Data Sources and JNDI

All the ConnectionPoolDataSource and DataSource implementations can be stored in JNDI. In the case of the nonpooling implementations, a new instance will be created every time the object is retrieved from JNDI, with the same settings as the instance that was stored. For the pooling implementations, the same instance will be retrieved as long as it is available (e.g., not a different JVM retrieving the pool from JNDI), or a new instance with the same settings created otherwise.

In the application server environment, typically the application server's DataSource instance will be stored in JNDI, instead of the PostgreSQL ConnectionPoolDataSource implementation.

In an application environment, the application may store the DataSource in JNDI so that it doesn't have to make a reference to the DataSource available to all application components that may need to use it. An example of this is shown in Example 11.2, " DataSource JNDI Code Example" .

Example 11.2. DataSource JNDI Code Example

Application code to initialize a pooling DataSource and add it to JNDI might look like this:

PGPoolingDataSource source = new PGPoolingDataSource();
source.setDataSourceName("A Data Source");
source.setServerName("localhost");
source.setDatabaseName("test");
source.setUser("testuser");
source.setPassword("testpassword");
source.setMaxConnections(10);
new InitialContext().rebind("DataSource", source);

Then code to use a connection from the pool might look like this:

Connection conn = null;
try
{
    DataSource source = (DataSource)new InitialContext().lookup("DataSource");
    conn = source.getConnection();
    // use connection
}
catch (SQLException e)
{
    // log error
}
catch (NamingException e)
{
    // DataSource wasn't found in JNDI
}
finally
{
    if (con != null)
    {
        try { conn.close(); } catch (SQLException e) {}
    }
}