The Java SqlLocalConnection Class

 
    public  class SqlLocalConnection extends Connection implements SqlConnection
    {
        /**
        * Constructor of the local database connection.
        * @param db opened database
        */
        public SqlLocalConnection(Database db) 
        {
            super(db);
            engine = open(id);
        }
 
 
        /**
        * Constructor of Sql connection using existed connections
        * @param con existed database connection
        */
        public SqlLocalConnection(Connection con) 
        {
            super(con);
            isCopy = true;
            engine = open(id);
        }
 
        /**
        * Execute SQL query.
        * @param query SQL query with '?' used as parameter placeholder.
        * @return cursor through selected tuples
        */
        public SqlResultSet executeQuery(String query, Object... params) 
        {
            SqlResultSet result = new SqlResultSet(this, executeQuery(engine, trans, query, params));
            results.add(result);
            return result;
        }
 
        /**
        * Execute SQL update statement
        * @param stmt SQL DML statement with '?' used as parameter placeholder.
        * @return number of affected (updated, inserted, deleted) records
        */
        public int executeStatement(String stmt, Object... params) 
        {
            return executeStatement(engine, trans, stmt, params);
        }
 
        public void startTransaction(Database.TransactionType type, 
            Database.TransactionPriority pri, Database.IsolationLevel level) 
        {
            if (nNestedTrans++ == 0) 
            {
                trans = startSqlTransaction(engine, type.ordinal(), pri.ordinal(), level.ordinal());
            }
        }
         
        public boolean commitTransaction() 
        {
            if (nNestedTrans > 0) 
            {
                if (--nNestedTrans == 0) 
                {
                    trans = 0;
                    return super.commitTransaction();
                }
                return true;
            } else 
            {
                return false;
            }
        }
 
        public void rollbackTransaction() 
        {
            trans = 0;
            nNestedTrans = 0;
            super.rollbackTransaction();
        }
 
        /**
        * Close this connection.
        */
        public void disconnect() 
        {
            if (engine != 0) 
            {
                Set<SqlResultSet> attachedResults = results;
                results = null;
                for (SqlResultSet result : attachedResults) 
                {
                    result.close();
                }
                close(engine);
                engine = 0;
            }
            if (!isCopy) 
            {
                super.disconnect();
            }
        }
 
        /**
        * Close this connection. The same as disconnect.
        */
        public void close() 
        {
            disconnect();
        }

       /** 
        * Associate current thread with this engine instance.
        */
        public void grab() {
           if (engine == 0) {
               throw new SqlException("this connection has already closed");
           }
           grab(engine);
        }
 
        public void detachResultSet(SqlResultSet result) 
        {
            if (results != null) 
            {
                results.remove(result);
            }
        }
 
        public long getEngine() 
        {
            return engine;
        }
     
        private long engine;
        private long trans;
        private int  nNestedTrans;
        private boolean isCopy;
        private Set<SqlResultSet> results = new HashSet<SqlResultSet>();;
        private native long open(long connection);
        private native long executeQuery(long engine, long trans, String query, Object[] params);
        private native int  executeStatement(long engine, long trans, String stmt, Object[] params);
        private native void close(long engine);
        private native long startSqlTransaction(long engine, int type, int pri, int level);
    };