问题
I want to use Connection pooling in my java web application with MySQL and JDBC, I found a very resource to learn at Apache Tomcat 6.0 (6.0.35) - JNDI Datasource HOW-TO,
But this example uses JSTL code to explain how to retrieve connection from pool. I want to work similarly but with a MVC architecture from scratch consisting of Beans, DAOs, Servlets and JSPs. I got everything I want from a very good DAO tutorial by BalusC but I am confused in the last part of tutorial saying How about Connection Pooling?. Could anyone please elaborate on this connection pooling topic and the close() method?
EDIT:
Actually i should have add this thing earlier also:
As the tutorial I have linked above comes before JDK7, which now has try-wth-resource code that closes the Connection automatically, then how can we maintain a Connection pool and closing a Connection in pool here with the same DAO code (or with few changes) as in the tutorial?
回答1:
if your application requires is to be used by several users one connection can be held by a connection pool so several of those users will reuse the existing connection instead of making new connection which will consume time.
about the close()method: the connection pool stays active and if you do not close a connection to it after every access,connections will pile up and if the number increases the connection pool get jammed and no longer accepts other connections!
public class MyDao {
private InitialContext context;
private DataSource datasource;
public MyDao() {
try {
Class.forName("com.mysql.jdbc.Driver");
Connection connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydb", "username", "password");
context = new InitialContext();
datasource = (DataSource) context.lookup("datasource name");
} catch (Exception e) {
JOptionPane.showMessageDialog(null, e.getMessage());
}
}
public MyBean getMyBean() throws SQLException {
Connection connection = null;
PreparedStatement statement = null;
ResultSet res = null;
String sql = "some query";
try {
connection = datasource.getConnection();//pool connection
statement = connection.prepareStatement(sql);
res = statement.executeQuery();
while (res.next()) {
//return true
}
} catch (SQLException ex) {
ex.printStackTrace();
}
finally {
if (rs!= null) try { rs.close(); } catch (SQLException logOrIgnore) {}//result set if any
if (stm!= null) try { stm.close(); } catch (SQLException logOrIgnore) {}//clase statement if any
if (connection != null) try { connection.close(); } catch (SQLException logOrIgnore) {}//close connection
}
}
}//close MyDao
来源：https://stackoverflow.com/questions/10104749/setup-connection-pooling-in-jsp-servlets-application-based-on-mvc