In this answer, I have shared what are static factory methods? We avoid providing direct access to database connections because they are resource intensive. So we use a static factory method getDbConnection that creates a connection if we’re below the limit. Otherwise, it tries to provide a “spare” connection, failing with an exception if there are none.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 | public class DbConnection{ private static final int MAX_CONNS = 100; private static int totalConnections = 0; private static Set<DbConnection> availableConnections = new HashSet<DbConnection>(); private DbConnection(){ // ... totalConnections++; } public static DbConnection getDbConnection(){ if(totalConnections < MAX_CONNS){ return new DbConnection(); }else if(availableConnections.size() > 0){ DbConnection dbc = availableConnections.iterator().next(); availableConnections.remove(dbc); return dbc; }else { throw new NoDbConnections(); } } public static void returnDbConnection(DbConnection dbc){ availableConnections.add(dbc); //... } } |
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