Glassfish does not reuse JDBC Connections

Question

I'm using JDBC connection pooling on a glassfish webserver. I'm injecting the DataSource via this statement:

@Resource(lookup="database")
DataSource db;

The code which I'm using to load data looks something like this:

public ArrayList<Stuff> loadStuff()throws SQLException{
    PreparedStatement ps = db.getConnection().prepareStatement("Select * from stufftable");
    ResultSet rs = ps.executeQuery();
    ArrayList<Stuff> stuffs= new ArrayList<Stuff>();
    if(rs.next()){
        Stuff stuff = new Stuff();
        stuff.setString1(rs.getString("string1"));
        stuff.setString1(rs.getString("string1"));
        stuffs.add(stuff );
    }
    return stuffs;
}

For some reason glassfish is not reusing database connections, so I'm running out of them very fast. Sooner or later i'm always getting this error: Error in allocating a connection. Cause: In-use connections equal max-pool-size and expired max-wait-time. Cannot allocate more connections. Error in allocating a connection. Cause: In-use connections equal max-pool-size and expired max-wait-time. Cannot allocate more connections.

As I understood the concept of pooling on glassfish: I'm not supposed to close connections after I used them, so something else can reuse the connection when needed. Glassfish closes connection itself when there is no more demand for the connection.

Why does my program open a new connection every time? Do I have to do something with the connection when I'm done?

Answer 1

You still need to call Connection.close() . Your pool will manage your connections, so they won't really be closed, but if you don't "close" them in your code, they won't be returned to the pool.

Edit : alternatively, use a try-with-resources: https://stackoverflow.com/a/8066594/212224

Answer 2

Connection con = db.getConnection();
try {
    PreparedStatement ps = con.prepareStatement("Select * from stufftable");
    ...
} finally {
    // this returns the connection to the pool
    con.close();
}