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[JSP] jsp 自定义标签实例

开发技术 开发技术 发布于:2021-10-24 12:00 | 阅读数:334 | 评论:0

分三步:
一、在WEB-INF 下建一个名为tlds的文件夹,再建一个tld文件,如 formatTime.tld,内容为:
<?xml version="1.0" encoding="ISO-8859-1" ?> 
<!DOCTYPE taglib PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.1//EN" 
"https://java.sun.com/j2ee/dtds/web-jsptaglibrary_1_1.dtd"> 
<taglib> 
<tlibversion>1.0</tlibversion> 
<jspversion>1.1</jspversion> 
<shortname>ntuc</shortname> 
<tag> 
<name>formatTimeAsString</name> 
<tagclass>com.ufinity.taglibTest.FormatTimeTag</tagclass> 
<bodycontent>empty</bodycontent> 
<attribute> 
<name>timestamp</name> 
</attribute> 
<attribute> 
<name>format</name> 
</attribute> 
<attribute> 
<name>showTH</name> 
</attribute> 
<attribute> 
<name>style</name> 
</attribute> 
</tag> 
</taglib>
二、建一个class,内容为:
package com.ufinity.taglibTest; 
import java.io.IOException; 
import java.text.DateFormat; 
import java.text.ParseException; 
import java.text.SimpleDateFormat; 
import java.util.Calendar; 
import java.util.Date; 
import java.util.Locale; 
import javax.servlet.jsp.tagext.TagSupport; 
/** 
* Description of the class 
* 
* @author Wangqy 
* @version 1.0 
* @since 2009-8-25 
*/ 
public class FormatTimeTag extends TagSupport { 
/** 
* serialVersionUID long 
*/ 
private static final long serialVersionUID = 8757501937718830491L; 
private String timestamp; 
private String format; 
private String showTH; 
private String style; 
public int doEndTag() 
{ 
try 
{ 
String info = this.convertDateTime(timestamp, format, Boolean.parseBoolean(showTH), style); 
pageContext.getOut().println(info); 
} 
catch (IOException e) { 
} 
return EVAL_PAGE; 
} 
private String convertDateTime(String dateTime, String formater, boolean showTH, String caseStyle) { 
String timePosted = null; 
SimpleDateFormat dateFm = null; 
DateFormat format = new SimpleDateFormat("yyyyMMddHHmmss"); 
Date formatTime = null; 
try { 
formatTime = format.parse(dateTime); 
} catch (ParseException e) { 
return null; 
} 
Calendar calendar = Calendar.getInstance(); 
calendar.setTime(formatTime); 
if (showTH) { 
int day = calendar.get(Calendar.DAY_OF_MONTH); 
String daySuffix = "th"; 
if ((day % 10) == 1) { 
daySuffix = ((day / 10) == 1) ? "th" : "st"; 
} else if ((day % 10) == 2) { 
daySuffix = (day == 12) ? "th" : "nd"; 
} else if ((day % 10) == 3) { 
daySuffix = (day == 13) ? "th" : "rd"; 
} 
formater = formater.substring(0, formater.indexOf(" ")) + "'" 
+ daySuffix + "'" 
+ formater.substring(formater.indexOf(" ")); 
dateFm = new SimpleDateFormat(formater, Locale.ENGLISH); 
} else { 
dateFm = new SimpleDateFormat(formater, Locale.ENGLISH); 
} 
timePosted = dateFm.format(formatTime); 
if (caseStyle.equals("Upper")) { 
timePosted = timePosted.toUpperCase(); 
} else if (caseStyle.equals("Lower")) { 
timePosted = timePosted.toLowerCase(); 
} 
return timePosted; 
} 
public void setFormat(String format) { 
this.format = format; 
} 
public void setShowTH(String showTH) { 
this.showTH = showTH; 
} 
public void setStyle(String style) { 
this.style = style; 
} 
public void setTimestamp(String timestamp) { 
this.timestamp = timestamp; 
} 
}
三、建个jsp页面测试下:
<%@ page language="java" pageEncoding="utf-8"%> 
<%@ taglib uri="WEB-INF/tlds/formatTime.tld" prefix="tf" %> 
<html> 
<head> 
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" /> 
<title>自定义标签示例</title> 
</head> 
<body> 
<p> 
转换“20090403132233” 
</p> 
format:dd MMMM yyyy showTH:true style:Upper 转换后为:<tf:formatTimeAsString timestamp="20090403132233" format="dd MMMM yyyy" showTH="true" style="Upper"/><br/> 
format:dd MMMM yyyy showTH:true style:Lower 转换后为:<tf:formatTimeAsString timestamp="20090403132233" format="dd MMMM yyyy" showTH="true" style="Lower"/><br/> 
format:dd MMMM yyyy showTH:false style:Upper 转换后为:<tf:formatTimeAsString timestamp="20090403132233" format="dd MMMM yyyy" showTH="false" style="Upper"/><br/> 
format:dd MMMM yyyy showTH:true style:"" 转换后为:<tf:formatTimeAsString timestamp="20090403132233" format="dd MMMM yyyy" showTH="true" style=""/><br/> 
</body> 
</html>
ok了。这里timestamp是一个给定值,如果是通过${}标签动态取的话,需要将tld文件的
<attribute> 
<name>timestamp</name> 
</attribute>
修改为
<attribute> 
<name>timestamp</name> 
<rtexprvalue>true</rtexprvalue> 
</attribute>
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