步驟:
1. 定義tld標簽描述文件
2. 新建class繼承SimpleTagSupport或者BodyTagSupport
3. taglib命令聲明
4. 使用自定義標簽
1. 定義tld標簽描述文件custom_tag.tld
<?xml version="1.0" encoding="UTF-8"?>
<taglib xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd"
version="2.0">
<description>JSTL 1.1 core library</description>
<display-name>JSTL core</display-name>
<tlib-version>1.1</tlib-version>
<short-name>ct</short-name>
<!-- 與 taglib 的 uri 對應 -->
<uri>http://www.customtag.com/custom_tag</uri>
<!-- 定義一個標簽 -->
<tag>
<!-- 標簽的名稱 -->
<name>date</name>
<!-- 標簽類 -->
<tag-class>com.customtag.tags.DateTag</tag-class>
<!-- 標簽體 -->
<body-content>empty</body-content>
<attribute>
<!-- 屬性名稱 -->
<name>format</name>
<!-- 是否必選 true:必選 -->
<required>false</required>
<!-- 是否允許使用表達式(EL), false:不能使用 -->
<rtexprvalue>false</rtexprvalue>
</attribute>
<attribute>
<name>value</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
</tag>
</taglib>
注:
可參考jstl-[version].jar中META-INF下的c.tld文件
2. 新建DateTag繼承SimpleTagSupport或者BodyTagSupport
package com.customtag.tags;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.tagext.SimpleTagSupport;
public class DateTag extends SimpleTagSupport {
@Override
public void doTag() throws JspException, IOException {
SimpleDateFormat sdf = new SimpleDateFormat(format);
PageContext pc = (PageContext) getJspContext();
JspWriter out = pc.getOut();
try{
if(null != this.getValue()){
out.print(sdf.format(new Date(this.getValue())));
}else{
out.print(sdf.format(new Date()));
}
}catch(IOException e){
throw e;
}catch(Exception e){
out.print("");
}
}
private String format="yyyy-MM-dd HH:mm:ss";
private Long value = null;
public String getFormat() {
return format;
}
public void setFormat(String format) {
this.format = format;
}
public Long getValue() {
return value;
}
public void setValue(Long value) {
this.value = value;
}
}
3. taglib命令聲明
<%@taglib prefix="ct" uri="http://www.customtag.com/custom_tag"%>
4. 使用自定義標簽
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme() + "://"
+ request.getServerName() + ":" + request.getServerPort()
+ path + "/";
%>
<%@taglib prefix="ct" uri="http://www.customtag.com/custom_tag"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>My JSP 'index.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<body>
自定義標簽測試 :
<br>
<ct:date/><br/>
<ct:date format="MM/dd/yyyy"/><br/>
<ct:date format="yyyy年MM月dd日 HH時mm分ss秒" value="<%=new Date().getTime() %>"/><br/>
</body>
</html>
[運行結果]
自定義標簽測試:
2013-03-04 16:18:29
03/04/2013
2013年03月04日 16時18分29秒