开发动态属性标签

ゝ一世哀愁。 2021-07-24 21:10 364阅读 0赞

**一 开发自定义标签**

package lee;
    
    import javax.servlet.jsp.tagext.*;
    import javax.servlet.jsp.*;
    import java.io.*;
    import java.util.*;
    
    public class DynaAttributesTag
        extends SimpleTagSupport implements DynamicAttributes
    {
        // 保存每个属性名的集合
        private ArrayList<String> keys = new ArrayList<String>();
        // 保存每个属性值的集合
        private ArrayList<Object> values = new ArrayList<Object>();
    
        @Override
        public void doTag() throws JspException, IOException
        {
            JspWriter out = getJspContext().getOut();
            // 此处只是简单地输出每个属性
            out.println("<ol>");
            for( int i = 0; i < keys.size(); i++ )
            {
                String key = keys.get( i );
                Object value = values.get( i );
                out.println( "<li>" + key + " = " + value + "</li>" );
            }
            out.println("</ol>");
        }
    
        @Override
        public void setDynamicAttribute( String uri, String localName,
            Object value )throws JspException
        {
            // 添加属性名
            keys.add( localName );
            // 添加属性值
            values.add( value );
        }
    }

**二 建立TLD**

<?xml version="1.0" encoding="GBK"?>
    
    <taglib xmlns="http://xmlns.jcp.org/xml/ns/javaee"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
        http://xmlns.jcp.org/xml/ns/javaee/web-jsptaglibrary_2_1.xsd"
        version="2.1">
        <tlib-version>1.0</tlib-version>
        <short-name>mytaglib</short-name>
        
        <uri>http://www.crazyit.org/mytaglib</uri>
        
        <tag>
            <name>dynaAttr</name>
            <tag-class>lee.DynaAttributesTag</tag-class>
            <body-content>empty</body-content>
            
            <dynamic-attributes>true</dynamic-attributes>
        </tag>
    </taglib>

**三 使用标签**

<%@ page contentType="text/html; charset=GBK" language="java" errorPage="" %>
    
    <%@ taglib uri="http://www.crazyit.org/mytaglib" prefix="mytag"%>
    <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
        "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
    <html xmlns="http://www.w3.org/1999/xhtml">
    <head>
        <title>自定义标签示范</title>
        <meta name="website" content="http://www.crazyit.org" />
    </head>
    <body bgcolor="#ffffc0">
    <h2>下面显示的是自定义标签中的内容</h2>
    <h4>指定两个属性</h4>
    <mytag:dynaAttr name="crazyit" url="crazyit.org"/><br/>
    <h4>指定四个属性</h4>
    <mytag:dynaAttr 书名="疯狂Java讲义" 价格="99.0"
        出版时间="2008年" 描述="Java图书"/><br/>
    </body>
    </html>

**四 测试**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoZW5ncWl1bWluZw_size_16_color_FFFFFF_t_70][]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoZW5ncWl1bWluZw_size_16_color_FFFFFF_t_70]: /images/20210724/fab812d0cf274202bb3ce0a1c312a377.png