在Struts2中维护多个JDBC连接

Question

The number of connections to DB exceeds the permissible limit.

This is what I tried so far.

When the user successfully logs in I add one connection object to the session:

Connection conn = DatabaseConnectionManager.getConnection();
sessionMap.put("Connection", conn);

then, whenever I need a DB connection, I fetch it from the session:

Map<String, Object> sessionMap = (Map<String, Object>) ActionContext.getContext().get("session");
Connection conn = (Connection) sessionMap.get("Connection");

In the getConnection() method I print the number of times the method is called. So although I fetch the Connection object from the session why does the number of connections exceed the permissible limit which is 50 ?

JNDI Code:

Connection conn = null;         
try {
    Context initCtx = new InitialContext();
    Context envCtx = (Context) initCtx.lookup("java:comp/env");
    DataSource ds = (DataSource) envCtx.lookup("jdbc/MySqdb");
    conn = ds.getConnection();

}  
catch (NamingException ex) {
    Logger.getLogger(DatabaseConnectionManager.class.getName()).log(Level.SEVERE, null, ex);
}
catch (SQLException sqle) {
    sqle.printStackTrace();
}
System.out.println("connection: "+connection++);
return conn;

I have used JNDI. The number of connections is within the permissible limit. I'm not sure if this is the right way, please advise.

Answer 1

One connection for each user is not a good solution at all. As mentioned you must use some connection poll and if you want something simple use https://commons.apache.org/proper/commons-dbcp/ . As mentioned there:

Creating a new connection for each user can be time consuming (often requiring multiple seconds of clock time), in order to perform a database transaction that might take milliseconds. Opening a connection per user can be unfeasible in a publicly-hosted Internet application where the number of simultaneous users can be very large. Accordingly, developers often wish to share a "pool" of open connections between all of the application's current users. The number of users actually performing a request at any given time is usually a very small percentage of the total number of active users, and during request processing is the only time that a database connection is required. The application itself logs into the DBMS, and handles any user account issues internally.

You can find samples at http://svn.apache.org/viewvc/commons/proper/dbcp/trunk/doc/