有关连接池的疑惑。

Here is an example of properly written code to use a db connection obtained from a connection pool:

Connection conn = null;
Statement stmt = null; // Or PreparedStatement if needed
ResultSet rs = null;
try {
conn = ... get connection from connection pool ...
stmt = conn.createStatement("select ...");
rs = stmt.executeQuery();
... iterate through the result set ...
rs.close();
rs = null;
stmt.close();
stmt = null;
conn.close(); // Return to connection pool
conn = null; // Make sure we don't close it twice
} catch (SQLException e) {
... deal with errors ...
} finally {
// Always make sure result sets and statements are closed,
// and the connection is returned to the pool
if (rs != null) {
try { rs.close(); } catch (SQLException e) { ; }
rs = null;
}
if (stmt != null) {
try { stmt.close(); } catch (SQLException e) { ; }
stmt = null;
}
if (conn != null) {
try { conn.close(); } catch (SQLException e) { ; }
conn = null;
}
}

以上例子引自：http://jakarta.apache.org/tomcat/tomcat-5.0-doc/jndi-datasource-examples-howto.htmlDatabase%20Connection%20Pool%20(DBCP)%20Configurations

我的问题是： conn.close(); // Return to connection pool 这一句，这个connection已经关闭了，怎么会返回连接池呢？

谢谢！