自定义标签（四）动态属性的应用

最新推荐文章于 2024-10-25 08:32:29 发布

最新推荐文章于 2024-10-25 08:32:29 发布 · 122 阅读

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#Java #JSP #Servlet #XML #SUN

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本文介绍了一个名为ListTag的自定义JSP标签的实现细节。该标签用于生成带有动态属性的HTML下拉选择框。文章展示了如何通过继承TagSupport并实现DynamicAttributes接口来创建动态属性映射，并在doStartTag方法中输出选择框元素。

ListTag.java

package tag;

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

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

/**
 * @作者 :goby
 * @创建时间：2009-6-14 上午11:19:47
 * @更新时间:$Date$
 */
public class ListTag extends TagSupport implements DynamicAttributes {
	
	public void setName(String name) {
		this.name = name;
	}

	private String name;
	private HashMap map = new HashMap();
	@Override
	public int doStartTag() throws JspException {
		// TODO Auto-generated method stub
		JspWriter out = pageContext.getOut();
		Set list = map.entrySet();
		try{
			out.print("<select name='"+name+"'>");			
Iterator it = list.iterator();
			while(it.hasNext()){
				Map.Entry entry = (Map.Entry)it.next();
				out.print("<option value='");
				out.print(entry.getKey());
				out.print("'>");
				out.print(entry.getValue());
				out.print("</option>");
			}
out.print("</select>");
		}catch(Exception ex){
			ex.printStackTrace();
		}
		return super.doStartTag();
	}

	public void setDynamicAttribute(String uri, String localname, Object value)
			throws JspException {
		// TODO Auto-generated method stub
		map.put(localname, value);
	}
	
	

}

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 web-jsptaglibrary_2_0.xsd"  
    version="2.0">

	<tlib-version>1.0</tlib-version>
	<short-name>it315</short-name>
	<uri>/taglib</uri>
		<tag>
		<name>list</name>
		<tag-class>tag.ListTag</tag-class>
		<body-content></body-content>
		<attribute>
			<description>description</description>
			<name>name</name>
			<requried>true</requried>
		</attribute>
		<dynamic-attributes>true</dynamic-attributes>
	</tag>
</taglib>

index.jsp

<%@ page contentType="text/html; charset=gb2312" %>
<%@ taglib uri="/taglib" prefix="it315" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
    <head>
        <title>Hello</title>
    </head>
    <body>
      
      <it315:list name="singer" n1="以及他很" n2="ss"/>
    </body>
</html>