core/org.eclipse.ptp.ui/src/org/eclipse/ptp/internal/ui/RMSelectionPersistence.java

/**
 * Copyright (c) 2009 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
 * 
 * Contributors:
 *     IBM Corporation - Initial Implementation
 *
 */
package org.eclipse.ptp.internal.ui;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;

import org.eclipse.ptp.core.PTPCorePlugin;
import org.eclipse.ptp.core.elements.IResourceManager;
import org.eclipse.ptp.ui.PTPUIPlugin;
import org.eclipse.ui.IMemento;
import org.eclipse.ui.WorkbenchException;
import org.eclipse.ui.XMLMemento;

public class RMSelectionPersistence 
{
	private final static String TAG_DEFAULT_RESOURCEMANAGER = "DefaultResourceManager"; //$NON-NLS-1$
	private final static String TAG_RESOURCEMANAGER = "ResourceMananger"; //$NON-NLS-1$
	private final static String TAG_RESOURCEMANAGER_ID = "ResourceManangerID"; //$NON-NLS-1$
	private final static String MEMENTO_FILE = "defaultResourceManager.xml"; //$NON-NLS-1$
	private final static String NULL_ID = "null"; //$NON-NLS-1$
	
	/**
	 * Create a resource mananger selection persistence object
	 */
	public RMSelectionPersistence()
	{
	}
	
	/**
	 * Get the default resource mananger from persistent storage
	 * 
	 * @return - the default resource mananger or null if no default resource mananger set
	 */
	public IResourceManager getDefaultRM()
	{
		File file;
		FileReader reader;
		IResourceManager rm;
		
		file = getPersistenceFile();
		reader = null;
		rm = null;
        try {
        	IMemento rmSelectionInfo;
        	IMemento child;
        	
            reader = new FileReader(file);
            rmSelectionInfo = XMLMemento.createReadRoot(reader);
            child = rmSelectionInfo.getChild(TAG_RESOURCEMANAGER);
            if (child != null) {
            	String rmID;
            	
            	rmID = child.getString(TAG_RESOURCEMANAGER_ID);
            	if ((rmID != null) && !(rmID.equals(NULL_ID))) {
            		rm = PTPCorePlugin.getDefault().getModelManager().getResourceManagerFromUniqueName(rmID);
            	}
            }
        } 
        catch (FileNotFoundException e) {
            // ignored... Default resource manager not set yet
        }
        catch (WorkbenchException e) {
            // ignored... Default resource manager not set yet
        }
        finally {
            try {
                if (reader != null) {
                    reader.close();
                }
            } catch (IOException e) {
                PTPCorePlugin.log(e);
            }
        }
		return rm;
	}
	
	/*
	 * Record the identity of the current default resource manager in persistent storage
	 * 
	 * @param rm - The default resource manager
	 */
	public void saveDefaultRM(IResourceManager rm)
	{
		XMLMemento memento;
		FileWriter writer;
		File file;
		
		file = getPersistenceFile();
		memento = createMemento(rm);
		writer = null;
		try {
			writer = new FileWriter(file);
			memento.save(writer);
		} 
		catch (IOException e) {
			PTPCorePlugin.log(e);
		} 
		finally {
			try {
				if (writer != null) {
					writer.close();
				}
			} catch (IOException e) {
				PTPCorePlugin.log(e);
			}
		}
	}
	
	/**
	 * Create the persistent data object which stores the identity of the default resource mananger
	 * 
	 * @param rm - the default resource manager
	 * @return - the persistent data object used to store the resource manager id
	 */
	private XMLMemento createMemento(IResourceManager rm)
	{
		XMLMemento memento;
		IMemento child;
		
		memento = XMLMemento.createWriteRoot(TAG_DEFAULT_RESOURCEMANAGER);
		child = memento.createChild(TAG_RESOURCEMANAGER);
		if (rm == null) {
			child.putString(TAG_RESOURCEMANAGER_ID, NULL_ID);
		}
		else {
			child.putString(TAG_RESOURCEMANAGER_ID, rm.getUniqueName());
		}
		return memento;
	}
	
	/**
	 * Get the location of the file holding the resource manager data
	 * 
	 * @return - file object for resource manager data
	 */
	private File getPersistenceFile()
	{
		final PTPUIPlugin plugin;
		
		plugin = PTPUIPlugin.getDefault();
		return plugin.getStateLocation().append(MEMENTO_FILE).toFile();
	}
}