Once we have our web.xml , we are ready to add our datasource reference. When
creating our web.xml , NetBeans automatically opens it using the built-in web.xml
We can add the resource reference by clicking on the Add... button under Resource
For our purposes, all we need to do is add a value for the Resource Name text field,
the value of this field must be the JNDI ( Java Naming and Directory Interface )
name of the data source we wish to use with our application, in our specific example,
this JNDI name is jdbc/sample .