自定义el函数

 1.编写Java类注意方法必须为static    
    package cn.syq.tag;

    public class HelloWord {
        public static String hello(){
            return "hello";
        }
        
        public static String word(int a,Integer b){
            return "word"+a+"_"+b;
        }
    }

2.在WEB-INF（子）目录下创建xxx.tld文件(文件名自定义)内容如下:
    <?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 http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd" version="2.0">

             <!-- 版本和uri必须写 -->

            <tlib-version>1.0</tlib-version>
            <uri>/eltag</uri> 
        
               <!-- 定义一个函数 -->
           <function>
               <name>hello</name>
               <function-class>cn.syq.tag.HelloWord</function-class>
               <function-signature>
                   java.lang.String hello()
               </function-signature>
           </function>
           
            <!-- 定义一个函数 -->
           <function>
               <name>word</name>
               <function-class>cn.syq.tag.HelloWord</function-class>
               <function-signature>
                   java.lang.String word(int,java.lang.Integer)
               </function-signature>
           </function>
    </taglib> 

3.在jsp文件中引入如下
    <%@ taglib uri="/eltag" prefix="eg"%>

    <input type="text" value="${eg:hello()}" />

    <input type="text" value="${eg:word(2,45)}" />