自定义标签实例

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"  
              "http://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.atom.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.atom.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>