Character('1'));
%>
<logic:equal value="1" name="num" scope="request">
<h1>内容等于1</h1>
</logic:equal>
<logic:notEqual scope="request" name="num" value="1">
<h1>内容不为1</h1>
</logic:notEqual>
<logic:greaterEqual name="num" scope="request" value="1">
<h1>内容大于等于1</h1>
</logic:greaterEqual>
<logic:lessEqual name="num" scope="request" value="1">
<h1>内容小于等于1</h1>
</logic:lessEqual>
<logic:greaterThan name="num" scope="request" value="1">
<h1>内容大于1</h1>
</logic:greaterThan>
<logic:lessThan name="num" scope="request" value="1">
<h1>内容小于1</h1>
</logic:lessThan>
</body>
</html:html>
3.<logic:iterate>迭代标签
<logic:iterate id="集合中对象的使用名称" name="属性名称" scope="存储范围" property="对象属性名称"></logic:iterate>
a.遍历Set
<%@ page language="java" pageEncoding="utf-8"%>
<%@ page import="java.util.*"%>
<%@ taglib uri="http://struts.apache.org/tags-bean" prefix="bean" %>
<%@ taglib uri="http://struts.apache.org/tags-html" prefix="html" %>
<%@ taglib uri="http://struts.apache.org/tags-logic" prefix="logic" %>
<%@ taglib uri="http://struts.apache.org/tags-tiles" prefix="tiles" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html:html lang="true">
<head>
<title>logic03.jsp</title>
</head>
<body>
<%
Set set = new HashSet();
set.add("illu");
set.add("stephen");
set.add("why");
request.setAttribute("names",set);
%>
<logic:iterate id="name" name="names" scope="request">
<h3><bean:write name="name"/>
</logic:iterate>
</body>
</html:html>
b.遍历List
<%@ page language="java" pageEncoding="utf-8"%>
<%@ page import="java.util.*" %>
<%@ taglib uri="http://struts.apache.org/tags-bean" prefix="bean" %>
<%@ taglib uri="http://struts.apache.org/tags-html" prefix="html" %>
<%@ taglib uri="http://struts.apache.org/tags-logic" prefix="logic" %>
<%@ taglib uri="http://struts.apache.org/tags-tiles" prefix="tiles" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html:html lang="true">
<head>
<title>logic04.jsp</title>
</head>
<body>
<%
List list = new ArrayList();
list.add("illu");
list.add("stephen");
list.add("why");
request.setAttribute("names",list);
%>
<logic:iterate id="name" name="names" scope="request">
<h3><bean:write name="name"/></h3>
</logic:iterate>
</body>
</html:html>
c.遍历Map
<%@ page language="java" pageEncoding="utf-8"%>
<%@ page import="java.util.*" %>
<%@ taglib uri="http://struts.apache.org/tags-bean" prefix="bean" %>
<%@ taglib uri="http://struts.apache.org/tags-html" prefix="html" %>
<%@ taglib uri="http://struts.apache.org/tags-logic" prefix="logic" %>
<%@ taglib uri="http://struts.apache.org/tags-tiles" prefix="tiles" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html:html lang="true">
<head>
<title>logic05.jsp</title>
</head>
<body>
<%
Map map = new HashMap();
map.put("illu","4");
map.put("why","3");
map.put("stephen","7");
request.setAttribute("names",map);
%>
<logic:iterate id="name" name="names" scope="request">
<h3><bean:write name="name" property="key"/>--><bean:write name="name" property="value"/></h3>
</logic:iterate>
</body>
</html:html>
d.遍历集合套集合
<%@ page language="java" pageEncoding="ISO-8859-1"%>
<%@ page import="java.util.*" %>
<%@ taglib uri="http://struts.apache.org/tags-bean" prefix="bean" %>
<%@ taglib uri="http://struts.apache.org/tags-html" prefix="html" %>
<%@ taglib uri="http://struts.apache.org/tags-logic" prefix="logic" %>
<%@ taglib uri="http://struts.apache.org/tags-tiles" prefix="tiles" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html:html lang="true">
<head>
<title>logic07.jsp</title>
</head>
<body>
<%
Map map = new HashMap();
List asia = new ArrayList();
asia.add("China");
asia.add("Japan");
asia.add("Korea");
map.put("asia",asia);
List europe = new ArrayList();
europe.add("Britain");
europe.add("Italy");
europe.add("France");
map.put("europe",europe);
request.setAttribute("names",map);
%>
<logic:iterate id="temp" name="names" scope="request">
<h2><bean:write name="temp" property="key"/></h2>
<logic:iterate id="name" name="temp" property="value" scope="page">
<h4><bean:write name="name"/></h4>
</logic:iterate>
</logic:iterate>
</body>
</html:html>
每天进步一点点
posted on 2008-08-07 23:22
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