@WebService(serviceName = "download")
public class download

{


        Connection con=null;

   private DataSource getJdbcPostgres() throws NamingException, SQLException

   {
      Context c = new InitialContext();
      DataSource ds=(DataSource) c.lookup("java:comp/env/jdbc/postgres");
      con=ds.getConnection();
      return ds;
   }



@WebMethod(operationName = "download")
public String download(@WebParam(name = "username")String username, @WebParam(name = "id")String id) throws ClassNotFoundException, SQLException
{

    String sql="select * from test where id="+id;

    Class.forName("org.postgresql.Driver");

      PreparedStatement pst=con.prepareStatement(sql);
      ResultSet rs=pst.executeQuery();
      ResultSetMetaData rsmd=rs.getMetaData();
      rs.next();

  return "";
  }

}

<?xml version="1.0" encoding="UTF-8"?>
<Context path="/service2">
 <Resource name="jdbc/postgres" auth="Container"
      type="javax.sql.DataSource" driverClassName="org.postgresql.Driver"
      url="jdbc:postgresql://localhost:5432/postgres"
      username="someusername" password="somepassword" maxTotal="20" maxIdle="10"
      maxWaitMillis="-1"/>
 </Context>

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.1" xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd">
   <listener>
       <listener-class>com.sun.xml.ws.transport.http.servlet.WSServletContextListener</listener-class>
   </listener>
   <servlet>
       <servlet-name>download</servlet-name>
       <servlet-class>com.sun.xml.ws.transport.http.servlet.WSServlet</servlet-class>
       <load-on-startup>1</load-on-startup>
   </servlet>
   <servlet-mapping>
       <servlet-name>download</servlet-name>
       <url-pattern>/download</url-pattern>
   </servlet-mapping>
   <session-config>
       <session-timeout>
           30
       </session-timeout>
   </session-config>
   <resource-ref>
       <description>postgreSQL Datasource example</description>
       <res-ref-name>jdbc/postgres</res-ref-name>
       <res-type>javax.sql.DataSource</res-type>
       <res-auth>Container</res-auth>
   </resource-ref>
</web-app>

Checking data source definitions for missing JDBC drivers...
Undeploying ...
undeploy?path=/service2
OK - Undeployed application at context path /service2
In-place deployment at D:NetBeansProjectsservice2buildweb
Deployment is in progress...
deploy?config=file%3A%2FC%3A%2FUsers%2FTRAINE%7E3%2FAppData%2FLocal%2FTemp%2Fcontext1366288511044657094.xml&path=/service2
FAIL - Deployed application at context path /service2 but context failed to start
D:NetBeansProjectsservice2nbprojectbuild-impl.xml:1094: The module has not been deployed.
See the server log for details.
BUILD FAILED (total time: 2 seconds)