Closing Database Connections in Java

http://stackoverflow.com/questions/2225221/closing-database-connections-in-java

 

 

When you're done with using your Connection, you need to explicitly close it by calling its close() method in order to release any other database resources (cursors, handles, etc) the connection may be holding on to.

Actually, the safe pattern in Java is to close your ResultSet, Statement, and Connection (in that order) in a finally block when you are done with them, something like that:

Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;

try {
    // Do stuff
    ...

} catch (SQLException ex) {
    // Exception handling stuff
    ...
} finally {
    if (rs != null) {
        try {
            rs.close();
        } catch (SQLException e) { /* ignored */}
    }
    if (ps != null) {
        try {
            ps.close();
        } catch (SQLException e) { /* ignored */}
    }
    if (conn != null) {
        try {
            conn.close();
        } catch (SQLException e) { /* ignored */}
    }
}

The finally block can be slightly improved into (to avoid the null check):

} finally {
    try { rs.close(); } catch (Exception e) { /* ignored */ }
    try { ps.close(); } catch (Exception e) { /* ignored */ }
    try { conn.close(); } catch (Exception e) { /* ignored */ }
}

But, still, this is extremely verbose so you generally end up using an helper class to close the objects in null-safe helper methods and the finally block becomes something like that:

} finally {
    DbUtil.closeQuietly(rs);
    DbUtil.closeQuietly(ps);
    DbUtil.closeQuietly(conn);
}

And, actually, the Apache Commons DbUtils has a DbUtils class which is precisely doing that so there is no need to write your own.