Get database connection through application server datasource

TL;DR: To access resources defined on a JEE server, use JNDI.

Although the concepts are not complicated, the technical details have their details and it's been a long time since I have had to define these things. In any case, I think that (since there are no other answers) it is better to give you an approximate answer that may fail in some detail than not that there is no answer.

As I mentioned, your Datasource will be defined in the JNDI. It will normally be inside the namespace java: (eg java:miDataSource) or java:jboss/¹ . Through the server management console you can check the JNDI elements.

To get the data, two options:

JNDI pure and simple.

(This is also good for accessing any JNDI resource)

When you deploy/create the datasource on the server, it is assigned a JNDI name and is accessible through this service:

javax.naming.Context ctx = new javax.naming.InitialContext();
DataSource ds = (DataSource) ctx.lookup("java:miDatasource");

The name issue is somewhat messy; If I remember correctly you can directly access the "global" name ( java:) but that can cause problems; If you have two applications that use the same name for Datasources that are different, you will not be able to have them on the same server.

So in your application/webapp, what you do is indicate which Datasource you use and give the application a "local" name; for example in the jboss-web.xml:

<resource-ref>
   <res-ref-name>jdbc/miDataSourceLocal</res-ref-name><!-- nombre local -->
   <res-type>javax.sql.DataSource</res-type>
   <jndi-name>java:/miDataSource</jndi-name><!-- nombre global -->
</resource-ref>

This creates a JNDI entry for you, java:comp/env/jdbc/miDataSourceLocalwhich is the one you use in your code:

DataSource ds = (DataSource) ctx.lookup("java:comp/env/jdbc/miDataSourceLocal");

@Resource

In server-managed instances (which you don't make new, but the server creates, like e.g. Servlets and EJBs), you can use @Resourceand let the server inject the Datasource:

@Resource(name="miDataSourceLocal")
private javax.sql.DataSource myDB

This just automates your access to the JNDI, so the part about managing names to avoid collisions applies here as well.

¹ If I remember correctly, JBoss forces you to do this.

after searching and searching i find what i needed in this link http://www.javapractices.com/topic/TopicAction.do?Id=127

import java.sql.*;
import javax.naming.*; 
import javax.sql.*;

/** 
 Get a connection to a database.
 Callers need to close the connection when finished.  
*/
final class GetConnection {

  /** Preferred style, using JNDI and Datasource. */
  Connection getJNDIConnection(){
    String DATASOURCE_CONTEXT = "java:comp/env/jdbc/blah";
    Connection result = null;
    try {
      Context initialContext = new InitialContext();
      //cast is necessary
      DataSource datasource = (DataSource)initialContext.lookup(DATASOURCE_CONTEXT);
      if (datasource != null) {
        result = datasource.getConnection();
      }
      else {
        log("Failed to lookup datasource.");
      }
    }
    catch (NamingException ex) {
      log("Cannot get connection: " + ex);
    }
    catch(SQLException ex){
      log("Cannot get connection: " + ex);
    }
    return result;
  }