ex8_23.txt

来自「j2ee core design patterns」· 文本 代码 · 共 92 行

Example 8.23 	PersistenceManager Class
import javax.transaction.*;
import java.util.HashSet;
import java.util.Iterator;

public class PersistenceManager {
	HashSet stateManagers = new HashSet();
	TransactionManager tm;
	Transaction txn;

	public PersistenceManager() {
		tm = TransactionManager.getInstance();
		tm.register(this);
	}

	public Persistable persistNew(Persistable o) {
	if (o instanceof Employee) {
		return setupEmployee(
				new EmployeeStateDelegate((Employee)o), true);
		}
		return o;
	}

	public Persistable persist(Persistable o) {
		// Must already be an EmployeeStateDelegate
		if (o instanceof Employee) {
			EmployeeStateDelegate esd =
					(EmployeeStateDelegate) o;
			return esd;
		}
		return o;
	}

	public void commit()
			throws SystemException, NotSupportedException,
			HeuristicRollbackException, RollbackException,
			HeuristicMixedException {
		if (txn == null) {
			throw new SystemException(
					"Must call Transaction.begin() before" +
					" Transaction.commit()");
		}
		Iterator i = stateManagers.iterator();
		while (i.hasNext()) {
			Object o = i.next();
			StateManager stateManager = (StateManager) o;
			stateManager.flush();
		}
		txn.commit();
		txn = null;
	}

	public void begin()
			throws SystemException, NotSupportedException {
		txn = tm.getTransaction();
		txn.begin();
	}

	public Employee getEmployee(String employeeId) {
		EmployeeStateDelegate esd =
				new EmployeeStateDelegate(employeeId);
		setupEmployee(esd, false);
		return esd;
	}

	private EmployeeStateDelegate setupEmployee(
			EmployeeStateDelegate esd, boolean isNew) {
		EmployeeStateManager stateManager =
			new EmployeeStateManager(this, esd, isNew);
		stateManagers.add(stateManager);
		esd.setStateManager(stateManager);
		return esd;
	}

	public void setDirty(Persistable o) {
		// set dirty marker to true
	}

	public void resetDirty(Persistable o) {
		// reset dirty marker to false
	}

	public boolean isDirty(Persistable o) {
		// check if object is dirty
		return true;
	}

	public boolean needLoading(Persistable o) {
		// check if needs to be loaded
		return true;
	}
}