创建自定义的EL function(Creating a custom EL function)

测试环境： tomcat7,jdk1.7

 

1.First make a class with a static method like so:

package your.package;



public class Functions {



       public static String hello(String name) {

         return "Hiya, " + name + ".";

       }



}

 

2. Then make a file called mytaglib.tld in WEB-INF/tags/:

<?xml version="1.0" encoding="ISO-8859-1" ?>

    <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/javaee/web-jsptaglibrary_2_1.xsd" 

      version="2.1"> 



      <tlib-version>1.0</tlib-version>

      <uri>http://www.your.url/tablib_name</uri>



      <function>

          <name>hello</name>

          <function-class>your.package.Functions</function-class>

          <function-signature>java.lang.String hello(java.lang.String)</function-signature>



      </function>  



    </taglib>     

3. The uri would be used if we were accessing this directly, but instead we’ll be accessing the url from the web.xml below:

 <web-app 

        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-app_2_4.xsd"

        version="2.4">



        ...



       <jsp-config>

       <taglib>

         <taglib-uri>

           http://some.thing/mine

         </taglib-uri>

         <taglib-location>

           /WEB-INF/tags/mytaglib.tld

         </taglib-location>

       </taglib> 

       </jsp-config>



       ...



     </web-app>

4. Note we’re pointing to the mytaglib.tld file just created. And taglib-uri is how we’ll refer to it in the JSP:

    <%@ taglib uri="http://some.thing/mine" prefix="a" %> 



    ${a:hello("Aaron")}