1.编写java类

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1. package myEL;  
2.   
3. public class ELFun {  
4.       
5. public static String processStr(String s) {  
6.       
7.     s=s.toUpperCase();  
8. return s;  
9.       
10. }  
11.       
12. }

EL数对应的java类的方法必须是静态的

2.编写tld文件 

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1. <?xml version="1.0" encoding="UTF-8"?>  
2. <taglib version="2.0" xmlns="http://java.sun.com/xml/ns/j2ee"  
3. xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee web-jsptaglibrary_2_0.xsd">  
4. <tlib-version>1.0</tlib-version>  
5. <uri>myelfun</uri>  
6. <function>  
7. <name>elfunction</name>  
8. <function-class>myEL.ELFun</function-class>  
9. <function-signature>  
10.      java.lang.String processStr(java.lang.String)  
11. </function-signature>  
12. </function>>  
13. </taglib>

  

TLD文件的扩展名必须是.tld

3.web.xml配置

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1. <jsp-config>  
2. <taglib>  
3. <taglib-uri>/WEB-INF/TLD/elfun.tld  
4. </taglib-uri>  
5. <taglib-location>  
6.   /WEB-INF/TLD/elfun.tld  
7. </taglib-location>  
8. </taglib>  
9. </jsp-config>

 

4.jsp中调用

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1. <%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>  
2. <%  
3. String path = request.getContextPath();  
4. String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";  
5. %>  
6. <%@ taglib uri="/WEB-INF/TLD/elfun.tld"  prefix="elfun" %>  
7. <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">  
8. <html>  
9. <head>  
10. <base href="<%=basePath%>">  
11.       
12. <title>My JSP 'elfun.jsp' starting page</title>  
13.       
14. <meta http-equiv="pragma" content="no-cache">  
15. <meta http-equiv="cache-control" content="no-cache">  
16. <meta http-equiv="expires" content="0">      
17. <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">  
18. <meta http-equiv="description" content="This is my page">  
19. <!--
20.     <link rel="stylesheet" type="text/css" href="styles.css">
21.     -->  
22.   
23. </head>  
24.     
25. <body>  
26. <form method="POST">  
27.                   请输入一个字符串：  
28. <input type="text" name="text"/>  
29. <p>  
30. <input type="submit" value ="提交"/>  
31. </form>  
32. <p>  
33.                           直接输出文本框中的内容：  
34. <p>  
35.        ${param.text }  
36. <p>  
37.       
38.      ${elfun:elfunction(param.text)}  
39. <p>  
40.       
41. <br>  
42. </body>  
43. </html>

如果用URI引用TLD文件，JSP引擎会先在WEB-INF目录及子目录中寻找所有的*.tld文件，如果发现某个.tld文件中的<uri>标签定义的URI和talib中的uri属性的值相等，就会记住这个.tld路径，在生成servlet的同时就会将这个TLD文件的路径也加进来。