I'm using GlassFish v3. The following field is declared in a class:

@Resource
private javax.sql.DataSource _data_source;

The following is declare in web.xml:

   <data-source>
        <name>java:app/env/data</name>
        <class-name>com.mysql.jdbc.Driver</class-name>        
        <server-name>localhost</server-name>
        <port-number>3306</port-number>
        <user>myUser</user>            
        <password>myPass</password>
    </data-source>

At run-time _data_source is empty. What am I doing wrong?