以页面片段作为属性的标签实战

￡神魔★判官ぃ 2021-07-24 12:34 276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.*;
    
    
    
    public class FragmentTag extends SimpleTagSupport
    {
        private JspFragment fragment;
    
        // fragment的setter和getter方法
        public void setFragment(JspFragment fragment)
        {
            this.fragment = fragment;
        }
        public JspFragment getFragment()
        {
            return this.fragment;
        }
        @Override
        public void doTag() throws JspException, IOException
        {
            JspWriter out = getJspContext().getOut();
            out.println("<div style='padding:10px;border:1px solid black;"
                + ";border-radius:20px'>");
            out.println("<h3>下面是动态传入的JSP片段</h3>");
            // 调用、输出“页面片段”
            fragment.invoke( null );
            out.println("</div");
        }
    }

**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>fragment</name>
            
            <tag-class>lee.FragmentTag</tag-class>
            
            <body-content>empty</body-content>
            
            <attribute>
                <name>fragment</name>
                <required>true</required>
                <fragment>true</fragment>
            </attribute>
        </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>
    <mytag:fragment>
        <jsp:attribute name="fragment">
        <%-- 使用jsp:attribute标签传入fragment参数（该注释不能放在fragment内） -->
            <%-- 下面是动态的JSP页面片段 --%>
            <mytag:helloWorld/>
        </jsp:attribute>
    </mytag:fragment>
    <br/>
    <mytag:fragment>
        <jsp:attribute name="fragment">
            <%-- 下面是动态的JSP页面片段 --%>
            ${pageContext.request.remoteAddr}
        </jsp:attribute>
    </mytag:fragment>
    </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/e063b03332e640a4bdbb82335eaf4ab2.png