自訂一個很簡單的JSP標籤

Web 工程，建立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;}}

建立tld檔案：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：

首先是匯入：

<%@ 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，像時鐘一樣會跳秒的。