java 自定義標籤

1、編寫**.tld文件

<?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">
	<!-- 標籤庫的版本號 -->
	<tlib-version>1.0</tlib-version>
	<!-- 標籤庫的默認前綴 -->
	<short-name>candy</short-name>
	<!-- 標籤庫的默認URI -->
	<uri>/candy</uri>

	<!-- 帶遮罩的網頁對話框標籤 -->
	<tag>
		<description>帶遮罩的網頁對話框標籤</description>
		<name>msgdialog</name>
		<tag-class>candy.tld.MsgDialogTag</tag-class>
		<!-- 標籤體可以是靜態HTML元素，表達式語言，但不允許出現JSP腳本 -->
		<body-content>scriptless</body-content>
		<attribute>
			<description>對話框標題文字,默認爲"溫馨提示"</description>
			<name>title</name>
			<required>false</required>
			<!-- 可以使用JSP表達式 -->
			<rtexprvalue>true</rtexprvalue>
		</attribute>
		<attribute>
			<description>遮罩的高度,默認爲屏幕的高度,即100%</description>
			<name>height</name>
			<required>false</required>
			<!-- 可以使用JSP表達式 -->
			<rtexprvalue>true</rtexprvalue>
		</attribute>
		<attribute>
			<description>對話框的頂部距離,默認爲300px</description>
			<name>top</name>
			<required>false</required>
			<!-- 可以使用JSP表達式 -->
			<rtexprvalue>true</rtexprvalue>
		</attribute>
		<attribute>
			<description>對話框的寬度,默認爲500px</description>
			<name>boxwidth</name>
			<required>false</required>
			<!-- 可以使用JSP表達式 -->
			<rtexprvalue>true</rtexprvalue>
		</attribute>
		<attribute>
			<description>基本URL</description>
			<name>basepath</name>
			<required>true</required>
			<!-- 可以使用JSP表達式 -->
			<rtexprvalue>true</rtexprvalue>
		</attribute>
		<attribute>
			<description>臨時ID後綴,避免ID衝突,默認爲系統時間的毫秒數</description>
			<name>tmpid</name>
			<required>false</required>
			<!-- 可以使用JSP表達式 -->
			<rtexprvalue>true</rtexprvalue>
		</attribute>
	</tag>
</taglib>

2.編寫工具類

package candy.tld;

import java.io.*;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.JspFragment;
import javax.servlet.jsp.tagext.SimpleTagSupport;

/** 帶遮罩的網頁對話框自定義標籤類 */
public class MsgDialogTag extends SimpleTagSupport {

	String title = "溫馨提示"; // 對話框標題文字
	String height = "100%"; // 遮罩的高度,默認爲屏幕的高度,即100%
	String top = "300px"; // 對話框的頂部距離,默認爲100px
	String boxwidth = "330px";// 對話框的寬度,默認爲500px
	String basepath = ""; // 基本URL
	String tmpid = null; // 臨時ID後綴,避免ID衝突,默認爲系統時間的毫秒數

	/** 標籤體處理 */
	public void doTag() throws JspException, IOException {
		// 規範屬性值
		if (!height.endsWith("%"))
			height = height + "px";
		if (!top.endsWith("px"))
			top = top + "px";
		if (!boxwidth.endsWith("px"))
			boxwidth = boxwidth + "px";
		int titlewidth = Integer.valueOf(boxwidth.replaceAll("px", ""))
				.intValue() - 22;
		if (tmpid == null)
			tmpid = String.valueOf(System.currentTimeMillis());// 臨時ID後綴,避免ID衝突

		// 取得現有標籤體的內容
		JspFragment body = this.getJspBody();
		StringWriter writer = new StringWriter();
		body.invoke(writer);

