[163592] first cut at transaction boundary for model operations

rse/plugins/org.eclipse.rse.core/src/org/eclipse/rse/core/model/RSEModelOperation.java

@@ -0,0 +1,139 @@
+/********************************************************************************
+ * Copyright (c) 2006 IBM Corporation. All rights reserved.
+ * This program and the accompanying materials are made available under the terms
+ * of the Eclipse Public License v1.0 which accompanies this distribution, and is 
+ * available at http://www.eclipse.org/legal/epl-v10.html
+ * 
+ * Initial Contributors:
+ * David Dykstal (IBM) - initial API and implementation
+ ********************************************************************************/
+
+package org.eclipse.rse.core.model;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import org.eclipse.rse.core.RSECorePlugin;
+import org.eclipse.rse.logging.Logger;
+import org.eclipse.rse.persistence.IRSEPersistenceManager;
+
+/**
+ * Provides a transaction boundary for RSE model operations. All operations that 
+ * modify model objects should be done within an RSEModelOperation. These operations
+ * may be nested. Changes made to the model will be persisted when the outermost 
+ * operation of a particular thread is exited.
+ * <p>
+ * The usage idiom is to create an anonymous subclass of this class just prior to 
+ * use, overriding the {@link #execute()} method, and then invoke the {@link #run()} method.
+ * <pre>
+ * RSEModelOperation m = new RSEModelOperation() {
+ *     public void execute() {
+ *         ... do work here ...
+ *     }
+ * };
+ * m.run();
+ * </pre>
+ * <p>
+ * under development - provisional
+ * @since RSE 2.0
+ */
+public abstract class RSEModelOperation {
+	
+	private static Map threads = new HashMap();
+	
+	/**
+	 * Checks the current thread to see if there is a model transaction in progress.
+	 * Should be used inside model objects prior to a change to a persistent property.
+	 */
+	public static void check() {
+		if (getDepth() == 0) {
+			Logger logger = RSECorePlugin.getDefault().getLogger();
+			logger.logInfo("not inside transaction"); //$NON-NLS-1$
+		}
+	}
+
+	/**
+	 * @return the depth of the nesting for transactions in the current thread
+	 */
+	private static int getDepth() {
+		Thread myThread = Thread.currentThread();
+		if (threads.get(myThread) == null) {
+			threads.put(myThread, new Integer(0));
+		}
+		int depth = ((Integer) threads.get(myThread)).intValue();
+		return depth;
+	}
+	
+	/**
+	 * Begins a transaction. 
+	 */
+	private static void beginTransaction() {
+	}
+
+	/**
+	 * Ends a transaction. Schedules all changed profiles for save.
+	 */
+	private static void endTransaction() {
+		ISystemRegistry registry = RSECorePlugin.getDefault().getSystemRegistry();
+		ISystemProfileManager profileManager = registry.getSystemProfileManager();
+		IRSEPersistenceManager persistenceManager = RSECorePlugin.getDefault().getPersistenceManager();
+		persistenceManager.commit(profileManager);
+	}
+
+	/**
+	 * Enters a new nested level of operation.
+	 */
+	private static void enterLevel() {
+		int depth = getDepth();
+		try {
+			if (depth == 0) {
+				beginTransaction();
+			}
+		} finally {
+			Thread myThread = Thread.currentThread();
+			threads.put(myThread, new Integer(depth + 1));
+		}
+	}
+
+	/**
+	 * Leaves the current nesting level. If leaving the outermost nesting level then 
+	 * ends the transaction.
+	 */
+	private static void leaveLevel() {
+		int depth = getDepth();
+		try {
+			if (depth == 1) {
+				endTransaction();
+			}
+		} finally {
+			Thread myThread = Thread.currentThread();
+			threads.put(myThread, new Integer(depth - 1));
+		}
+	}
+
+	/**
+	 * Create a new operation scoped to the current thread.
+	 */
+	public RSEModelOperation() {
+	}
+	
+	/**
+	 * Perform the work of this operation. This is where the work of modifying several model
+	 * properties or objects can be done.
+	 */
+	public abstract void execute();
+	
+	/**
+	 * Runs this operation. This will cause the {@link #execute()} method to be invoked inside
+	 * a transaction boundary.
+	 */
+	public void run() {
+		enterLevel();
+		try {
+			execute();
+		} finally {
+			leaveLevel();
+		}
+	}
+
+}