自定義一個很簡單的JSP標籤

Web 工程，新建Java類：

package leon.webtest.tags;

import java.text.SimpleDateFormat;
import java.util.Date;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.tagext.TagSupport;


public class DateTime extends TagSupport {

	private static final long serialVersionUID = 1L;

	public int doStartTag() throws JspException {
		try {
			JspWriter out = this.pageContext.getOut();
			
			SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
			
			out.println("<span>");
			out.println(sdf.format(new Date()));
			out.println("</span>");

		} catch (Exception e) {
			throw new JspException(e.getMessage());
		}
		return SKIP_BODY;
	}
}

新建tld文件：WEB-INF/tld/webtest-tags.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:schemalLocation="http://java.sun.com/xml/ns/j2ee web-jsptaglibrary_2_0.xsd"
	version="2.0">

	<description>A tag library exercising SimpleTag handlers.</description>
	<tlib-version>1.0</tlib-version>
	<short-name>Examples</short-name>
	<uri>/MyTags</uri>
	<description>JSP Self-define Tag Library.</description>

	<tag>
		<description>This is an date time tag</description>
		<name>datetime</name>
		<tag-class>leon.webtest.tags.DateTime</tag-class>
		<body-content>empty</body-content>
	</tag>
</taglib>

web.xml中的配置：

<?xml version="1.0" encoding="UTF-8"?>
<web-app id="WebApp_ID" version="2.4" 
	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-app_2_4.xsd">
	
	<display-name>WebTest</display-name>
	
	<welcome-file-list>
		<welcome-file>index.html</welcome-file>
		<welcome-file>index.jsp</welcome-file>
	</welcome-file-list>
	
	<jsp-config>
		<taglib>
			<taglib-uri>/MyTags</taglib-uri>
			<taglib-location>/WEB-INF/tld/webtest-tag.tld
			</taglib-location>
		</taglib>
	</jsp-config>
</web-app>

JSP中的使用：

首先是導入：

<%@ taglib uri="/MyTags" prefix="leon" %>

 

使用標籤：

<leon:datetime />

 

加強版：需要顯示出來的時間是動態的，像時鐘一樣會跳秒的。