		// 構造帶遮罩的網頁對話框
		StringBuffer sb = new StringBuffer();
		sb.append("<style>\n");
		sb.append("#msgbox"
				+ tmpid
				+ "{width:"
				+ boxwidth
				+ ";background: #D6D3CE; border:1px #848284 solid;padding:0px;margin:0 auto;}\n");
		sb.append(".msgicon{float:left;background-image:url("
				+ basepath
				+ "/img/msgtitle_icon.jpg); background-repeat:no-repeat; height:20px;width:20px;}\n");
		sb.append(".msgtilte{float:left; text-align:left;background-image:url("
				+ basepath
				+ "/img/msgtitle_back.jpg); background-repeat:repeat-x;line-height:20px;letter-spacing:2px; height:20px; width:"
				+ titlewidth + "px;}\n");
//		sb.append(".msgclose{float:left;background-image:url("
//				+ basepath
//				+ "/img/btn_close.jpg); background-repeat:no-repeat; height:20px; width:20px; cursor:pointer;}\n");
		sb.append(".msgmainbox{clear:both; border-top:1px #848284 solid;text-align:left;padding:20px;overflow: auto;}\n");
		sb.append("</style>\n");
		sb.append("<div id='mask"
				+ tmpid
				+ "' style='clear:both;top:0;left:0;position:absolute;z-index:10001;filter:alpha(opacity=70);background:#000;opacity: 0.7;-moz-opacity: 0.7;height:"
				+ height + ";width:100%;'></div>\n");
		sb.append("<div id='msgprompt"
				+ tmpid
				+ "' style='clear:both;top:"
				+ top
				+ ";left:0;position: absolute; z-index: 10002; width:100%;text-align:center'>\n");
		sb.append("<div id='msgbox" + tmpid + "'>\n");
		sb.append("<div class='msgicon'></div>\n");
		sb.append("<div class='msgtilte'>" + title + "</div>\n");
//		sb.append("<div class='msgclose' onClick='closemask" + tmpid
//				+ "()'></div>\n");
		sb.append("<div class='msgmainbox'>\n");
		// 插入標籤體中的提示信息內容
		sb.append(writer.toString().trim() + "\n");
		sb.append("</div>\n");
		sb.append("</div>\n");
		sb.append("</div>\n");
//		sb.append("<script language='javascript'>\n");
//		sb.append("function closemask" + tmpid + "(){\n");
//		sb.append("document.getElementById('mask" + tmpid
//				+ "').style.display='none';\n");
//		sb.append("document.getElementById('msgprompt" + tmpid
//				+ "').style.display='none';\n");
//		sb.append("}\n");
//		sb.append("</script>\n");
		sb.append("</div>\n");
		// 輸出處理結果到頁面上
		getJspContext().getOut().println(sb);
	}

	public String getTitle() {
		return title;
	}

	public void setTitle(String title) {
		this.title = title;
	}

	public String getBasepath() {
		return basepath;
	}

	public void setBasepath(String basepath) {
		this.basepath = basepath;
	}

	public String getHeight() {
		return height;
	}

	public void setHeight(String height) {
		this.height = height;
	}

	public String getTop() {
		return top;
	}

	public void setTop(String top) {
		this.top = top;
	}

	public String getBoxwidth() {
		return boxwidth;
	}

	public void setBoxwidth(String boxwidth) {
		this.boxwidth = boxwidth;
	}

	public String getTmpid() {
		return tmpid;
	}

	public void setTmpid(String tmpid) {
		this.tmpid = tmpid;
	}
}

3.頁面導入標籤

<%@ taglib prefix="candy" uri="/candy" %>

4.頁面調用標籤

<candy:msgdialog basepath="<%=request.getContextPath()%>">
	請輸入登錄密碼解鎖：<br><br>
	<input type="text" id="passText" >
	<input type="button" onclick="valSystemLock()" value="解鎖" class="btn" style="margin-bottom: 8px;" />
	<br>
	<span id="valmsg" style="color: red;"></span>
</candy:msgdialog>

本例子以系統鎖定爲例實現自定義標籤的實現及使用。