第11章 一般的なトランザクションの問題

public class TxStats
{

    // Returns the number of transactions (top-level and nested)
    // created so far.

    public static int numberOfTransactions ();

    // Returns the number of nested (sub) transactions created so far.

    public static int numberOfNestedTransactions ();

    // Returns the number of transactions which have terminated with
    // heuristic outcomes.

    public static int numberOfHeuristics ();

    // Returns the number of committed transactions.

    public static int numberOfCommittedTransactions ();

    // Returns the number of transactions which have rolled back.

    public static int numberOfAbortedTransactions ();

}

try
    {
	boolean success = false;
	AtomicAction A = new AtomicAction();
	OnePhase opRes = new OnePhase();  // used OnePhase interface
      
	System.err.println("Starting top-level action.");
      
	A.begin();
	A.add(new LastResourceRecord(opRes));
	A.add(new ShutdownRecord(ShutdownRecord.FAIL_IN_PREPARE));
      
	A.commit();
    }

public boolean set (int index, int value)
{
    boolean result = false;
    AtomicAction A = new AtomicAction();

    A.begin();

    // We need to set a WRITE lock as we want to modify the state.

    if (setlock(new Lock(LockMode.WRITE), 0) == LockResult.GRANTED)
	{
	    elements[index] = value;
	    if ((value > 0) && (index > highestIndex))
		highestIndex = index;
	    A.commit(true);
	    result = true;
	}
    else
	A.rollback();

    return result;
}

public int get (int index)  // assume -1 means error
{
    AtomicAction A = new AtomicAction();

    A.begin();

    // We only need a READ lock as the state is unchanged.

    if (setlock(new Lock(LockMode.READ), 0) == LockResult.GRANTED)
	{
	    A.commit(true);

	    return elements[index];
	}
    else
	A.rollback();

    return -1;
}