自定义标记库开发之带有输入输出参数的标记开发

第一步,标签实现

1. package com.dadao.tag;
3. import java.io.IOException;
5. import javax.servlet.jsp.JspException;
6. import javax.servlet.jsp.tagext.SimpleTagSupport;
8. public class OutParamTag extends SimpleTagSupport {
9.     private Integer num;
10.     @Override
11.     public void doTag() throws JspException, IOException {
12.         this.getJspContext().setAttribute("result", num.intValue()*num.intValue());
13.         this.getJspBody().invoke(null);
14.     }
15.     public void setNum(Integer num) {
16.         this.num = num;
17.     }
18. }

第二步,修改TLD文件

1. <taglib xmlns="http://java.sun.com/xml/ns/j2ee"
2.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
3.     xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd"
4.     version="2.0">
5.    <description>oper tag  library</description>
6.    <display-name>display text</display-name>
7.    <tlib-version>1.0</tlib-version>
8.    <short-name>cy</short-name>
9.    <uri>http://mytaglib/chenyang</uri>
10.    <tag>
11.         <description>chenyang's custom display message tag</description>
12.         <name>sayHello</name>
13.         <tag-class>com.dadao.tag.HelloWorldTag</tag-class>
14.         <body-content>empty</body-content>
15.    </tag>
16.    <tag>
17.         <description></description>
18.         <name>sqt</name>
19.         <tag-class>com.dadao.tag.OutParamTag</tag-class>
20.         <body-content>scriptless</body-content>
21.         <variable><!-- 输出参数 -->
22.             <name-given>result</name-given>
23.         </variable>
24.         <attribute><!-- 定义输入参数 -->
25.             <name>num</name>
26.             <required>true</required><!-- 该参数项是必须的 -->
27.             <rtexprvalue>true</rtexprvalue><!-- 允许脚本表达式作为其值 -->
28.         </attribute>
29.    </tag>
30. </taglib>

第三步,配置.web.xml

1.   <jsp-config>
2.     <taglib>
3.         <taglib-uri>/WEB-INF/taglib/cy.tld</taglib-uri>
4.         <taglib-location>http://mytaglib/chenyang</taglib-location>
5.     </taglib>
6.   </jsp-config>

第四步，写jsp测试，代码如下：

1. <%@ page language="java"  pageEncoding="UTF-8"%>
2. <%@ taglib prefix="cy" uri="http://mytaglib/chenyang" %>
3. <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
4. <html>
5.   <head>
6.     <title>My JSP 'index.jsp' starting page</title>
7.   </head>
8.   <body> 
9.     <cy:sayHello/>
10.     <hr>
11.     <cy:sqt num="25">
12.         ${result}
13.     </cy:sqt>
14.   </body>
15. </html>