EL 表达式中使用自定义函数

一、Java

package test.utils.ctag;


public class CustomTags {
	public static boolean equals(String s1,String s2){
		if(s1==s2)
			return true;
		if(s1!=null)
			return s1.equals(s2);
		return false;
	}
}

二、TLD

<?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 web-jsptaglibrary_2_0.xsd"
	version="2.0">
	<tlib-version>1.0</tlib-version>
	<jsp-version>2.0</jsp-version>
	<short-name>f</short-name>
	<function>
		<name>equals</name>
		<function-class>test.utils.ctag.CustomTags</function-class>
		<function-signature>boolean equals( java.lang.String,
			java.lang.String )</function-signature>
	</function>
</taglib>

三、web.xml

  <jsp-config>
    <taglib>
        <taglib-uri>/functions</taglib-uri>
        <taglib-location>/WEB-INF/classes/functions.tld</taglib-location>
    </taglib>
  </jsp-config>

四、Jsp

<%@ taglib prefix="f" uri="/functions" %>

${f:equals("Hello","Hello")}<br/>
 ${f:equals("Hello","World")}<br/>
 ${f:equals(null,"World")}